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Tolerance to heated egg in egg allergy: Explanations and implications for prevention and treatment

Clinical and Translational Allergy

December 2023
13(12)

DOI:10.1002/clt2.12312

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CC BY 4.0

Authors:

Marie Bodinier

French National Institute for Agriculture, Food, and Environment (INRAE)

Hen's egg allergy is the second most frequent food allergy found in children. Allergic symptoms can be caused by raw or heated egg, but a majority of egg‐allergic children can tolerate hard‐boiled or baked egg. Understanding the reasons for the tolerance towards heated egg provides clues about the molecular mechanisms involved in egg allergy, and the differential allergenicity of heated and baked egg might be exploited to prevent or treat egg allergy. In this review, we therefore discuss (i) why some patients are able to tolerate heated egg; by highlighting the structural changes of egg white (EW) proteins upon heating and their impact on immunoreactivity, as well as patient characteristics, and (ii) to what extent heated or baked EW might be useful for primary prevention strategies or oral immunotherapy. We describe that the level of immunoreactivity towards EW helps to discriminate patients tolerant or reactive to heated or baked egg. Furthermore, the use of heated or baked egg seems effective in primary prevention strategies and might limit adverse reactions. Oral immunotherapy is a promising treatment strategy, but it can sometimes cause significant adverse events. The use of heated or baked egg might limit these, but current literature is insufficient to conclude about its efficacy.

Available via license: CC BY

Content may be subject to copyright.

Received: 7 August 2023

Revised: 2 October 2023

Accepted: 26 October 2023

DOI: 10.1002/clt2.12312

REVIEW ARTICLE

Tolerance to heated egg in egg allergy: Explanations and

implications for prevention and treatment

Audrey Leau |Sandra Denery‐Papini |Marie Bodinier |Wieneke Dijk

INRAE, UR BIA, Nantes, France

Correspondence

Wieneke Dijk, Impasse Thérèse

Bertrand‐Fontaine, Nantes, 44300, France.

Email: Wieneke.dijk@inrae.fr

Funding information

Institut National de Recherche pour

l'Agriculture, l'Alimentation et

l'Environnement, Grant/Award Number:

ORIA; Conseil Régional des Pays de la Loire,

Grant/Award Number: PULSAR

Abstract

Hen's egg allergy is the second most frequent food allergy found in children. Allergic

symptoms can be caused by raw or heated egg, but a majority of egg‐allergic children

can tolerate hard‐boiled or baked egg. Understanding the reasons for the tolerance

towards heated egg provides clues about the molecular mechanisms involved in egg

allergy, and the differential allergenicity of heated and baked egg might be exploited

to prevent or treat egg allergy. In this review, we therefore discuss (i) why some pa-

tients are able to tolerate heated egg; by highlighting the structural changes of egg

white (EW) proteins upon heating and their impact on immunoreactivity, as well as

patient characteristics, and (ii) to what extent heated or baked EW might be useful for

primary prevention strategies or oral immunotherapy. We describe that the level of

immunoreactivity towards EW helps to discriminate patients tolerant or reactive to

heated or baked egg. Furthermore, the use of heated or baked egg seems effective in

primary prevention strategies and might limit adverse reactions. Oral immunotherapy

is a promising treatment strategy, but it can sometimes cause signiﬁcant adverse

events. The use of heated or baked egg might limit these, but current literature is

insufﬁcient to conclude about its efﬁcacy.

KEYWORDS

baking, egg allergy, heating, oral immunotherapy, primary prevention

INTRODUCTION

Food allergy is a pathological reaction of the immune system triggered

by the ingestion of a food antigen. Exposure to very small number of

allergenic foods can trigger clinical symptoms, such as gastrointestinal

disorders, urticaria and airway inﬂammation that range in severity

from mild to life‐threatening.

Reactions can rarely be fatal and are

caused by anaphylactic shock. Food allergy prevalence and severity

seem to be increasing, and a recent analysis of European food allergy

prevalence found a life‐time overall prevalence of self‐reported

physician‐diagnosed food allergy of 6.6%.

Among the risk factors

identiﬁed for food allergies are genetics, including a family history of

allergy, having parents born in East Asia and the presence of a ﬁlaggrin

gene mutation.

Beyond genetic factors, environmental factors such as

microbial exposure, food introduction and serum vitamin D levels

modulate food allergy risk, and are likely key to the recent rise in food

allergy prevalence and severity.

Among food allergies, hen's egg allergy is the second most frequent

food allergy found in young children (~2.7% life‐time self‐reported

physician‐diagnosed, in Europe).

Most egg allergies develop in the

ﬁrst year of life and are frequently outgrown during childhood or

adolescence.

The most common symptoms of hen's egg allergy in

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, pro-

vided the original work is properly cited.

Clin Transl Allergy. 2023;e12312. wileyonlinelibrary.com/journal/clt2

1 of 24

https://doi.org/10.1002/clt2.12312

children are IgE‐mediated reactions, such as erythema, urticaria,

eczematous rash, abdominal pain, diarrhoea and vomiting.

The cur-

rent treatment for egg allergy involves strict dietary avoidance or

minimised contact with the allergen. As an alternative to an avoidance

diet, oral immunotherapy (OIT) has been investigated. OIT involves the

ingestion of small doses of egg protein by an allergic individual. This

dose is gradually increased over time to improve tolerance and further

desensitize the allergic patient. Beyond treatment strategies, primary

prevention strategies are actively studied to prevent the development

of egg allergy. These prevention strategies notably involve the early

introduction of speciﬁc forms of egg in young infants.

The main allergens of hen's eggs are found in the egg white (EW),

which consists predominantly of water and 11% proteins of over 40

different types.

The most abundant EW proteins have been identi-

ﬁed as allergens: ovomucoid (OVM) (Gal d 1, approximately 11%),

ovalbumin (OVA) (Gal d 2, approximately 54%), ovotransferrin (Gal

d 3, approximately 12%) and lysozyme (Gal d 4, approximately 3.5%)

(see Table 1).

6,7

Two allergens have also been identiﬁed in egg yolk

(serum albumin – Gal d 5, YGP42—Gal d 6), but their clinical signif-

icance remains to be further established.

21,22

OVM and OVA are the

immunodominant allergens based on speciﬁc serum IgE (sIgE) levels.

Clinical reactivity occurs towards speciﬁc amino acid sequences of

proteins, which are called epitopes. Linear epitopes are deﬁned as

continuous sequences of amino acids capable of binding IgE, whereas

conformational epitopes are formed by amino acids that are spatially

close in the protein 3D conformation but distant in the protein

sequence. Known linear and conformational epitopes of OVA and

OVM are noted in Figures 1and 2.

Allergic symptoms can be caused by the consumption of raw or

heated eggs. Nonetheless, a majority of egg‐allergic children (be-

tween 63% and 83%) can tolerate hard‐boiled or baked (>100°C)

egg.

38–40

Two phenotypes of egg‐allergic children can thus be

distinguished; patients reactive only to raw egg and patients reactive

to all forms of egg. Understanding the reasons for the tolerance of

heated egg by some but not all egg‐allergic patients might provide

clues about the molecular mechanisms involved in hen's egg allergy

sensitization and allergic reactions in general. Furthermore, the dif-

ferential allergenicity of the different forms of eggs might be

exploited to prevent or treat egg allergy. In this review, we aim to

discuss in detail (i) why some patients are able to tolerate heated egg;

by discussing the structural changes of EW proteins upon heating and

their impact on EW immunoreactivity, as well as patient

characteristics, and (ii) to what extent heated egg (white) might be

useful for primary prevention strategies or oral immunotherapy. As

OVM and OVA are the immunodominant allergens, the impact of

heating on these allergens will be discussed in detail.

WHY DO SOME PATIENTS TOLERATE HEATED

EGG?

2.1

EW heating can modify immunoreactive

epitopes and protein digestion

2.1.1

Structural characteristics of heated EW

To understand why heated eggs are better tolerated by egg‐allergic

patients, the physiochemical and structural changes occurring dur-

ing the heating of EW (proteins) need to be considered ﬁrst. Various

types of heat treatment can be applied to egg or EW to make

different food products, including egg (white) pasteurization (58–

65.5°C for 2.5–5 min for liquid egg, 55–57.2°C for liquid EW),

boiling (100°C for 5–30 min), scrambling (pan‐cooked, 4–6 min), and

baking. Baked egg is characterized by a method of cooking that uses

prolonged dry heat, normally in an oven, in the absence (e.g. oven‐

baked egg) or the presence of wheat proteins (e.g. mufﬁns or bis-

cuits). With increasing temperature, EW proteins progressively un-

fold and denature, which results in protein aggregation and

coagulation, giving heated EW its milky white colour.

Beyond ag-

gregation, heating can also induce the so‐called Maillard glycation,

which is a complex set of chemical reactions in which free amino

groups of proteins interact with the carbonyls of reducing sugars.

Maillard glycation takes place naturally in the presence of sugars but

is accelerated by heat and is frequently observed during baking and

cooking as food browning.

The progressive unfolding of egg pro-

teins and their glycation upon heating depends on (i) the time and

temperature of heating, (ii) the characteristics of the EW proteins,

and (iii) environmental factors (e.g. pH, ionic strength, the presence of

other protein sources such as wheat gluten).

EW aggregation generally starts at 60°C—the denaturation

temperature of ovotransferrin—and further accelerates at 70°C—the

denaturation temperature of OVA.

6,44

OVA contains 6 cysteine res-

idues (Cys12, Cys31, Cys74, Cys121, Cys368, and Cys383) of which

Cys74 and Cys121 form a disulphide bond in the native state.

TABLE 1Major allergens in hen's eggs.

Allergen Name Localization MW (kDa) Heat stability Digestion stability References

Gal d 1 Ovomucoid EW 28 Yes Moderate, pepsin‐sensitive but IgE epitopes remain after digestion 8–11

Gal d 2 Ovalbumin EW 44 No Yes in native form

No upon heating

9–13

Gal d 3 Ovotransferrin EW 78 No No 14,15

Gal d 4 Lysozyme EW 14 Moderate Yes, but possible precipitation upon gastro‐intestinal digestion 15–19

Gal d 5 Serum albumin Egg yolk 69 No No 18

Gal d 6 YGP42 Egg yolk 35 Yes No 20

Abbreviation: EW, egg white.

2 of 24

LEAU

ET AL.

