Does Bedding Affect the Airway and Allergy?

Abstract

Various cross-sectional and longitudinal studies have suggested that synthetic bedding is associated with asthma, allergic rhinitis and eczema while feather bedding seems to be protective. Synthetic bedding items have higher house dust mite allergen levels than feather bedding items. This is possibly the mechanism involved although fungal and bacterial proinflammatory compounds and volatile organic compounds may play a role. In this review we present and discuss the epidemiological evidence and suggest possible mechanisms. Primary intervention studies are required to show whether feather bedding is protective for the development of childhood asthma and allergic diseases while secondary intervention studies are required to potentially reduce symptoms and medication use in subjects with established disease.

Full text

65www.theijoem.com Vol 2 Number 2; April, 2011
Review
Correspondence to
Rob Siebers, Associate
Professor, Wellington
Asthma Research
Group, Department of
Medicine, School of
Medicine and Health
Sciences, University of
Otago, PO Box 7343,
Wellington 6242, New
Zealand.
Tel: +64-4-918-6838
Fax: +64-4-389-5427
E-mail: rob.siebers@
otago.ac.nz
Abstract
Various cross-sectional and longitudinal studies have suggested that synthetic bedding is
associated with asthma, allergic rhinitis and eczema while feather bedding seems to be
protective. Synthetic bedding items have higher house dust mite allergen levels than feather
bedding items. This is possibly the mechanism involved although fungal and bacterial pro-
inammatory compounds and volatile organic compounds may play a role. In this review we
present and discuss the epidemiological evidence and suggest possible mechanisms. Pri-
mary intervention studies are required to show whether feather bedding is protective for the
development of childhood asthma and allergic diseases while secondary intervention studies
are required to potentially reduce symptoms and medication use in subjects with established
disease.
Keywords: Asthma; Allergy; House dust mite; Fungi; Volatile organic compounds; Bed-
ding; Synthetic; Feather
RW Siebers, J Crane
Does Bedding Affect the
Airway and Allergy?
Wellington Asthma Re-
search Group, School
of Medicine and Health
Sciences, University of
Otago, Wellington, New
Zealand
Introduction
The International Study of Asthma
and Allergies in Childhood (ISAAC)
has been instrumental in determin-
ing the global prevalence and the severity
of asthma symptoms in 6–7-year-old and
13–14-year-old children. The first major
findings from the ISAAC studies showed a
20- to 60-fold difference between 155 cen-
tres in 56 countries in the prevalence of
asthma symptoms and allergic diseases.1
The latest results from Phase III of ISAAC,
with a greater number of children, centres
and countries than those of ISAAC Phase
I, again showed a wide variation in asth-
ma symptoms worldwide. For instance,
prevalence rates of 12-month wheeze
in 13–14-year-old children ranged from
0.8% in Tibet, China to 32.6% in Welling-
ton, New Zealand.2
The causative factors for asthma are
multi-factorial, but it is increasingly be-
ing recognized that, in addition to genetic
susceptibility, the indoor environment is
an important factor. The bedroom envi-
ronment may play an important role given
that we spend about one-third of our time
in the bed with our airways close to pil-
lows, mattresses and duvets (also known
as quilts or comforters) that are signifi-
cant reservoirs of allergens, fungi and bac-
teria. In the last 15 years, epidemiological
studies have suggested that synthetic bed-
ding is associated with an increased risk
of asthma while feather bedding is asso-
ciated with protection. In this article, we
review the epidemiological evidence and
suggest potential mechanisms for these
associations.
