Exposure to indoor allergens in homes of patients with asthma and/or rhinitis in southeast Brazil: effect of mattress and pillow covers on mite allergen levels.

Abstract

Exposure and sensitization to indoor allergens have been associated with the development of asthma and other allergic diseases in many parts of the world. It is important to establish the degree of exposure, and to evaluate whether allergen control measures are effective in a particular area.
Concentrations of major allergens of mites, cockroach, cat and dog were measured in dust samples from homes of 24 mite-allergic patients living in Ribeirão Preto, Brazil. Allergen concentrations were quantitated by monoclonal antibody-based ELISA. Mite-impermeable mattress and pillow covers were applied to beds in the homes of 19 of the 24 patients, and group 1 mite allergen levels were measured 1 and 6 months following intervention.
Patients were exposed to high concentrations of mite allergens in their homes. 87.5% of the homes presented concentrations of group 1 allergens >10 microg/g of dust in at least one site. Cockroach allergen concentrations were low in most samples. Dog allergen concentrations were significantly higher in homes with dogs as compared to those without dogs. Mean concentrations of cat allergen were 0.1 microg/g. Mite allergen concentrations in bedding samples dropped from 24 microg/g at baseline to 0.9 and 1.0 microg/g, respectively, 1 and 6 months following encasement of mattresses and pillows.
Significant mite allergen reduction can be achieved in an area of high degree of exposure to mite allergens. Further studies evaluating the effect of this reduction on symptoms and airway inflammation will be necessary to establish the effectiveness of mite avoidance measures in our area.

Full text

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Original Paper
Int Arch Allergy Immunol 2004;133:365–370
DOI: 10.1159/000077356
Exposure to Indoor Allergens in Homes of
Patients with Asthma and/or Rhinitis in
Southeast Brazil: Effect of Mattress and Pillow
Covers on Mite Allergen Levels
Ka ´tia R.C. Tobiasa
L. Karla Arrudab
Virginia P.L. FerrianiaMartin D. Chapmanc
Departments of aPediatrics and bInternal Medicine, School of Medicine of Ribeira ˜o Preto, University of Sa ˜o Paulo,
Ribeira ˜o Preto, Brazil; cIndoor Biotechnologies Inc., Charlottesville, Va., USA
Received: April 3, 2003
Accepted after revision: November 7, 2003
Published online: March 17, 2004
Correspondence to: Dr. L. Karla Arruda
Faculdade de Medicina de Ribeira ˜o Preto, Departamento de Pediatria
Avenida Bandeirantes 3900
Ribeira ˜o Preto, SP 14049-900 (Brazil)
Tel. +55 16 602 2902, Fax +55 16 602 2297, E-Mail karla@fmrp.usp.br
ABC
Fax +41 61 306 12 34
E-Mail karger@karger.ch
www.karger.com
© 2004 S. Karger AG, Basel
Accessible online at:
www.karger.com/iaa
Key Words
Mites W Asthma W Dermatophagoides pteronyssinus W
Indoor allergens W Mite avoidance
Abstract
Background: Exposure and sensitization to indoor aller-
gens have been associated with the development of
asthma and other allergic diseases in many parts of the
world. It is important to establish the degree of exposure,
and to evaluate whether allergen control measures are
effective in a particular area. Methods: Concentrations of
major allergens of mites, cockroach, cat and dog were
measured in dust samples from homes of 24 mite-aller-
gic patients living in Ribeira ˜o Preto, Brazil. Allergen con-
centrations were quantitated by monoclonal antibody-
based ELISA. Mite-impermeable mattress and pillow
covers were applied to beds in the homes of 19 of the 24
patients, and group 1 mite allergen levels were mea-
sured 1 and 6 months following intervention. Results:
Patients were exposed to high concentrations of mite
allergens in their homes. 87.5% of the homes presented
concentrations of group 1 allergens 110 Ìg/g of dust in at
least one site. Cockroach allergen concentrations were
low in most samples. Dog allergen concentrations were
significantly higher in homes with dogs as compared to
those without dogs. Mean concentrations of cat allergen
were 0.1 Ìg/g. Mite allergen concentrations in bedding
samples dropped from 24 Ìg/g at baseline to 0.9 and
1.0 Ìg/g, respectively, 1 and 6 months following encase-
ment of mattresses and pillows. Conclusions: Significant
mite allergen reduction can be achieved in an area of
high degree of exposure to mite allergens. Further stud-
ies evaluating the effect of this reduction on symptoms
and airway inflammation will be necessary to establish
the effectiveness of mite avoidance measures in our
area.
Copyright © 2004 S. Karger AG, Basel
Introduction
Exposure and sensitization to indoor allergens have
been associated with the development of asthma and oth-
er allergic diseases in many parts of the world [1]. In Bra-
zil, 80 and 55% of children with asthma and/or rhinitis
present positive skin prick tests to mites and cockroach,
respectively [2]. A dose-response relationship between
allergen exposure and development of sensitization has
been consistently established for mite and cockroach