Following heat denaturation, a hydrophobic C‐terminal region con-

taining a sulfhydryl group (Cys368) is exposed to the surface and

contributes to OVA aggregate formation.

46,47

OVA aggregation is

rapid and results in the formation of thin strands (linear aggregates)

or denser particles depending on the physicochemical conditions

used during heating (pH, ionic strength, protein concentra-

tion).

12,14,48

In contrast to the heat‐labile nature of OVA, OVM is

highly resistant to heat thanks to its conformation of three tandem

domains with intra‐but not inter‐domain disulphide bonds.

8,44,49

Only prolonged heating at temperatures above 90°C (e.g. boiling

>30 min) results in the formation of an irreversible denatured state,

indicating that OVM will remain in a natural state in more transiently

heated forms of egg.

8,50

One particular situation in which OVM does

aggregate is when OVM is heated in the presence of wheat. Indeed,

OVM solubility is markedly decreased when EW is mixed with wheat

gluten and heated, due to the formation of high‐molecular weight

complexes with gluten.

51–53

For this reason, egg baked in the pres-

ence of wheat should be clearly distinguished from other forms of

heated egg in scientiﬁc studies.

2.1.2

Heating can modify immunoreactive epitopes

The heat‐induced changes in EW proteins impact allergen epitopes.

Allergens have two types of epitopes; T‐lymphocyte epitopes that are

recognized by T‐lymphocytes following protein processing and pre-

sentation by antigen‐presenting cells, and B‐cell or IgE epitopes.

These IgE epitopes are protein regions capable of binding and cross‐

linking IgE, produced by plasma cells from memory B‐cells. Cross‐

linking of the IgE‐FcεRI complex on the surface of mastocytes or

basophils by an allergen causes their degranulation and the release of

mediators (e.g. histamine) that provoke allergic symptoms. As IgE

FIGURE 1 Overview of published epitopes for Ovalbumin (Gal d 2, OVA).

23–31

FIGURE 2 Overview of published epitopes for Ovomucoid (Gal d 1, OVM).

25,28,29,32–36

LEAU ET AL.

3 of 24

epitopes can either be linear or conformational, heat treatment might

destroy conformational epitopes or mask linear epitopes due to

protein aggregation or glycation, which might change epitope

accessibility or alternatively generate new epitopes.

The immunoreactive epitopes in OVA have been identiﬁed as a

combination of conformational and linear epitopes.

Conformational

epitopes have been localized to the regions aa41‐172 (located at the

surface of OVA) and aa367‐385

23,24

(Figure 1). Due to the heat lability

of OVA, these conformational epitopes are likely lost upon heating.

Different linear epitopes have also been identiﬁed, although with sig-

niﬁcant disparity between studies.

24–29

One linear epitope located

around aa367‐385 was highlighted by multiple studies and was

recognized by 80% of sera from egg‐allergic patients in one study,

underlining its immunological importance.

23–25,27

It is of interest to

note that this particular epitope is also in a region that aggregates and

is glycated upon heating, suggesting that this epitope might become

partially masked.

46,47

Other aggregation ‘hotspots’ for OVA have been

identiﬁed at Cys31 and Cys121, which are both in proximity to linear

OVA IgE epitopes (aa16‐30 and aa125‐134).

25,29,47

‘Hotspots’ of gly-

cation were found at Lys190 (within the epitope aa 189–199) for dry

heated samples and at Lys123 (near epitope aa 125–134) for wet

heated samples.

25,29,47,55

These structural changes of OVA epitopes

induced by heating and/or glycation lower the recognition of OVA

epitopes by sIgE of patients, as assessed using Western blot and/or

ELISA (see Table 2). Some linear epitopes do persist, as heat treatment

of OVA does not fully abolish sIgE reactivity of patient sera

(see Ta-

ble 2). Indeed, two linear epitopes (aa 229–243, 280–297) were sug-

gested to be speciﬁc for patients sensitive to extensively heated egg.

For OVM, both linear and conformational epitopes play a role in

OVM allergy and their relative importance likely differs per patient.

Some OVM‐sensitized individuals might not recognize linear epitopes

at all.

Overall, OVM heating moderately reduces serum IgE binding,

but most OVM‐reactive patients still react signiﬁcantly to heated

OVM (see Table 2). For some patients, IgE reactivity even increases

upon glycation, suggesting the appearance of novel epitopes

9,10,64

(see Table 2). As OVM does not aggregate and only irreversibly de-

natures upon prolonged heat exposure (boiling >30 min), it is likely

that many OVM IgE‐binding epitopes remain accessible in moder-

ately heated OVM and EW, although no detailed molecular studies

on OVM epitopes and heating have been performed yet. Nonethe-

less, the reduced epitope accessibility of OVA and, to a lesser extent,

OVM likely explains the reduced capacity of sIgE of egg‐allergic pa-

tients to bind to heated or baked EW (see Table 2). The length of heat

treatment seemed to be the most determinant for the loss of EW IgE

reactivity following heating, which is probably linked to the gradual

chemical modiﬁcation of linear IgE epitopes

56,57

(see Table 2).

2.1.3

Heating alters egg protein digestion and

absorption

Beyond the changes in conformational or linear epitopes, heating

also impacts the digestibility of EW proteins and their absorption.

For food allergens to trigger allergic symptoms, the allergen must

conserve at least 2 epitopes following digestion and be absorbed in

an immunologically active form across the epithelial barrier. An

extensive study that used EW heated at different temperatures and

times (56°C for 32 min; 65°C for 30 min; 100°C for 5 min) showed

that heating signiﬁcantly increased EW protein digestion.

Gastric

digestion was highest following heating at 65°C for 30 min, whereas

gastro‐intestinal digestion was highest upon heating at 100°C for

5 min.

The increased digestibility of EW following heating may at

least be partially explained by the increased digestibility of OVA

following heating.

9–13

Indeed, whereas native OVA has a high

resistance to gastric digestion, heat‐aggregated OVA is more easily

digested and the peptides that are released are different.

12,13

The

reactivity of basophils sensitized with sera from egg‐allergic patients

was also signiﬁcantly reduced but not abolished following the heat-

ing and digestion of OVA, compared to unheated, digested OVA.

9,13

In contrast to heating alone, the glycation of OVA lowers its di-

gestibility and the peptides released are different than unheated or

heated OVA.

10,65

It remains to be clariﬁed to what extent heated or

glycated OVA crosses the barrier in an immunologically active form.

Two studies indicated that the heating of OVA signiﬁcantly lowered

the amount of circulating OVA following oral gavage in mice, while

another study showed that heated OVA was unable to activate pre‐

sensitized basophils following transport across the intestinal

barrier.

9,66,67

In contrast to OVA, OVM gastro‐intestinal digestion is not

signiﬁcantly affected by heating due to its high thermal stability.

9,10

OVM is digested by gastric and gastro‐intestinal ﬂuids, but its

digestion is not complete as epitopes recognized by IgE in human

sera remain present.

8,10,11

Using basophils sensitized with sera from

egg‐allergic patients, gastro‐intestinal degradation but not heating of

OVM signiﬁcantly reduced basophil reactivity.

Glycation of OVM

also did not affect gastro‐intestinal digestion.

Heating did lower

OVM immunoreactivity following passage of the epithelial barrier

compared with native OVM, but the underlying mechanisms remain

to be clariﬁed.

Summary:

OVA is more heat labile than OVM

OVM only becomes heat labile in the presence of wheat

or upon prolonged heating (>30 min)

Heating impacts OVA conformational and some, but not

all linear epitopes

Heating has limited impact on conformational and linear

OVM epitopes

OVA sensitivity to gastro‐intestinal digestion is

increased by heating, but reduced by glycation

OVM is sensitive to gastro‐intestinal digestion, but this is

not impacted by heating or glycation

4 of 24

LEAU

ET AL.

TABLE 2IgE patient serum reactivity against native and heated EW proteins.

Protein fraction Heating Heating conditions Product

Western

blot/dot blot ELISA References

Egg patient serum IgE reactivity

EW or whole egg 4–6 min Natural, EW Scrambled EW =N/A 38,56

8–10 min 90°C Natural, EW Boiled EW ↓N/A

30 min 176°C Whole egg (1/3) þwheat

matrix/mufﬁn

Mufﬁn ↓↓ N/A

3 min 260°C Whole egg (1/3) þwheat

matrix/mufﬁn

Wafﬂe ↓↓ N/A

EW 10 min 100°C Liquid (natural) = = OVM & OVA 57

30 min 100°C ↓=OVM, ↓↓ OVA

20 min 170°C ↓=OVM, ↓OVA

Fried ↑=OVM, ↓OVA

OVA 15 min 95°C Liquid (pH 7) N/A ↓15

OVA 15 min 90°C Liquid (pH 7) N/A ↓10

96 h 50°C Dry with glucose N/A ↓

OVA 30 min 100°C Liquid ↓N/A 9

OVA 30 min 100°C Liquid (pH 9.6) N/A =/↓58

60 min 100°C Liquid (pH 9.6) N/A ↓

30 min 100°C Liquid (pH 9.6) with glucose N/A =/↓

60 min 100°C Liquid (pH 9.6) with glucose N/A ↓

OVA 6 h 80°C Liquid (pH 9) N/A ↓↓ 13

6 h 80°C Liquid (pH 5) N/A ↓

OVA 3 h 65°C Dry N/A =59

3 h 65°C Dry with mannose N/A ↓

OVA 6 h 50°C Dry with glucose N/A ↓55

OVA 10 days 37°C Dry N/A =60

10 days 37°C Dry with D‐glucose N/A =/↓

10 days 37°C Dry with D‐mannose N/A =/↓

10 days 37°C Dry with D‐allose N/A ↓↓

10 days 37°C Dry with D‐galactose N/A ↓↓

10 days 37°C Dry with L‐idose N/A ↓

OVA 30 min at 65°C Liquid = = 61

30 min at 65°C Liquid with methylglyoxal ↓ ↓

30 min at 65°C Liquid with glyoxal ↓ ↓

30 min at 65°C Liquid with butanedione = =

15 min at 95°C Liquid ↓ ↓

15 min at 95°C Liquid with methylglyoxal ↓ ↓

15 min at 95°C Liquid with glyoxal ↓↓ ↓

15 min at 95°C Liquid with butanedione ↓ ↓

OVA 6 h 80°C Liquid (pH 9) N/A ↓↓ 47

6 h 80°C Liquid (pH 9) with glucose N/A ↓↓

72 h 55°C Dry = =

72 h 55°C Dry with glucose ↓ ↓

OVM 45 min 100°C Natural (whole egg) N/A ↓50

OVM 15 min 95°C Liquid (pH 7) N/A ↓15

(Continues)

LEAU ET AL.