Bedding and Severe Asthma
A questionnaire-based case-control study
showed that the use of synthetic pillows
was the only indoor environmental fac-

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66
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Asthma, Allergy and Bedding Exposure
tor significantly associated with severe
wheeze in school-age children.3 Indepen-
dent associations with severe wheeze (12
or more wheezing attacks or a speech lim-
iting attack of wheeze in the preceding 12
months) and the use of synthetic pillows
were seen with an odds ratio (OR) of 2.78
(95% CI: 1.89–4.17). Interestingly, the use
of feather pillows was associated with less
severe wheeze (OR: 0.36; 95% CI: 0.24–
0.53) and remained highly significant even
after restricting the analysis to children
without a family history of atopy or whose
parents did not make any changes in
the bedroom. Since then, a number of
cross-sectional studies have described
associations of asthma symptoms and
allergic diseases with synthetic bedding
or an apparent protective effect of feather
bedding.
Bedding, Asthma and Allergic
Diseases
Butland, et al, reported an increased
prevalence of wheezing of 16% in 8-year-
old London school children between 1978
and 1991.4 The authors obtained detailed
indoor environmental data, including the
type of pillow used by the child. Their
main finding was that an increased use of
non-feather pillows over the 13-year time
period (44% in 1978 and 67% in 1991) was
the only indoor environmental exposure
studied which was associated with the in-
crease in wheezing prevalence over this
time period, even when taking into ac-
count possible changes in pillow type due
to asthma symptoms.
In a study on the prevalence of asthma
and allergic diseases in children from
East and West Germany, Duhme, et al,
found that the use of feather bedding by
5–8-year-old children was associated with
a reduced prevalence of asthma symptoms,
allergic rhinitis and eczema in both East
and West Germany.5 Adjusted for parental
atopy and allergen avoidance practices,
odds ratios for asthma, rhinitis and eczema
were 0.48 (95% CI: 0.35–0.66), 0.53 (95%
CI: 0.37–0.76) and 0.63 (95% CI: 0.47–
0.85), respectively in East Germany and
0.39 (95% CI: 0.31–0.50), 0.58 (95% CI:
0.43–0.77) and 0.64 (95% CI: 0.49–0.83),
respectively in West Germany.
In a small case-control study of under
2-year-old infants, recurrent wheezing
was significantly associated with the use of
synthetic mattresses, quilts and pillows.6
However, wheezing in very young infants
is most likely due to viral respiratory
infections. Furthermore, the authors
did not adjust for potential confounding
factors such as a family history of atopy and
environmental tobacco smoke exposure,
both of which were also associated with
recurrent wheezing in that study.
In two separate publications,7,8 Zacha-
rasiewicz, et al, reported that wheezing in
the last 12 months and symptoms strongly
suggestive of atopic rhinitis were signifi-
cantly associated with the use of synthetic
bedding with adjusted odds ratios (aOR)
of 1.33 (95% CI: 1.18–1.49) and 1.21 (95%
CI: 1.09–1.36), respectively. This was a
very large study of 6–9-year old children
in Austria where about 35 000 took part in
the asthma symptoms study7 while a sub-
set of about 18 000 who excluded reported
allergen avoidance took part in the allergic
rhinitis study.8
Frosh, et al, conducted a question-
naire-based cross-sectional study of
about 2500 friends and relatives accom-
panying patients attending outpatients
departments at one London hospital to
determine whether ownership of furred
animals or the use of non-feather pillows
was associated with seasonal or perennial
rhinitis.9 After excluding subjects who had
changed their pillow because of allergies,
non-feather pillow use was significantly
associated with both perennial rhinitis
(aOR: 2.41; 95% CI: 1.32–4.39) and non-

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R. W. Siebers, J. Crane
significantly with seasonal rhinitis (aOR:
1.33; 95% CI: 0.93–1.91).
Yemaneburhan, et al, determined the
prevalence of wheeze and asthma in urban
and rural Ethiopia and assessed whether
etiological factors were associated with
urban/rural differences.10 Among studied
etiological factors was the use of synthetic
mattresses and pillows. They found that
synthetic foam mattresses and pillows
were associated with wheeze of 12 months
duration (aOR: 1.48; 95% CI: 1.14–1.91
and 1.40; 95% CI: 1.07–1.84, respectively).