5 of 24

2.2

Heating lowers egg allergic reactivity

2.2.1

Heating egg lowers allergic sensitization

capacity

To explain why certain patients tolerate heated or baked egg,

multiple studies have studied how heating impacts the capacity of

EW (proteins) to sensitize or provoke an allergic reaction. For

allergic sensitization, data on the sensitization capacity of raw

versus heated egg are only available for mice studies and are

largely inconclusive. In one study, a signiﬁcant reduction of total

IgE and OVA sIgE levels was found when mice were sensitized to

heated EW, compared to raw EW.

In contrast, using a short

heating time (10 min 80°C), another study found that mice

sensitized with heated EW had signiﬁcantly higher total IgE and

OVA and OVM sIgE levels compared with raw EW

(see Table 3).

Studies using OVA to sensitize mice are more consistent and show

that mice sensitized with heated OVA (10 min at 70°C or 6 h at

80°C) have modestly lower OVA sIgE compared to mice sensitized

with native OVA

68,69

(see Table 3). Furthermore, IgG2a levels –

indicative of a shift towards a Th1 helper proﬁle in detriment of

the Th2 response – were signiﬁcantly higher in mice sensitized

with heated OVA compared to native OVA.

68–70

Interestingly, the

sensitization capacity of heated OVA was found to be dependent

on the aggregation process: small, linear aggregates of OVA

formed at pH 9 (near natural pH of stored EW) and low ionic

strength displayed a reduced allergic potential compared to large,

spherical agglomerated aggregates formed at pH 5 and high ionic

strength.

Only few studies have investigated the impact of glycation on the

sensitization capacity of OVA. Two studies showed a reduction in

serum IgE levels following the sensitization of mice with glycated OVA

compared with native OVA.

67,71

In contrast, a more recent study using

heavily glycated OVA showed increased IgE levels and a stronger

reduction in body temperature compared with intraperitoneal sensi-

tization with native OVA.

These opposing results are likely due to

the extent of glycation and the heating temperature used to glycate

OVA in the different studies and further studies are needed to clarify

the impact of the extent of glycation on sensitization to OVA (Table 3).

No data on allergic sensitization of heated and/or glycated OVM

versus native OVM are currently available.

2.2.2

Heating egg lowers egg allergic reactions

Numerous mice studies have investigated the capacity of heated EW

(protein) to elicit allergic symptoms (see Table 3). In accordance with

the observations in patients, all studies demonstrated a reduction in

allergic symptoms when mice are sensitized and/or elicited with

heated EW (protein)

9,54,66,67,69,70

(see Table 3). Pablos‐Tanarro and

colleagues used an extensive cross‐over design in which mice were

sensitized to native or heated EW and provoked with either native or

heated EW.

In this study, provocation with heated EW resulted in

lower allergic symptoms in all mice compared to native EW, while the

combined sensitization and provocation with heated EW resulted in

the lowest overall clinical symptoms.

In line with these studies, the

reactivity of basophils sensitized with sera from egg‐allergic patients

or sensitized mice was signiﬁcantly reduced upon exposure to heated

OVA or OVM, when compared to the native protein (see Tables 3and

4). No studies have, to our knowledge, investigated the elicitation

capacity of glycated OVA or OVM in mice or using basophils.

When the elicitation capacity was studied in a clinical setting,

several studies showed that the wheal diameter of patient skin‐prick

tests (SPT) using baked egg in the presence (mufﬁn) or absence (oven‐

baked) of wheat was generally smaller when compared to raw

73,74

(see Table 4). Similarly, using hard‐boiled egg, EW or egg

yolk, part of children responsive to raw egg forms were not

responsive any more in SPT (43% (egg), 33% (EW) or 72% (egg

yolk)).

Pasteurization of egg or EW did not signiﬁcantly affect SPT

size, and only very few raw egg reactive patients became non‐

reactive upon pasteurization

(see Table 4).

In oral food challenges (OFC) that investigate the clinical reactivity

proﬁle of egg‐allergic patients, a direct comparison of the reactivity

towards baked/heated and uncooked eggs is generally not made (see

Table 4). Instead, a patient who reacts to baked or heated egg is

considered to react also to raw egg.

38,76–79

These studies indeed show

that a signiﬁcant percentage of patients with a negative challenge to

baked egg react to raw egg or a regular egg product (e.g. scrambled

TABLE 2(Continued)

Protein fraction Heating Heating conditions Product

Western

blot/dot blot ELISA References

OVM 15 min 90°C Liquid (pH 7) N/A ↓10

96 h 50°C Dry with glucose N/A ↑

OVM 30 min 100°C Liquid =N/A 9

OVM 48 h 60°C Dry with

galactooligosaccharide

N/A ↓62

48 h 60°C Dry with

fructooligosaccharide

N/A =

48 h 60°C Dry with mannosan N/A =

Note: Samples in grey are samples heated in the presence of sugars.

Abbreviations: EW, egg white; OVA, ovalbumin; OVM, ovomucoid.

6 of 24

LEAU

ET AL.

TABLE 3Allergy sensitization and allergic reactions against native and heated EW proteins in mice studies.

Protein fraction

Heating

conditions

Protein

conditions Structure sIgE levels (vs. Native) IgG levels (vs. Native) Mice Sensitization References

Allergic sensitization

Mouse

EW 5 min 100°C Liquid Aggregate ↓(OVA) N/A Heterozygous OVA23–3 Oral

Powder in food, heated and native

15 min 80°C Aggregate ↓(OVA) N/A

40 min 121°C Aggregate ↓(OVA) N/A

EW 10 min 80°C Liquid HMW aggregate ↑(OVA, OVM) ↓(OVA, OVM) IgG1 BALB/c Oral

Gavage with heated and native OVA þCT

OVA 10 min 70°C N/S Aggregate ↓ ↑ IgG2a, ↑IgG1 BALB/c I.p. 68

OVA 6 h 80°C pH 9, liquid Small linear aggregates ↓ ↑ IgG2a, =IgG1 BALB/cJ I.p. 69,70

6 h 80°C pH 5, liquid Large aggregates =↑IgG2a, =IgG1 BALB/cJ I.p.

Protein

fraction Heating conditions

Protein

conditions Structure Symptoms (vs. Native) Mice Sensitization Provocation References

Allergic reaction

Mouse

EW 5 min 100°C Liquid Aggregate ↓intestinal inﬂammation, diarrhoea Heterozygous

OVA23–3

Oral

Powder in food, heated and

native

N/A 67

15 min 80°C Aggregate ↓intestinal inﬂammation, diarrhoea

40 min 121°C Aggregate,

glycated

↓intestinal inﬂammation, diarrhoea

EW 10 min 80°C Liquid HMW

aggregate

Provocation with native :=Clinical

symptom score

BALB/c Oral

Gavage with heated and

native OVA þCT

Oral and i.p

Heated and

native OVA

Provocation with heated: ↓clinical

symptom score

OVA 15 min 100°C Liquid Aggregate ↓symptoms (maintenance of

voluntary wheel running)

BALB/c I.p.

Native OVA

Oral gavage

Heated OVA

OVA 10 min 70°C N/S Aggregate ↓diarrhoea

↓mMCP1

BALB/c I.p.

Heated and native OVA

Oral gavage

Heated and

native OVA

OVA 30 min 100°C Liquid N/A ↓clinical symptoms (temperature) C3H/HeJ Oral

Gavage with native

OVA þCT

Oral gavage

Heated OVA

(Continues)

LEAU ET AL.

7 of 24

TABLE 3(Continued)

Protein

fraction Heating conditions

Protein

conditions Structure Symptoms (vs. Native) Mice Sensitization Provocation References

OVA 6 h 80°C pH 9, liquid Small linear

aggregates

↓ear thickness, mMCP1 BALB/cJ I.p.

Heated OVA, pH 9

Oral gavage

Native OVA

69,70

6 h 80°C pH 5, liquid Large

aggregates

=Ear thickness, mMCP1 BALB/cJ I.p.

Heated OVA, pH 5

Oral gavage

Native OVA

OVA 2 or 7 days at 50°C at 65% humidity in the

presence of glucose

Dry Polymers ↓IgE levels dYY I.p.

Native and glycated OVA

N/A 71

OVA 6 weeks 50°C in the presence of glucose Liquid N/A ↑IgE levels

↑clinical symptoms (temperature)

BALB/c I.p.

Native OVA and glycated

OVA

Oral gavage

Native OVA

OVM 30 min 100°C Liquid N/A ↓clinical symptoms (temperature) C3H/HeJ Oral

Gavage with native

OVM þCT

Oral gavage

Heated OVM

Protein fraction Heating Heating conditions Species Basophil reactivity References

Basophil reactivity

Mouse

OVA 10 min 70°C N/S Mouse =Basophil mediator release 68

10 min 95°C N/S Mouse ↓basophil mediator release

OVA 6 h 80°C Liquid (pH 5) Mouse ↓↓ basophil mediator release 70

OVM 30 min 100°C Liquid Mouse =Basophil activation 9

Note: In grey: protein samples heated in the presence of sugars.

Abbreviations: CT, cholera toxin; EW, egg white; I.p., intraperitoneal; N/S, not speciﬁed; OVA, ovalbumin; OVM, ovomucoid.

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TABLE 4IgE patient serum reactivity against native and heated EW proteins.

Protein fraction Heating Heating conditions Species Basophil reactivity References

Basophil reactivity

Human

OVA 30 min 100°C Liquid Human =Basophil activation

↓After passage Caco‐2 barrier

OVA 6 h 80°C Liquid (pH 9) Human ↓↓ Basophil mediator release 13

6 h 80°C Liquid (pH 5) Human ↓↓ Basophil mediator release

OVM 30 min 100°C Liquid Human =Basophil activation

↓After passage Caco‐2 barrier

Protein fraction Heating Heating conditions Product SPT

Patient

characteristics References

Skin prick tests

Whole egg 180°C for 20 min Whole egg (1/6

)þwheat matrix Mufﬁn ↓or =dependent on patient, compared to EW 74

EW, egg yolk, or

whole egg

200°C for 25 min EW, egg yolk, or whole egg baked in

an oven

↓compared to uncooked egg 36 children with egg

allergy

EW, egg yolk, or

whole egg

94°C for 18 min Hardboiled egg, EW, or egg yolk ↓↓ for 43% (egg), 33% (EW), 72% (egg yolk) of children, =for the rest of

children for egg and EW, ↓for egg yolk

54 children with egg

allergy

66°C for 6 min Pasteurized egg =/↓compared to raw egg

56°C for 6 min Pasteurized EW =/↓compared to raw egg

Protein

fraction Heating Heating conditions Product Outcomes Patient characteristics References

Oral food challenges

EW 90°C for 60 min Liquid EW Unheated or heated EW preparations

(cum. dose 8 g), mixed in 50 mL of a

thick liquid vehicle consisting of the

fruit juices

21 of 38 subjects with positive challenge

responses to freeze‐dried EW had

negative challenge responses to

heated EW.

72 participants with high IgE antibody

titres to EW (a percent binding value

that was higher than 3.1% in the

RAST assay)

EW 90°C for 60 min Liquid EW Unheated or heated EW preparations

(cum. dose 8 g) mixed in 50 mL of a

thick liquid vehicle consisting of the

fruit juices

29 children with a positive challenge to

freeze‐dried egg had a negative

challenge to heated EW. All heated

EW responsive children were

considered to be responsive also to

freeze‐dried eggs.

108 children with suspected egg allergy 77

(Continues)

LEAU ET AL.

9 of 24

TABLE 4(Continued)

Protein

fraction Heating Heating conditions Product Outcomes Patient characteristics References

Whole egg 176°C for 30 min

(mufﬁn) or 260°C for

3 min (wafﬂe)

Whole egg (1/

)þwheat

matrix/mufﬁn or

wafﬂe

The ﬁrst mufﬁn, then wafﬂe. Each

divided into 4 equal doses (total cum.

dose =2.2 g of protein)

Of 117 oral food challenges to BE, 87

patients were tolerant to BE and 27

reacted. Of the 87 tolerant patients,

39 reacted to a regular egg product

in a follow‐up challenge.

117 patients with a clinical history of egg

allergy between the ages of 0.5 and

25 years.

Not speciﬁed Not speciﬁed Scrambled egg or French toast (total

cum. dose 6.5 g of protein)

Whole egg 180°C for 20 min Whole egg þwheat

matrix

Sponge cake or uncooked egg

(pasteurized). Sponge cake: 5

incremental doses (0.4 g, 0.8 g, 1.5 g,

3 g, 6 g =cum. dose ap‐proximately

1.0 g protein). Uncooked egg: 5

incremental doses (0.5 g, 1 g, 2 g, 6 g,

12 g =cum. dose approximately 2.6 g

protein)

28/77 (37%) of well‐cooked egg and 61/

104 (59%) of uncooked egg

challenges were positive

95 children with a type‐1

hypersensitivity reaction to egg and/

or SPT weal diameter ≥3 mm to

whole egg extract, and/or serum egg‐

white‐speciﬁc IgE ≥0.35 kU/L

EW 90°C for 10 min Boiled A starting dose of 0.12 g EW protein,

with doses doubled consecutively

(0.24–0.48–0.96–1.9 g) with hourly

intervals until signs appeared (cum.

dose 3.7 gEW protein)

50/85 children reacted to heated EW. Of

the 35 non‐responsive children, 14

children reacted to unheated EW.

85 children aged 5–18 years on follow‐

up for IgE‐mediated egg allergy, with

positive sIgE(>0.35 kU/L) or SPT

(>3 mm) to EW, OVA or OVM

Abbreviations: BE, baked egg; EW, egg white; OVA, ovalbumin; OVM, ovomucoid.

10 of 24

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ET AL.

egg)

38,76–79

(see Table 4). Given the more complex composition of the

foods tested in SPT, the relative impact of heating versus glycation is

difﬁcult to be determined in these studies. Taken together, the heating

or baking of EW (proteins) signiﬁcantly lowers the capacity to provoke

an allergic reaction, with the most pronounced changes observed after

prolonged heating. Given the heat stability of OVM, it is likely that part

of the residual immunoreactivity of heated EW is due to the recogni-

tion of OVM and not OVA. In support for a role of OVM in reactions

towards heated egg, a part of patients responsive to heated egg was

able to consume heated eggs depleted of OVM.

Summary:

OVA heating lowers its sensitization capacity, while the

impact of OVM heating or OVA/OVM glycation on

sensitization capacity remains to be further investigated

Heating of EW (proteins) lowers its capacity to induce an

allergic reaction in mice

Heated or baked egg white (proteins) has a lower sIgE

binding capacity and lower SPT wheal diameter

compared to raw egg

A signiﬁcant proportion of egg‐allergic patients irrespon-

sive to heated/baked egg (white) react to raw egg in OFC

The impact of heating or baking on allergic reactivity is

dependent on the time and temperature of heating

2.3

Patient reactivity to heated/baked EW and

patient prognostics depend on the sIgE sensitization

proﬁle

The previous sections highlight that heating has a signiﬁcant impact

on the sensitization capacity and allergic reactivity of EW by altering

EW structure and digestion. However, to understand why certain

patients react to heated egg whereas others do not, we also need to

look at the patients' clinical proﬁles. Several studies have attempted

to address this question. One recurrent and conﬁrmed observation is

that patients reactive to both heated and raw eggs are characterized

by higher overall sIgE levels of EW, OVA and OVM and by larger

wheal sizes following SPTs compared to patients responsive only to

raw egg.

38,40,80–83

Similarly, reactivity threshold doses for children

allergic to raw but not baked egg are higher than for the general

population of egg allergic children.

These observations suggest that

the severity of egg allergy might be a determinant factor for being

tolerant or reactive to heated eggs. However, although elevated sIgE

has a predictive value for the classiﬁcation of patients, no general-

izable cut‐offs for SPTs or sIgEs have been agreed upon so far and an

OFC using heated or baked egg remains the gold standard.

82,83,85,86

Given the heat stability of OVM, several studies have suggested

that the sIgE levels of OVM might be used to discriminate patients

responsive or tolerant to heated egg.

40,77,80,87,88

However, other

studies have not conﬁrmed a predictive value of OVM sIgE levels and

no cut‐off for patient classiﬁcation on the basis of OVM sIgE is

currently available.

82,86

One factor that might explain the discrep-

ancy between studies is the usage of heated egg versus baked egg

due to the aggregation of heated OVM in the presence of wheat.

51,82

However, to what extent the presence of wheat inﬂuences clinical

reactivity to OVM in patients remains to be further established. A

study that orally challenged egg‐sensitized individuals with different

food matrices suggested that the presence of wheat was only

important in a minority of the patients and that the duration of egg

heating (10 min vs. 30 min) was more determinant for a clinical re-

action.

Beyond the magnitude of egg sIgE levels or OVM sIgE

levels, a higher reactivity to linear epitopes (that are less heat‐

altered) in patients reactive to heated egg might also play a role.

This type of information is, however, not obtained by measurement

of sIgE binding to the entire allergen and speciﬁc epitopes that might

predict the tolerance or not to heated egg would need to be

conﬁrmed.

2.3.1

Patient prognostics

Beyond contributing to the quality of life of egg‐allergic patients, a

patient classiﬁcation based on responsiveness to heated eggs might

be useful to anticipate patient prognostics. As mentioned, many pa-

tients will outgrow hen's egg allergy, with a resolution of approxi-

mately 50% at the age of 2.

The ability to tolerate baked egg is

predictive of the transiency of egg allergy; patients unable to tolerate

baked egg are ﬁve times less likely to develop tolerance.

In line with

the characteristics distinguishing baked egg‐tolerant from reactive

patients, it has been proposed that patients who have higher sIgE to

raw EW, that are sensitized to OVM or multiple egg allergens and

that are highly reactive to linear epitopes of OVM or OVA are less

likely to outgrow their egg allergy.

33,86,90,91

Summary:

Patients reactive to both heated and raw eggs are

characterized by higher overall sIgE levels to EW, OVA

and OVM compared to patients responsive only to raw

egg

Tolerance to baked egg is predictive of the transiency of

egg allergy; patients unable to tolerate baked egg are ﬁve

times less likely to develop tolerance

USE OF HEATED EGG FOR PRIMARY

PREVENTION AND TREATMENT OF EGG ALLERGY

Given the prevalence of egg allergy, a large number of studies have

investigated primary prevention or treatment strategies. These

studies are different, both in their protocols and in their results, but

LEAU ET AL.

11 of 24

also notably in their usage of different forms of eggs to achieve

tolerance; for example, raw or heated egg (white). The different

structure and immunological reactivity of the different forms of eggs

make it of interest to assess whether and to what extent the primary

prevention and treatment of egg allergy is impacted by the form in

which the egg allergen is provided.

3.1

Use of heated egg for primary prevention of

egg allergy

One well‐studied approach to prevent egg allergy in infants is the early

introduction of egg proteins during early food diversiﬁcation (at 4–

8 months of life).

92–97

Several randomized controlled trials have been

conducted to evaluate the efﬁcacy of an early introduction of egg in

infants to prevent egg allergy using different types and doses of egg

proteins, and different patient populations (general population, high

risk) (see Table 5). In these studies, the most commonly used form of

egg was pasteurized raw egg (white) powder, which has equivalent

allergenic properties compared to raw egg

(see Table 5). Other

studies used heated egg powder or boiled egg (see Table 5). A sys-

tematic review and meta‐analysis

assessed the combined effect of

the early introduction versus no early introduction of egg protein and

the risk of developing an egg allergy in these randomized controlled

trials. It concluded to an overall signiﬁcant protective effect of early

introduction of egg protein with a decreased relative risk of developing

an egg allergy in the egg group versus control group of 0.60 (CI: 0.44–

0.82). It is, however, important to note that a signiﬁcant number of

adverse reactions (31%,

6.1%,

8.1%,

7.1%

) was described,

notably in studies using pasteurized raw egg (white) powder. In

contrast, the PETIT study, which used heated egg powder, did not

describe any adverse events.

The incidence of adverse reactions

might also be impacted by the daily dose of egg protein given, which

was high in the STAR study

that described a high incidence of adverse

reactions, and low in the PETIT study.