Furthermore, the use of synthetic foam
mattresses and pillows were also associated
with sensitization to the house dust mite
Dermatophagoides pteronyssinus (aOR:
1.97; 95% CI: 1.16–3.33 and 2.09; 95% CI:
1.22–3.57, respectively).
In a nested case-control study, McNally,
et al, looked at the association between
atopic eczema and a number of indoor
environmental factors in primary school
children in the UK.11 Among factors
studied were the use of synthetic pillows
and duvets which was used by 85% and
91%, respectively. Synthetic pillow use
was significantly associated with a 1-year
period of atopic eczema symptoms (aOR:
1.51; 95% CI: 1.01–2.28) with a population
attributable risk (PAR) of 28%. This
association remained significant for
lifetime atopic eczema symptoms (aOR:
1.50; 95% CI: 1.07–2.11; PAR: 27%). The
PAR is a measure of the proportion of cases
in the population that can be attributed to
the exposure. Synthetic duvet use was also,
but non-significantly, associated with
an increased risk of atopic eczema (aOR:
1.33; 95% CI: 0.82–2.14 and 1.43; 95% CI:
0.98–2.13, respectively for a 1-year period
and lifetime atopic eczema).
An Australian cross-sectional study
found that synthetic duvet use was
significantly associated with asthma, recent
wheeze and allergic rhinoconjunctivitis
in atopic children but not in non-atopic
children.12 When restricting the analysis
to children who were sensitized to house
dust mites, the association strengthened.
But children who were sensitized to other
allergens than house dust mites showed
no association between synthetic duvets
and allergic diseases. Synthetic duvet use
was also associated with increased past
hospital attendance for asthma and with
more frequent rather than infrequent
wheezing. The authors postulated that the
association between synthetic bedding
use and adverse respiratory outcomes was
most likely related to the higher allergen
content of synthetic bedding. This aspect
will be explored further in this review.
Ponsonby, et al, examined the relation
between feather quilt use and respiratory
parameters and atopic sensitization
to allergens of the house dust mites
D. pteronyssinus and D. farinea.13
Feather quilt and feather pillow use was
significantly associated with reduced
house dust mite sensitization (aRR: 0.60;
95% CI: 0.45–0.80 and aRR: 0.39; 95%
CI: 0.16–0.99, respectively). Sensitized
children who slept under feather quilts
had smaller weal sizes compared to
sensitized children sleeping under other
quilt types. Furthermore, feather quilt
use was significantly associated with
reduced frequent wheeze, defined as
>12 wheeze episodes in preceding 12
months (aRR: 0.24; 95% CI: 0.07–0.86)
and this was more evident among house
dust mite sensitized children. Children
who slept under feather quilts used less
inhaled steroid medication and had
reduced hospital attendance for asthma
in the preceding 12 months. All the above
protective effects of feather bedding were
not affected by a family history of asthma
or by allergen avoidance measures.
In a cross-sectional study from
Tasmania, Australia, synthetic bedding use
by children was significantly associated
with frequent wheeze, night wheeze and a
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history of asthma ever.14 Among children
with asthma, synthetic bedding use was
significantly associated with increased
asthma medication use.
Having demonstrated that synthetic
bedding use was associated with increased
wheeze in their previous studies,12-14
Ponsonby, et al, then examined whether
these adverse effects of synthetic bedding
differed by the child’s usual sleep position.15
Synthetic quilt use was significantly
associated with frequent wheeze among
children who slept in the supine position
(aOR: 2.37; 95% CI: 1.08–5.23) but not in
the non-supine position (aOR: 1.06; 95%
CI: 0.60–1.88). Also, the supine sleeping
group using synthetic quilts had lower
post-exercise forced expiratory volume
in 1 second measures (FEV1). The authors
concluded that in the supine sleeping
position the child’s airways are in closer
proximity to the higher allergen content of
synthetic bedding leading to an increase
in asthma symptoms.