Beyond the safety proﬁle, the

efﬁcacy might also be impacted by the type or dose of egg used, but

none of the studies directly compared the use of different types of eggs

in primary prevention. Nonetheless, it is clear that heated egg—with its

good safety proﬁle—is able to successfully prevent the development of

egg allergy,

95,97

whereas the studies using pasteurized egg (white)

powder gave more heterogeneous results (see Table 5). In line with

this, an observational study noted that exposure to cooked egg

(deﬁned as boiled, scrambled, fried, or poached) but not to baked egg

(deﬁned as egg‐containing cakes or biscuits or similar products)

induced the development of oral tolerance: at 4–6 months of age, the

ﬁrst exposition to cooked eggs reduced the risk of egg allergy

TABLE 5Randomized controlled primary intervention trials for egg allergy.

Study

name Population Form of egg Dose Primary outcome Main result Reference

STAR 86 infants with

moderate‐

to‐severe

eczema

Pasteurized raw

egg powder

0.9 g of egg protein per day Egg allergy on oral

challenge and

positive SPT to egg

A non‐signiﬁcant reduction of

IgE mediated egg allergy in

the egg group compared

with the control group

EAT 1303 infants

from

general

population

Cooked egg

(together with

5 other types

of allergens)

2 g/week Food allergy following

oral food challenge

Intention‐to‐treat analysis: a

non‐signiﬁcant reduction of

egg allergy in the early

introduction group.Per‐

protocol analysis: a

Signiﬁcant reduction of egg

allergy in the early

introduction group.

STEP 820 infants

with

hereditary

risk

Pasteurized raw

whole egg

powder

0.4 g of egg protein per day Egg allergy on oral

challenge and

positive SPT to egg

A non‐signiﬁcant reduction of

IgE mediated egg allergy in

the egg group compared

with the control group

BEAT 319 infants

with

hereditary

risk

Pasteurized raw

whole egg

powder

0.35 g of egg protein per day Sensitization to white

egg based on SPT

A reduction in the proportion

of infants sensitized to EW

in the egg group compared

with the control group

HEAP 380 infants

from

general

population

Pasteurized EW

powder

2.5 g per week, 3 times a week

(equivalent to 0.83 g of egg

protein 3 times a week)

Sensitization to hen's

egg, based on

increased speciﬁc

serum IgE levels

A non‐signiﬁcant augmentation

of egg sensitized infants in

the egg group

PETIT 147 infants

with

eczema

Heated egg

powder

50 mg of heated egg powder

(equivalent to 25 mg of egg

protein and 0.2 g of boiled

egg), then 250 mg per day

of egg powder

Egg allergy on oral food

challenge

A signiﬁcant reduction of egg

allergies in the egg group

compared with the control

group

Abbreviation: EW, egg white.

12 of 24

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ET AL.

compared with the exposition to baked eggs (OR, 0.2 [95% CI, 0.06–

0.71]).

100

Based on these data, it might thus be hypothesized that for

the effective prevention of egg allergy, the exposition of an infant to

egg epitopes should be high enough to induce tolerance but also low

enough to not sensitize or provoke an allergic reaction. This balance

might be modiﬁed not only by the dose of egg used but also by the form

of egg protein given. Indeed, as discussed in Section 2, the heating of

EW protein modiﬁes the accessibility of linear and conformational

epitopes and increases its digestibility.

The choice of the egg form to introduce into an infant's diet is of

particular importance as a signiﬁcant proportion of infants are already

sensitized to eggs before food diversiﬁcation.

94,96

How these infants

are sensitized to egg is not fully clear, but their sensitization might

have occurred in utero through the transfer of small doses of antigen in

breast milk or through a defective skin barrier (for example due to the

presence of egg protein in dust).

101,102

Recent studies have suggested

that the exposition of infants to egg‐derived allergens and egg‐speciﬁc

IgG in breast milk might contribute to the development of oral toler-

ance and a lower egg allergic risk in infants.

103,104

An on‐going ran-

domized controlled trial now aims to determine whether a higher

maternal egg and peanut consumption during pregnancy and lactation

might prevent the development on infant egg and peanut allergy.

105

Summary:

Heated egg might be the best form to prevent the

occurrence of egg allergy, given its efﬁcacy and safety

proﬁle. For this reason, the S3 guideline Allergy Pre-

vention now recommends “For prevention of hen’s egg

allergy, well‐cooked (e.g., baked or hard‐boiled), but no

“raw” eggs (…) should be introduced with the comple-

mentary food and given regularly.”.

106

3.2

Use of heated egg for egg allergy treatment:

OIT

OIT is a potential treatment for egg allergy, consisting of the pro-

gressive reintroduction of the allergy‐causing food. It includes an

induction phase (IP) during which the ingested dose increases pro-

gressively to reach a target dose, and a maintenance phase (MP)

during which the allergen is taken regularly. The IP often starts with

an initial escalation phase with increasing doses of allergen given

every 20–30 min during a day or two under clinical supervision to

determine the starting dose for the IP. Patients undergoing an OIT

can achieve desensitization and sometimes achieve maintained

tolerance. Desensitization refers to the ability to ingest a food

without reaction while continuing to take regular doses of that food,

whereas maintained tolerance is the ability to tolerate a food after a

period of food avoidance. The maintained tolerance is assessed by

performing an oral food challenge (OFC) after discontinuing the

ingestion of the allergen for a period of at least 4 weeks.

Many studies have investigated the effectiveness of OIT in egg

allergy, including randomized controlled trials, uncontrolled trials,

and observational studies. We will focus here on 15 randomized

controlled trials (see Table 6). Although many of these studies

included only a few patients, the data provided by these studies

indicate that the efﬁcacy of egg allergy OIT is generally very good,

although mild‐to‐moderate adverse events are very frequent (see

Table 6). This observation was conﬁrmed by a meta‐analysis that

included 10 randomized controlled trials and concluded to the efﬁ-

cacy of OIT compared with a control group: most children (82%) in

the OIT group could ingest a partial serving of raw or undercooked

egg (1–7.5 g) compared to 10% of control group children.

123

It should

be noted, however, that in the different studies the inclusion criteria,

dosage, target dose, and the duration of the IP and MP are diverse

(see Table 6). Especially dosing and frequency of exposition seem

quite important for tolerance induction, as demonstrated in the

SEICAP study that compared two protocols of OIT.

115

In this study,

one group increased their daily egg intake with 5% and their weekly

intake with 30%, whereas a second group had only a 30% weekly up‐

dosing; the ﬁrst pattern was more effective than the second.

115

Different types of eggs were used in the different OIT trials (see

Table 6). In general, most studies used a rather ‘native’ form of egg

(white) for OIT trials, such as dehydrated egg, pasteurized egg (white)

powder or liquid, or raw hen's egg emulsion. Dehydrated egg powder

was most commonly tested and generally compared to a control

group having either a placebo or an egg avoidance diet. Although

different protocols were used, in all of these studies OIT was asso-

ciated with an increased percentage of desensitization and main-

tained tolerance compared with the control group (see Table 6). One

study that did not show efﬁcacy used a low‐allergenic hydrolysed

form of egg, but this study also did not use dose increments.

122

Two

randomized controlled trials speciﬁcally assessed the efﬁcacy of

baked egg consumption to induce oral tolerance in egg‐allergic pa-

tients,

116,119

as did one non‐randomized clinical trial.

124

Indeed,

earlier studies suggested that the regular ingestion of baked egg in

egg allergic children could accelerate the development of egg toler-

ance.

5,125

In a small, non‐randomized clinical trial, the incremental

ingestion of baked egg (from 125 mg to 3.8 g of baked egg daily) was

shown to induce progressive desensitization to baked egg and lightly

cooked egg (cooking conditions not speciﬁed).

124

Importantly,

compared to other OITs, only very few adverse events were re-

ported.

124

In contrast, in a randomized clinical trial that included a

control group of egg‐avoiding patients, the regular ingestion of the

same dose of 10 g of baked egg (equivalent to 1.3 g egg protein) for

6 months did not increase the proportion of patients who were able

to pass an OFC to raw egg 1 month after ceasing the intervention.

119

No signiﬁcant differences in adverse events were reported between

the baked egg‐consuming group and the control group.

119

This study

did, however, not use dose increments and cannot be ofﬁcially clas-

siﬁed as an OIT trial. Similarly, another randomized clinical trial

assessed the efﬁcacy of regular baked egg consumption (equivalent

LEAU ET AL.

13 of 24

TABLE 6Randomized controlled OIT trials for egg allergy.

Ref. Population Control Type of egg Dose Duration Primary outcome

Efﬁcacy of

desensitization

Efﬁcacy of

maintained

tolerance Adverse events

Dried powdered egg, pasteurized raw egg (white), dehydrated egg

107 45 egg or milk

allergic

children

(including 11

egg exposed

and 10 egg

controls)

Egg avoidance

diet

Lyophilised egg

powder

IP: Starting dose of

0.006 mg of egg

protein, then

dose increased

based on indi-

vidual tolerance

to reach

2800 mg of egg

protein

MP: Minimum daily

maintenance of

1600 mg egg

protein.

IP: 67 days at least

MP: 21 months

Egg avoidance: 2 months

N/A N/A OIT: 36% showed

permanent

tolerance, 12%

were tolerant

with regular

intake 16% were

partial

responders and

36% didn't

complete the

treatment

because of

adverse events.

Control: 35%

were tolerant at

the end of the

study.

All OIT children had

mild or moderate

side‐effects.

108,109 55 egg‐allergic

children

Placebo, then

OIT after

2 years

Raw EW powder IP: Initial day

escalation starts

with 0.1 mg of

powder to reach

at least 3 mg,

then daily

ingestion of

powder to reach

2 g of powder.

MP: Up to 2 g of

egg‐white

powder per day.

IP: 10 months maximum

MP: 2 months at least

and 4 years or until

sustained unrespon-

siveness is reached.

Avoidance diet: 4–

6 weeks before an

OFC.

Induction of sustained

unresponsiveness

on OFC with 5 g

or 10 g of EW

powder.

Desensitization at

10 months (OFC,

5 g):

Control: 0%

OIT: 55%

At 22 months: (OFC

10 g)

Control: 0%

OIT: 75%

4–6 weeks of avoid-

ance diet if OFC

at 22 was passed:

28% of the chil-

dren in the OIT

group had sus-

tained

responsiveness.

Year 4: 50% of the

OIT group

demonstrated

sustained

unresponsiveness

Oral or pharyngeal

adverse events

during 22 ﬁrst

months:

Control: 78%

OIT: 20%

No severe adverse

events occurred.

During years 3 and

4: Mild symp-

toms were pre-

sent in 54.5% of

patients still

dosing.

110 72 egg‐allergic

children

Egg avoidance

diet

Powdered

pasteurized egg

IP: Escalation day

starts with 1 mg

of powder, then

weekly increase

of the dosage

until a dose of

10 g of egg

powder.MP: Diet

including eggs

IP: 10 weeks on average

MP: 12 months

Development of

tolerance

Control: 21.8%

OIT: 92,5%

N/A OIT: 52.5% had

gastrointestinal

symptoms, with

mild (38.1%) to

more severe

(61.9%)

reactions.

14 of 24

LEAU

ET AL.

TABLE 6(Continued)

Ref. Population Control Type of egg Dose Duration Primary outcome

Efﬁcacy of

desensitization

Efﬁcacy of

maintained

tolerance Adverse events

111 31 egg‐allergic

children

Placebo Pasteurized

dehydrated EW

IP: Starting dose of

0.1 mg, weekly

administration of

increasing dose

which are

doubled every

week to reach

4 g in 4 months.

MP: 1 cooked or

boiled egg 3

times a week.

IP: 4 months

MP: 6 months

Egg‐avoidance: 3 months

Achieved

desensitization on

DBPCFC at

4 months.

Desensitization at

4 months:

Control: 0%

OIT: 94%

After 3 months of

withdrawal:

Control: 7.1%

OIT: 31%

Control: No adverse

effects

OIT: 29.4% had

adverse effects.

112 61 egg‐allergic

children

Egg avoidance

diet

IP: Dehydrated EW

MP: Undercooked

egg

IP: Escalation day

starts with

0.08 mg of EW

protein to reach

140 mg. Then,

weekly increase

from 0.02 to

2808 mg.

MP: 1 undercooked

egg every 48h

IP and MP: 3 months

followed by egg

avoidance of

1 month

Induction of sustained

unresponsiveness

(DBPCFC at

4 months with

2808 mg of egg

protein).

OIT: 93% were

desensitized (in a

median of

32 days)

DBPCFC passed at

4 months:

Control: 3%

OIT: 37%

OIT: 70% of patients

had an allergic

reaction during

desensitization

or maintenance

phase.

113 33 egg‐allergic

children

Egg avoidance

diet

IP: Dehydrated EW

MP: Undercooked

egg

IP: Starting with

0.03 mg of EW

protein. Up‐

dosing several

times the same

day after 1 h

without

symptoms. In

case of adverse

events, the

previously

tolerated dose is

ingested as the

ﬁrst dose the

following day.

Target dose of

2808 mg.

MP: Undercooked

egg every 48h

IP: Median of 3 days

(range, 1–14 days)

MP: 5 months

Desensitization to

egg after

5 months of MP

(the ability to eat

1 undercooked

egg without or

mild adverse

events).

Desensitization at

5 months:

Control: 0%

OIT: 89.5%

N/A OIT: Adverse events

occurred in 69%

of patients,

mostly mild or

moderate.

(Continues)

LEAU ET AL.

15 of 24

TABLE 6(Continued)

Ref. Population Control Type of egg Dose Duration Primary outcome

Efﬁcacy of

desensitization

Efﬁcacy of

maintained

tolerance Adverse events

114 36 egg‐allergic

children

Egg avoidance

diet

Dried powdered egg IP: 0.1 mg of powder

increased every

3–4 days to

reach a target

dose of 4 g of

powder.

MP: 4 g of dried

powder egg daily

IP and MP: 6 months Percentage of

patients able to

tolerate 4 g of

powdered egg

without

symptoms in the

OFC at 6 months.

Children who passed

OFC at 6 months

Control: 0%

OIT: 57%

N/A OIT: 94.4% had

allergic

symptoms during

treatment. 1

experienced

anaphylaxis

115 101 egg‐allergic

children

Egg avoidance

diet

Powdered

pasteurized EW

IP:

Starting dose:

0.11 mg of egg

protein

Group PI: 30%

weekly þ5%

daily up‐dosing

Group PII: only

30% weekly

up‐dosing

MP: 3.3 g of EW

protein daily/

every 2 days.

IP: 121.12 91.43 days Total desensitization

at 12 months

Control: 16%

OIT: 84,2%

The PI pattern was

more effective

than the PII

pattern.

N/A 89% patients

developed

adverse events:

Mild (74,53%),

moderate

(21,9%) or

requiring

adrenaline

(3.5%).

116 50 egg allergic

children

tolerant to BE

Egg allergic

children

untolerant

to BE

treated

with OIT

BE: a Mufﬁn or

equivalent

Egg OIT: Pasteurized

raw EW powder

BE: 2 g of EW

protein.

OIT:

IP: 0.1 mg up to

25 mg max of

EW powder on

escalation day,

up‐dosing

every 2 weeks.

MP: Up to 2 g

EW protein

IP: 10 months

MP: 8 weeks at least the

1st year and during

year

Egg avoidance: 8–

10 weeks.

Development of

sustained

unresponsiveness

Year 1:

BE: 7.4%

OIT‐BE tolerant:

56.6%

Year 2:

BE: 14.8%

OIT‐BE tolerant:

78.3%

BE: 11.1%

OIT‐BE tolerant:

43.5%

Similar in the BE

group versus

OIT‐BE tolerant

group.

117 50 children with

moderate to

severe allergic

reaction to

egg.

Egg avoidance

diet for

6 months,

then OIT

IP: Pasteurized raw

EW powder

MP: Raw EW powder

at least 3 times a

week and boiled/

fried egg/foods

containing

IP: Starting dose:

0.1 mg of EW

protein. The dose

was increased

weekly for the

ﬁrst 3 weeks and

then biweekly

IP: 8 months

MP: 3 months

The proportion of

participants

partially

desensitized after

8 months of OIT

(consumption of

any dose below

1 g of EW protein

Control: 4.8% desen-

sitized at

6 months.

OIT:

8 months: 44%

desensitized,

46% partially

desensitized

N/A IP: 82% of the

children

experienced

dosing

symptoms,

mainly mild to

moderate

gastrointestinal

16 of 24

LEAU

ET AL.

TABLE 6(Continued)

Ref. Population Control Type of egg Dose Duration Primary outcome

Efﬁcacy of

desensitization

Efﬁcacy of

maintained

tolerance Adverse events

heated egg on

the remaining

days

MP: 1 g of EW

protein

without

symptoms). 18 months:

72% desensi-

tized, 16%

partially

desensitized.

symptoms. No

severe reactions

were seen.

118 11 egg‐allergic

children

Egg avoidance

diet

Pasteurised liquid

raw EW

IP: Starting with

0.1 mL of EW

protein, with 12

increased levels

to reach the

target dose of

20 mL

MP: 20 mL or 2.66 g

of EW protein

IP: 5 days

MP: 6 months

Tolerance of 40 mL of

EW on OFC

Control: 0%

OIT: 100%

N/A N/A

119 43 egg‐allergic

children

tolerant to BE

Egg‐free baked

products

BE (mufﬁns, biscuits,

cake).

10 g of BE (1.3 g of

egg protein) 2–3

times per week.

No dose

increments.

6 months Raw egg allergy on

OFC 1 month

after ceasing the

intervention.

N/A No signiﬁcant

differences in

raw egg

tolerance.

Control: 33.3% BE:

23.5%

No signiﬁcant differ-

ences in adverse

events between

groups:

Control: 36.3%

BE: 42.8%

Raw hen's egg emulsion or liquid raw EW

120 20 children with

severe egg

allergy

Egg avoidance

diet

Raw hen's egg

emulsion

IP: Starting dose of

0.015 mL of

undiluted

emulsion.

Doubling dose in

hospital 5 times

in 6 months, with

increasing dose

at home based

on the frequency

and severity of

side effects, until

reaching 40 mL.

6 months Tolerance to between

10 and 40 mL of

raw egg emulsion

on OFC

Control: 90% reacted

to the challenge

(with dose

<0.9 mL).

OIT: 90% children

achieved partial

tolerance

N/A All children in OIT

group

experienced

adverse events.

(Continues)

LEAU ET AL.

17 of 24

TABLE 6(Continued)

Ref. Population Control Type of egg Dose Duration Primary outcome

Efﬁcacy of

desensitization

Efﬁcacy of

maintained

tolerance Adverse events

121 20 children with

moderate‐

severe egg

allergy

Egg avoidance

diet

Raw hen's egg

emulsion

IP: Starting dose of

0.27 mg of egg

proteins. Dose

doubled every

8 days until day

80, then doubled

every 16 days to

achieve a total

daily intake of

25 mL of raw egg

in 6 months.MP:

Raw egg or food

containing about

3 eggs 3 times/

week

6 months Daily intake of 25 mL

of raw hen's egg

emulsion

Control: 20%

OIT: 80%

N/A OIT: 50% presented

symptoms

Low allergenic hydrolysed egg

122 29 egg‐allergic

children

Placebo Low allergenic

hydrolysed egg

9 g administered

daily. No dose

increments.

6 months Percentage of

children with a

positive OFC

No signiﬁcative

difference was

observed (36% in

intervention

group and 21%

in controls).

N/A Control: 14% of

adverse events.

Treatment: 46.6% of

adverse events

Abbreviations: BE, baked egg; EW, egg white; IP, induction phase; MP, maintenance phase; N/A, not assessed or not reported; OFC, oral food challenge.

18 of 24

LEAU

ET AL.

to 2 g EW protein daily, no dose increments) and compared this

protocol to an OIT using pasteurized EW powder in baked egg‐

tolerant patients (up dosing to 2 g pasteurized EW protein).

116

In this

study, regular baked egg consumption was less effective to induce

sustained unresponsiveness than the OIT approach with pasteurized

EW powder, with an equivalent safety proﬁle.

116

No randomized

clinical studies have directly compared an OIT using baked or heated

eggs with an OIT using a raw or pasteurized form of egg, although a

randomized non‐controlled study suggested that heated eggs can be

effectively used in OIT.

126

Given the lower allergenicity of heated or

baked egg, it might be hypothesized that the usage of baked or

heated egg might provide a more favourable safety proﬁle, especially

in the initial steps of OIT. In some countries, so‐called food ladders

are now tools used to progressively reintroduce common foods

containing eggs into the diet of egg‐allergic children and to induce

tolerance. These food ladders consist of a step‐wise gradual intro-

duction of increasingly allergenic forms of egg at home, starting from

extensively heated to less heated eggs. These food ladders could be

considered as a form of OIT, but they still lack standardization and a

sound scientiﬁc underpinning of their efﬁcacy.