A few studies conducted in other
countries have also shown associations
between bedding type and asthma
symptoms or allergic sensitization. In
Norway, use of synthetic pillows and
comforters was associated with severe
asthma.16 In Belgium use of non-synthetic
bedding material was significantly
associated with a reduced risk of atopic
sensitization (at least one positive skin
prick test to seven inhalant allergens) with
an OR of 0.67 and was also associated with
fewer reported episodes of wheezing.17 In
Hungary, the prevalence of allergic rhinitis
in 6–12-year-old school children was
reported as being significantly associated
with the use of feather bedding (aOR:
0.753; 95% CI: 0.641–0.884).18 However,
it was subsequently pointed out that the
authors misinterpreted their results and
that feather bedding use appeared to
be protective for allergic rhinitis in that
study.19 In Croatia, use of feather pillows
was associated with reduced symptoms
of allergic disease (wheezing and/or
allergic rhinoconjunctivitis and/or atopic
eczema).20
Therefore, many studies have shown
that synthetic bedding is associated
with asthma or allergic diseases or that
feather bedding seems to be protective;
however, two studies have not. Bisgaard,
et al, found no association with feather
pillow use and early childhood eczema
at age three years in a prospective birth
cohort study from Denmark.21 Behrens,
et al, argue that most studies looking at
bedding type use and its association with
asthma and allergic diseases did not fully
account for potential changes in bedding
by patients.22 In their study, Behrens, et
al, analyzed data from their ISAAC Phase
III cross-sectional survey.23 In preliminary
analyses synthetic bedding (pillows and
blankets) were highly associated with a
high number of wheezing attacks with
adjusted prevalence ratios (aPR) of 4.44
(95% CI: 2.84–6.94) and 3.80 (95% CI:
TAKE-HOME MESSAGE
●Epidemiological studies have predomi-
nantly shown that synthetic bedding is
associated with asthma and allergic
diseases while feather bedding ap-
pears to be protective.
●The much higher house dust mite al-
lergen load of synthetic bedding has
been postulated as the putative mech-
anism although fungal and bacte-
rial pro-inflammatory compounds and
volatile organic compounds may play
a role.
●Well-designed primary and secondary
intervention studies are required to de-
termine whether feather bedding can
reduce the burden of asthma and al-
lergic diseases.
Asthma, Allergy and Bedding Exposure

www.theijoem.com Vol 2 Number 2; April, 2011 69
2.48–5.82), respectively for synthetic
pillows and blankets. When they restricted
the analysis by excluding subjects who
had changed their bedding type due to
existing atopic disease or family history
of atopy, the positive associations of
synthetic bedding with wheezing attacks
disappeared. Their results are surprising
as the study was a subset of an earlier
study where they found significant inverse
relations between feather bedding use and
wheezing and allergic diseases, adjusted
for parental atopy and allergen avoidance
practices.5
Prospective Studies
Cross-sectional and case-control studies
focus on current exposure and outcomes
and are vulnerable to selection and infor-
mation bias. Thus, parents may choose
particular types of bedding due to the
child’s disease status or family history of
atopy. Alternatively, the child’s atopic sta-
tus may influence past exposure reporting
information. Prospective studies reduce
selection bias and eliminate information
bias. To date, three full published stud-
ies and one study published as an abstract
have reported on bedding type use from
birth and development of asthma and al-
lergic diseases in infancy.