127,128

Summary:

OIT is an effective approach to promote desensitization

and maintain tolerance in egg‐allergic patients

Dehydrated egg powder is the most commonly tested

form of egg in OIT

The usage of heated or baked forms of egg might be an

option for OIT, but more research is needed to conﬁrm

preliminary studies

CONCLUSION

To understand and establish strategies for the diagnostics, treat-

ment and prevention of food allergy, detailed information about

the responsible allergens is required. In the case of hen's egg

allergy, a part of the patients is reactive to raw but not exten-

sively heated or baked egg. The reasons for this seem to be

FIGURE 3 Overview of the physicochemical characteristics of egg white (EW) proteins and the patient characteristics that are potential

determinants for the tolerance of patients towards heated eggs. The impact of egg heating on primary prevention strategies and oral

immunotherapy is also noted.

LEAU ET AL.

19 of 24

multiple and relate to the physiochemical properties of the heated

egg allergens on the one hand, and patient reactivity on the other

hand (see Figure 3). Heating notably impacts the protein confor-

mation and digestibility of the major EW protein OVA, whereas

heating only impacts OVM upon prolonged heating or when

wheat is present. On the patient side, the overall immunoreac-

tivity towards hen's EW appears to be determinant for the

discrimination of patient tolerant or reactive to heated or baked

egg. Other implicated factors are patient reactivity to the heat‐

stable OVM and to linear versus conformational epitopes, but

these factors require further experimental validation. For primary

prevention strategies of egg allergy, the use of a heated/baked

form of egg might limit adverse reactions when compared to

pasteurized raw egg powder and effectively prevent the egg al-

lergy. A lightly heated or baked form of egg might also be an

interesting option, in order to ensure that an individual is sufﬁ-

ciently exposed to egg epitopes to induce tolerance, but that the

risk of sensitizing or provoke an allergic reaction is low. OIT

seems to be a promising treatment for egg allergy, but signiﬁcant

adverse events have been reported. The use of heated or baked

egg could be an interesting option to limit these adverse events,

but the current literature is insufﬁcient to conclude the efﬁcacity

of such an approach. Taken together, a good understanding of the

impact of food transformation on its allergenicity might be helpful

to ameliorate primary prevention and treatment strategies for

food allergies.

AUTHOR CONTRIBUTIONS

Audrey Leau: Conceptualization (supporting); formal analysis (equal);

investigation (equal); writing—original draft (supporting). Sandra

Denery‐Papini: Conceptualization (supporting); supervision (sup-

porting); validation (supporting); writing—review and editing (sup-

porting). Marie Bodinier: Conceptualization (supporting); supervision

(supporting); validation (supporting); writing—review and editing

(supporting). Wieneke Dijk: Conceptualization (lead); formal analysis

(equal); funding acquisition (lead); investigation (equal); resources

(lead); supervision (lead); visualization (lead); writing—original draft

(lead).

ACKNOWLEDGEMENTS

This work was supported by INRAE (ORIA grant, to W.D.) and the

Pays de la Loire region (PULSAR grant, to W.D.).

CONFLICT OF INTEREST STATEMENT

All authors declare that they have no conﬂicts of interest.

DATA AVAILABILITY STATEMENT

Data sharing is not applicable to this article as no new data were

created or analysed in this study.

ORCID

Wieneke Dijk

https://orcid.org/0000-0003-1676-7751

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How to cite this article: Leau A, Denery‐Papini S, Bodinier M,

Dijk W. Tolerance to heated egg in egg allergy: explanations

and implications for prevention and treatment. Clin Transl

Allergy. 2023;e12312. https://doi.org/10.1002/clt2.12312

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Prevalence estimates of eight big food allergies in Europe: Updated systematic review and meta‐analysis

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Full-text available

Jul 2023
ALLERGY

In 2014, the European Academy of Allergy and Clinical Immunology published prevalence estimates for food allergy (FA) and food sensitization (FS) to the so‐called eight big food allergens (i.e. cow's milk, egg, wheat, soy, peanut, tree nuts, fish and shellfish) in Europe for studies published between 2000 and 2012. The current work provides 10‐year updated prevalence estimates for these food allergens. A protocol was registered on PROSPERO before starting the research (reference number CRD42021266657). Six databases were searched for studies published 2012–2021, added to studies published up to 2012, resulting in a total of 93 studies. Most studies were graded as at moderate risk of bias. The overall pooled estimates for all age groups of self‐reported lifetime prevalence were as follows: cow's milk (5.7%, 95% confidence interval 4.4–6.9), egg (2.4%, 1.8–3.0), wheat (1.6%, 0.9–2.3), soy (0.5%, 0.3–0.7), peanut (1.5%, 1.0–2.1), tree nuts (0.9%, 0.6–1.2), fish (1.4%, 0.8–2.0) and shellfish (0.4%, 0.3–0.6). The point prevalence of food challenge‐verified allergy were as follows: cow's milk (0.3%, 0.1–0.5), egg (0.8%, 0.5–1.2), wheat (0.1%, 0.01–0.2), soy (0.3%, 0.1–0.4), peanut (0.1%, 0.0–0.2), tree nuts (0.04%, 0.02–0.1), fish (0.02%, 0.0–0.1) and shellfish (0.1%, 0.0–0.2). With some exceptions, the prevalence of allergy to common foods did not substantially change during the last decade; variations by European regions were observed.

Frequency of food allergy in Europe: An updated systematic review and meta‐analysis

Article

Full-text available

Nov 2022
ALLERGY

Food allergy (FA) is increasingly reported in Europe, however, the latest prevalence estimates were based on studies published a decade ago. The present work provides the most updated estimates of the prevalence and trends of FA in Europe. Databases were searched for studies published between 2012 and 2021, added to studies published up to 2012. In total, 110 studies were included in this update. Most studies were graded as moderate risk of bias. Pooled lifetime and point prevalence of self‐reported FA were 19.9% (95% CI 16.6–23.3) and 13.1% (95% CI 11.3–14.8), respectively. The point prevalence of sensitization based on specific IgE (slgE) was 16.6% (95% CI 12.3–20.8), skin prick test (SPT) 5.7% (95% CI 3.9–7.4), and positive food challenge 0.8% (95% CI 0.5–0.9). While lifetime prevalence of self‐reported FA and food challenge positivity only slightly changed, the point prevalence of self‐reported FA, sIgE and SPT positivity increased from previous estimates. This may reflect a real increase, increased awareness, increased number of foods assessed, or increased number of studies from countries with less data in the first review. Future studies require rigorous designs and implementation of standardized methodology in diagnosing FA, including use of double‐blinded placebo‐controlled food challenge to minimize potential biases.

PrEggNut Study: protocol for a randomised controlled trial investigating the effect of a maternal diet rich in eggs and peanuts from

Article

Full-text available

Jun 2022

Introduction Clinical studies supported by immunological data indicate early life intervention strategies to be promising in reducing the growing global burden of food allergies. The events that predispose to food allergy, including the induction of allergen-specific immune responses, appear to be initiated early in development. Early exposure to food allergens in utero and via breast milk is likely to be important in initiating oral tolerance. We aim to determine the effectiveness of higher maternal food allergen consumption during pregnancy and lactation on infant food allergy outcomes. Methods and analysis This is a multisite, parallel, two-arm (1:1 allocation), single-blinded (outcome assessors, statistical analyst and investigators), randomised controlled trial. Pregnant women (<23 weeks’ gestation) whose (unborn) infants have at least two biological family members (mother, father or siblings) with medically diagnosed allergic disease are eligible to participate. After obtaining written informed consent, pregnant women are randomised to either a high egg and peanut diet (at least 6 eggs and 60 peanuts per week) or standard (low) egg and peanut diet (no more than 3 eggs and 30 peanuts per week). The women are asked to follow their allocated diet from <23 weeks’ gestation to 4 months’ lactation. The primary outcome is food challenge proven IgE-mediated egg and/or peanut allergy in the infants at 12 months of age. Key secondary outcomes include infant sensitisation to egg and/or peanut and infant eczema. Our target sample size is 2136 women. Analyses will be performed on an intention-to-treat basis according to a pre-specified statistical analysis plan. Ethics and dissemination Ethical approval has been granted from the Women’s and Children’s Health Network Human Research Ethics Committee (approval number HREC/18/WCHN/42). Trial results will be presented at scientific conferences and published in peer-reviewed journals. Trial registration number Australian New Zealand Clinical Trials Registry ACTRN12618000937213.

Cow's milk and egg protein threshold dose distributions in children tolerant to beef, baked milk, and baked egg

Article

Full-text available

Jun 2022
ALLERGY

Background The use of eliciting doses (EDs) for food allergens is necessary to inform individual dietary advice and food allergen risk‐management. The Eliciting Dose 01 (ED01) for milk and egg, calculated from populations of allergic subjects undergoing oral food challenges (OFCs), are 0.2 mg total protein. The respective Eliciting Dose 05 (ED05) is 2.4 mg for milk and 2.3 mg for egg. As about 70% children allergic to such foods may tolerate them when baked, we sought to verify the EDs of that subpopulation of milk and egg‐allergic children. Methods We retrospectively assessed consecutive OFC for fresh milk and egg between January 2018 and December 2020 in a population of baked food‐tolerant children. Results Among 288 children (median age 56 ‐ IQR 36–92.5 months, 67.1% male) included, 87 (30.2%) returned positive OFC results, 38 with milk and 49 with egg. The most conservative ED01 was 0.3 mg total protein (IQR 0.03–2.9) for milk and 14.4 mg total protein (IQR 3.6–56.9) for egg. The respective ED05 was 4.2 (IQR 0.9–19.6) mg for milk and 87.7 (IQR 43–179) mg for egg. Such thresholds are, respectively, 1.5 (milk ED01), 1.75 (milk ED05), 72 (egg ED01), and 38.35 (egg ED05) times higher than the currently used thresholds. Conclusions The subpopulation of children allergic to milk and egg, but tolerant to baked proteins, displays higher reactivity thresholds than the general population of children allergic to milk and egg. Their risk stratification, in both individual and population terms, should consider this difference. In baked milk‐tolerant children, milk causes reactions at lower doses than egg in our group of egg‐tolerant children. This could be associated with the relative harmlessness of egg compared with milk in the determinism of fatal anaphylactic reactions in children.

S3 Guideline Allergy Prevention

Article

Full-text available

Mar 2022

Background: The persistently high prevalence of allergic diseases in Western industrial nations and the limited possibilities of causal therapy make evidence-based recommendations for primary prevention necessary. Methods: The recommendations of the S3 guideline Allergy Prevention, published in its last version in 2014, were revised and consulted on the basis of a current systematic literature search. The evidence search was conducted for the period 06/2013 - 11/2020 in the electronic databases Cochrane and MEDLINE, as well as in the reference lists of current reviews and through references from experts. The literature found was screened in two filtering processes, first by title and abstract, and the remaining papers were screened in the full text for relevance. The studies included after this were sorted by level of evidence, and the study quality was indicated in terms of potential bias (low/high). The revised recommendations were formally agreed and consented upon with the participation of representatives of the relevant professional societies and (self-help) organizations (nominal group process). Of 5,681 hits, 286 studies were included and assessed. Results: Recommendations on maternal nutrition during pregnancy and breastfeeding as well as on infant nutrition in the first months of life again play an important role in the updated guideline: Many of the previous recommendations were confirmed by the current data. It was specified that breastfeeding should be exclusive for the first 4 - 6 months after birth, if possible, and that breastfeeding should continue with the introduction of complementary foods. A new recommendation is that supplementary feeding of cow's milk-based formula should be avoided in the first days of life if the mother wishes to breastfeed. Furthermore, it was determined that the evidence for a clear recommendation for hydrolyzed infant formula in non-breastfed infants at risk is currently no longer sufficient. It is therefore currently recommended to check whether an infant formula with proven efficacy in allergy prevention studies is available until the introduction of complementary feeding. Finally, based on the EAACI guideline, recommendations were made for the prevention of chicken egg allergy by introducing and regularly giving thoroughly heated (e.g., baked or hard-boiled) but not "raw" chicken egg (also no scrambled egg) with the complementary food. The recommendation to introduce peanut in complementary feeding was formulated cautiously for the German-speaking countries: In families who usually consume peanut, the regular administration of peanut-containing foods in age-appropriate form (e.g., peanut butter) with the complementary diet can be considered for the primary prevention of peanut allergy in infants with atopic dermatitis (AD). Before introduction, a clinically relevant peanut allergy must be ruled out, especially in infants with moderate to severe AD. There is still insufficient evidence for an allergy-preventive efficacy of prebiotics or probiotics, vitamin D, or other vitamins in the form of supplements so that recommendations against their supplementation were adopted for the first time in the current guideline. Biodiversity plays an important role in the development of immunological tolerance to environmental and food allergens: there is clear evidence that growing up on a farm is associated with a lower risk of developing asthma and allergic diseases. This is associated with early non-specific immune stimulation due to, among other things, the greater microbial biodiversity of house dust in this habitat. This aspect is also reflected in the recommendations on animal husbandry, on which a differentiated statement was made: In families without a recognizable increased allergy risk, pet keeping with cats or dogs should not generally be restricted. Families with an increased allergy risk or with children with already existing AD should not acquire a new cat - in contrast, however, dog ownership should not be discouraged. Interventions to reduce exposure to dust mite allergens in the home, such as the use of mite allergen-proof mattress covers ("encasings"), should be restricted to patients with already proven specific sensitization against house dust mite allergen. Children born by caesarean section have a slightly increased risk of asthma - this should be taken into account when advising on mode of delivery outside of emergency situations. Recent work also supports the recommendations on air pollutants: Active and passive exposure to tobacco smoke increase the risk of allergies, especially asthma, and should therefore be avoided. Exposure to nitrogen oxides, ozone, and small particles (PM 2.5) is associated with an increased risk, especially for asthma. Therefore, exposure to emissions of nitrogen oxides, ozone, and small particles (PM 2.5) should be kept low. The authors of this guideline are unanimously in favor of enacting appropriate regulations to minimize these air pollutants. There is no evidence that vaccinations increase the risk of allergies, but conversely there is evidence that vaccinations can reduce the risk of allergies. All children, including children at risk, should be vaccinated according to the current recommendations of the national public health institutes, also for reasons of allergy prevention. Conclusion: The consensus of recommendations in this guideline is based on an extensive evidence base. The update of the guideline enables evidence-based and up-to-date recommendations for the prevention of allergic diseases including asthma and atopic dermatitis.

Food allergen ladders: A need for standardization

Article

Full-text available

Dec 2021
PEDIATR ALLERGY IMMU

Introduction The process of gradually reintroducing food allergens into an individual's diet is referred to as food allergen “ladders”. There remain many questions regarding the foods chosen, structure and composition of the ladder, and medical and safety considerations. The COVID‐19 pandemic has propelled us into an era where medicine is increasingly practiced via online platforms, highlighting the need for standardized food allergen ladder approaches for successful and safe introduction of food allergens. Methods We performed a search of currently published food allergen ladders and obtained published information and clinical expertise to summarize current knowledge and suggest future standardized approaches for using food allergen ladders. Results There are currently a limited number of published milk, egg, wheat, and soy ladders. We suggest the following points should be considered when developing food ladders: (1) Food allergen: dose, time, and temperature of heating of the food allergen, simplicity of the ladder and recipes, the possible role of the wheat matrix, and testing for allergenic protein levels to standardize doses; (2) Nutritional factors: health and nutritional value of the foods in the ladder, taste, texture, and cultural appropriateness of foods should be considered; and (3) Medical aspects: consideration of which patients are safe to undergo ladders outside of the clinical setting, other safety aspects and risk factors for severe reactions, number of days suggested per steps, and availability and provision of rescue medication. Written instructions and recipes should be provided to families who wish to use food allergen ladders. Discussion Food allergen ladders used for gradual reintroduction of food allergens into a food allergic individual's diet are increasingly being used internationally. Standardization regarding the foods included in the ladder and medical considerations are required to practice patient‐centered care, best assist patients and families, and ensure safety.

Efficacy and safety of low- and high-dose slow oral egg immunotherapy for hen's egg allergy: Single-center non-inferiority randomized trial

Article

Apr 2023

Background: Low-dose oral immunotherapy (OIT) is a safe treatment for hen's egg allergy; however, comparison of its therapeutic effects with those of high-dose OIT has not been reported. Objective: To compare the efficacy of low- and high-dose boiled egg-white (EW) OIT for hen's egg allergy. Methods: Patients with hen's egg allergy were randomly assigned to two groups: OIT using hard-boiled EW with a maximum maintenance dose of 2 and 20 g in the low-dose (L-D) and high-dose (H-D) groups, respectively. The intake dose was ingested twice a week, increased by approximately 20% per week until reaching the target maintenance dose (2 or 20 g hard-boiled EW), and maintained thereafter according to the schedule. The threshold was confirmed via oral food challenge (OFC) after 6 months, and the difference in the proportion of subjects passing the exit OFC between groups was evaluated. Results: Fifty-two patients (L-D, n = 23; H-D, n = 29) were enrolled. Thirty-three patients (L-D, n = 17; H-D, n = 16) completed the 6-month OIT and underwent an exit OFC. In total, three (L-D, 3/17; H-D, 3/16) patients in each group tested negative for an exit OFC with a 20-g reactive dose (p = 1.000). EW-specific IgE levels in both groups decreased significantly after OIT (L-D, p < 0.001; H-D, p = 0.002). Conclusions: A threshold-elevating effect was observed in the L-D group, not inferior to that in the H-D group. Low-dose OIT may be appropriate to treat hen's egg allergy for the first 6 months.

High-resolution mass spectrometry unveils the molecular changes of ovalbumin induced by heating and their influence on IgE binding capacity

Article

Jul 2022
FOOD CHEM

Ovalbumin (OVA) is a food allergen whose allergenicity is modulated by heating. We aimed to establish a molecular connection between heat-induced modifications and the modulation of the IgE binding capacity of OVA. For this, we used model samples of heat-modified OVA with increasing complexity; glycated, aggregated or glycated and aggregated. Using sera from egg-allergic individuals, we show that both aggregation and glycation strongly impacted IgE binding capacity, despite limited structural changes for glycated OVA. A molecular exploration at the amino acid level using high-resolution mass spectrometry = revealed extensive cross-linking, mostly through disulfide and dehydroprotein bridges, and moderate but significant glycation. Structural modifications affected residues located within or at a few amino acids distance of known human linear IgE epitopes, such as C121, K123, S169, K190, K207, H332 and C368. We thus unveil key amino residues implicated in the changes in IgE binding of OVA induced by heating.

Deciphering Changes in the Structure and IgE-Binding Ability of Ovalbumin Glycated by α-Dicarbonyl Compounds under Simulated Heating

Article

Jan 2022
J AGR FOOD CHEM

Mapping Sequential IgE-Binding Epitopes on Major and Minor Egg Allergens

Article

Nov 2021

Introduction: Molecular studies of hen's egg allergens help define allergic phenotypes, with IgE to sequential (linear) epitopes on the ovomucoid (OVM) protein associated with a persistent disease. Epitope profiles of other egg allergens are largely unknown. The objective of this study was to construct an epitope library spanning across 7 allergens and further evaluate sequential epitope-specific (ses-)IgE and ses-IgG4 among baked-egg reactive or tolerant children. Methods: A Bead-Based Epitope Assay was used to identify informative IgE epitopes from 15-mer overlapping peptides covering the entire OVM and ovalbumin (OVA) proteins in 38 egg allergic children. An amalgamation of 12 B-cell epitope prediction tools was developed using experimentally identified epitopes. This ensemble was used to predict epitopes from ovotransferrin, lysozyme, serum albumin, vitellogenin-II fragment, and vitellogenin-1 precursor. Ses-IgE and ses-IgG4 repertoires of 135 egg allergic children (82 reactive to baked-egg, the remaining 52 tolerant), 46 atopic controls, and 11 healthy subjects were compared. Results: 183 peptides from OVM and OVA were screened and used to create an aggregate algorithm, improving predictions of 12 individual tools. A final library of 65 sequential epitopes from 7 proteins was constructed. Egg allergic children had higher ses-IgE and lower ses-IgG4 to predominantly OVM epitopes than both atopic and healthy controls. Baked-egg reactive children had similar ses-IgG4 but greater ses-IgE than tolerant group. A combination of OVA-sIgE with ses-IgEs to OVM-023 and OVA-028 was the best predictor of reactive phenotype. Conclusion: We have created a comprehensive epitope library and showed that ses-IgE is a potential biomarker of baked-egg reactivity.

Tolerance to heated egg in egg allergy: Explanations and implications for prevention and treatment

Abstract

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