Nafstad, et al, were the first to show
that the use of a feather quilt from birth
seemed to be protective for developing
bronchial obstruction at age two years
and asthma and allergic rhinitis at age
four years.24 In their cohort study, the
authors collected information on the type
of duvet the infant was exposed to at 6,
12 and 24 months. Bronchial obstruction
at age two years was defined as at least
three out of five symptoms or signs (i.e.,
wheezing, chest recession, rhonchi during
auscultation, forced expiration, and
rapid breathing), one of which had to be
physician diagnosed. Asthma and allergic
rhinitis at age four years was physician
diagnosed. Use of feather duvets at age
six months was inversely associated with
bronchial obstruction at age two years
(aOR: 0.59; 95% CI: 0.41–0.86) and
physician-diagnosed asthma at age four
years (0.38; 95% CI: 0.23–0.64). There
seemed to be (non-significant) protective
trends of feather duvet use at age six
months and allergic rhinitis at age four
years (aOR: 0.73; 95% CI: 0.43–1.18). The
authors concluded that their results do not
support advice against the use of feather
bedding by asthmatics.
In Australia, another type of infant
bedding relatively popular is the cocoon
or baby nest. This is a synthetic material
padded sleeping bag with a hood which is
normally placed on a flat surface or pram
or basinet with the infant inside. Trevillian,
et al, found that cocoon use in infancy
was associated with an increased risk of
recent wheeze (aOR: 4.33; 95% CI: 2.08–
9.02) and night time wheeze (aOR: 3.35;
95% CI: 1.52–7.39) at age seven years.25
Adjustments for family history, maternal
smoking and child’s history of asthma did
not alter the associations, neither were
parents of infants with a family history
of asthma selectively using cocoons. If
infants were also exposed to synthetic
quilts or pillows in infancy, the association
between cocoon use and recent wheeze
increased (aOR: 4.33; 95% CI: 2.08–9.02).
The Tasmanian (Australia) infant
cohort was further studied to investigate
the role of composite bedding environment
at birth on the development of asthma at
age seven years.26 The composite bedding
groups were 1) no synthetic bedding or
sheepskins; 2) only one synthetic bedding
item or sheepskin only or one synthetic
bedding item plus sheepskin; and 3) two
or more synthetic bedding items with or
without sheepskins. The authors found
that composite bedding was associated
with one or more wheezing episodes in
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the last 12 months (at age seven years) and
that this association was strengthened
with increasing synthetic bedding items.
Furthermore, bedroom heating, recent
painting of the bedroom and absence of
bedroom carpeting increased these effects.
Thus, increasing exposure to synthetic
bedding in infancy increased wheezing
episodes in childhood and was enhanced
by certain home environmental conditions.
In a New Zealand infant cohort study
we investigated whether use of feather
pillows and duvets at age two years was
associated with an altered risk of wheeze
and asthma at age four years.27 At age
two years only 25 out of 524 infants slept
with feather pillows and 57 out of 581
infants slept with feather duvets. aOR’s
for feather pillow use with wheeze at age
four years was 0.09 (95% CI: 0.01–0.67)
and for doctor diagnosed asthma was 0.18
(95% CI: 0.02–1.36). Comparative aOR’s
for feather duvet use were 0.32 (95% CI:
0.14–0.72) and 0.52 (95% CI: 0.22–1.17),
respectively for wheeze and asthma at age
four years. Therefore, feather bedding use
early in infancy appeared to be protective
for development of wheeze in childhood
and there appeared to be a protective trend
for asthma development in childhood.
Mechanisms
Allergens
A number of cross-sectional and longitudi-
nal studies have shown that synthetic bed-
ding may contribute to asthma and aller-
gic diseases while feather bedding seems
to be protective. So what are the potential
mechanisms for these effects? Strachan
and Carey postulated that the three-fold
increased risk of severe wheezing in school
children associated with the use of syn-
thetic pillows might be due to the release
of volatile organic compounds (VOCs)
from synthetic pillows, thus, increasing
mucosal permeability to allergens.3 We
hypothesized that synthetic pillows might
also have a larger allergen load compared
to feather pillows. Therefore, we showed
that synthetic pillows had about eight-fold
higher levels of the house dust mite aller-
gen, Der p 1, than feather pillows.28 Our
findings were confirmed in the UK where
allergen levels are about 20-fold lower
than in New Zealand.29 The UK authors
subsequently demonstrated that synthetic
pillows contained about 7- to 8-fold higher
levels of cat and dog allergens, compared
to feather pillows.30 We subsequently
studied how quickly new allergen-free pil-
lows accumulate house dust mite allergen.
Over a 12-month period, synthetic pillows
accumulated Der p 1 at a higher level than
feather pillows and accumulation on both
types of pillow was strongly governed by
the mattress reservoir allergen level.31
Differences in allergen levels have also
been demonstrated for other synthetic
and feather bedding items, such as du-
vets. Thus, synthetic duvets were shown
to have about 15-fold higher Der p 1 con-
tent than feather duvets.32 That study also
confirmed the previous New Zealand find-
ings of higher allergen levels in synthetic
pillows.28 If synthetic duvets are present
on beds than composite bedding Der p 1
levels were found to be higher, but lower
in the presence of feather duvets.33 Other
studies have also shown higher house dust
mite allergen levels on mattresses associ-
ated with synthetic pillows34 or lower with
feather pillows.35
Why do synthetic bedding items have
higher levels of allergens compared to
feather bedding items? In order to keep
feathers inside feather pillows, manufac-
turers produce a cover with a tighter weave
than with synthetic pillows. We noted that
the more open weave of synthetic pillow
covers were large enough for house dust
mites to penetrate while they could not
penetrate feather pillows.36 We seeded
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adult life house dust mites on covers of a
standard polyester pillow, a newer type of
polyester/cotton pillow and a feather pil-
low and enumerated life house dust mites
remaining on top after 24 and 48 hours.37
All house dust mites had penetrated the
standard synthetic pillow cover after 24
hours while none had penetrated either
the newer type of synthetic pillow cover or
feather pillow cover after 48 hours. Addi-
tionally, the newer type of synthetic pillow
cover and the feather pillow cover were
less permeable to house dust than the
standard polyester pillow cover and, thus,
by implication to allergens. These find-
ings may explain the numerous reports
of higher house dust mite allergen levels
from synthetic bedding items.
The association of less asthma and al-
lergic diseases associated with feather bed-
ding and their lower levels of house dust
mite allergens could be due to the fact that
asthma severity is positively correlated to
house dust mite allergen levels of bedding,
where we spend about a third of our life
in close contact with our airways to bed-
ding items.38-40 New Zealand has some of
the highest bedding house dust mite al-
lergen levels in the world41 and one of the
highest prevalence rates of asthma in the
world.1,2 The latter may be related to the
high allergen levels although a secondary
intervention study of occlusive bedding
covers42 and a meta-analysis of allergen
reduction43 both failed to show a clinical
benefit in asthma. However, both these
studies have been criticized about their in-
clusion and exclusion criteria.44,45
Until lately, advice to house dust mite
sensitized patients was to avoid feather
bedding in the belief that this type of bed-
ding was favorable for house dust mites.
Nowadays, the feathers used are washed
and hot dried (>100 °C) ensuring that dust
mites present in raw feathers are killed and
their allergens denatured.46 True feather
allergy is rare and some reports of high
prevalence rates of feather allergy is most
likely due to contamination by house dust
mite allergens of feather extracts used in
skin prick testing.47
Fungi and their pro-inflammatory
compounds
Fungi in the home environment are asso-
ciated with respiratory health outcomes48
and mould sensitization has been associ-
ated with severe asthma requiring hos-
pitalisation.49,50 Recently, a UK study ex-
amined pillows for fungal contamination
and showed that they were substantially
contaminated with a great number of dif-
ferent species of fungi.51 Interestingly, one
species, Aspergillus fumigatus, was more
prevalent on synthetic pillows while an-
other species, Aureobasidium pullulans,
was more prevalent on feather pillows.
A major cell-wall component of fungi is
(1-3)-β-D-glucan (beta-glucan) account-
ing for more than half of its dry weight.
Beta-glucan is non-allergenic but pro-in-
flammatory. Beta-glucan has been associ-
ated with the development of respiratory
symptoms associated with exposure to
indoor fungi52 including increased peak
expiratory flow variability in children.53
Given the findings of fungal contamina-
tion of pillows51 we examined the beta-glu-
can content of pillows and whether there
were differences in these levels between
synthetic and feather pillows. Synthetic
pillows were found to contain about 4-fold
higher total amounts of beta-glucan than
feather pillows.54 This was reconfirmed in
a follow-up study determining beta-glu-
can content of bedding items in New Zea-
land.55 Additionally, synthetic duvets had
about 7-fold higher beta-glucan content
than feather duvets. Thus, higher synthet-
ic bedding levels of beta-glucan together
with their higher house dust mite allergen
levels may explain the adverse effects of
synthetic bedding on asthma symptoms.
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Volatile organic compounds
Strachan and Carey postulated that re-
lease of volatile organic compounds
(VOCs) from synthetic pillows and in-
creased mucosal permeability to allergens
leads to worsening of asthma symptoms.3
Indoor emissions of VOCs are known to
worsen asthma symptoms56 and can lead
to the development of bronchial obstruc-
tion in children.57 Synthetic pillows are
made with polyurethane foams that con-
tain isocyanates58 and isocyanates are a
well-known inducer of occupational asth-
ma caused by high exposure at work or by
sensitization.59 Thus, it is conceivable that
synthetic pillows could release VOCs over
time and thus, augment response to their
higher allergen levels. To the best of our
knowledge, no data has been published
on VOCs release from synthetic pillows or
lack thereof from feather pillows.
Endotoxin
Endotoxin from Gram-negative bacteria,
is present in mattresses and pillows.60,61
Higher bedroom endotoxin levels at birth
have been associated with increased
wheezing in infancy62 although other stud-
ies have shown a protective effect of en-
dotoxin exposure in early life and the de-
velopment of asthma.63 However, in those
with established asthma, severity of asth-
ma was related to indoor endotoxin ex-
posure.64 Furthermore, exposure to high
levels house dust mite allergens augments
endotoxin-induced airway inflammation
in subjects with atopic asthma.65 Therefore,
if there is a difference in endotoxin from
synthetic and feather bedding, this could
be another potential mechanism. To the
best of our knowledge, there has only been
one published study comparing endotoxin
levels between synthetic and feather pil-
lows that found no difference.66 However,
this was a small study and therefore sig-
nificant differences in endotoxin between
the two types of pillows may have been
missed. Also, there are no published stud-
ies on endotoxin levels from duvets and
this is an area that needs to be explored.
Conclusions
There is now considerable epidemiologi-
cal evidence from case-control and longi-
tudinal studies that synthetic bedding is
associated with asthma and allergic dis-
eases while feather bedding appears to
be protective. The mechanisms for these
effects are likely to be complex, involv-
ing both environmental and genetic in-
fluences. The higher allergen and fungal
pro-inflammatory compounds levels from
synthetic bedding are likely environmen-
tal influences. Further work is required to
determine whether VOCs from synthetic
bedding play a role. What are required
now are well-designed primary and sec-
ondary randomized-controlled trials of
synthetic and feather bedding in the pre-
vention and treatment of asthma and al-
lergic diseases.
Acknowledgements
Studies from the Wellington Asthma Re-
search Group have been supported in
main by research grants from the Health
Research Council of New Zealand, the
Wellington Medical Research Founda-
tion, the Child Health Research Founda-
tion of New Zealand and Lotteries Health
New Zealand. We thank all present and
past members of the Wellington Asthma
Research Group for their contributions to
the many studies.
Conflicts of Interest: The authors
declare they have no conflicts of interest
in relation to the contents of the article.
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www.theijoem.com Vol 2 Number 2; April, 2011 73
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