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Tobias/Ferriani/Chapman/Arruda
allergens [1, 3]. Strategies for management of allergic
patients include recommendations on reduction of aller-
gen concentrations in the environment [4, 5].
Large reductions in mite allergen exposure occur in
studies conducted in hospitals or in high-altitude sanato-
ria [6, 7], resulting in significant improvement of symp-
toms and nonspecific bronchial hyperreactivity. How-
ever, controlled studies in homes of children and adults
have provided conflicting results [8]. Recent studies have
failed to show major benefits of successful reduction of
mite allergens in causing a decrease in asthma or atopic
dermatitis symptoms in patients with well-established
disease, or in preventing the development of respiratory
symptoms, atopic dermatitis or atopic sensitization in
early childhood [9, 10]. On the other hand, other well-
controlled studies have provided evidence of a beneficial
effect [11–16]. Mite avoidance studies have been targeted
at reducing allergen levels in the bedroom by applying
mite-impermeable mattress and pillow covers to patients’
beds and removing carpets, which are established mea-
sures for control of dust mite exposure [17].
Assessing allergen exposure and defining which envi-
ronmental control measures are effective in a particular
environment are initial steps to understanding the role of
allergen avoidance in causing improvement of symptoms,
bronchial hyperreactivity and quality of life in allergic
patients. The aims of the present study were to quantitate
allergen exposure to mites, cockroach, cat and dog in
homes of mite-allergic patients living in Ribeira ˜o Preto,
Brazil, and to study the effectiveness of applying mattress
and pillow covers to the beds of mite-allergic patients with
regard to reducing mite allergen concentrations over
time.
Patients and Methods
Patients
Twenty-four patients, aged 4–37 years (13 males), were selected
for the present study. Thirteen had asthma and rhinitis, 4 had asthma
only, 6 had allergic rhinitis only and 1 had atopic dermatitis. Four-
teen of the patients were children 4–13 years old, and 10 were adults,
seen at the Allergy Clinic of the School of Medicine of Ribeira ˜o Pre-
to, University of Sa ˜o Paulo, Brazil. Patients were selected based on
the presence of a positive skin prick test to a Dermatophagoides pte-
ronyssinus extract (Bayer, Spokane, USA; 10,000 AU/ml). All pa-
tients or their caregivers gave informed consent to participate in the
study. The study was approved by the Ethical Committee of the Clin-
ical Hospital of the institution.
Allergen Concentrations in House Dust Samples
Patients living in Ribeira ˜o Preto, southeast Brazil, had their
homes visited for collection of dust samples. Eight of 23 homes were
apartments, and all homes were uncarpeted. Dust collection and
preparation of dust extracts were performed according to standard
procedures [18]. Briefly, dust samples were collected from four sites
in each home, i.e. bedding, bedroom floor, TV room and kitchen,
using a portable vacuum cleaner (Electrolux Compact Plus). Vacu-
uming of bed sheets and pillow covers was performed, followed by
vacuuming of the entire mattress surface and both sides of the pil-
low(s). One hundred milligrams of sieved dust were extracted over-
night at 4°C in 2 ml of phosphate-buffered saline, and measurements
of major allergens from mites (Der p 1, Der f 1 and group 2), cock-
roach (Bla g 1 and Bla g 2), cat (Fel d 1) and dog (Can f 1) were carried
out using monoclonal antibody-based ELISA, as previously de-
scribed [18–21].
Effect of Mite-Impermeable Mattress and Pillow Covers on Mite
Allergen Levels in Bedding Samples
Mite-impermeable mattress and pillow covers, kindly provided
by LUFT (Sa ˜o Paulo, Brazil), were randomly distributed to 19 of the
24 patients, and applied to the mattress and pillow in the patient’s
bedroom. In keeping with current recommendations for decreasing
mite allergen exposure [17], patients from our clinic are routinely
instructed to wash bed sheets at least once a week and blankets twice
a month, upon diagnosis of mite allergy. Patients in the present study
did not receive any further instructions regarding bedding care
besides those already provided at clinical visits, and were asked to
avoid washing bedding for at least 24 h prior to the home visit. Mite
allergen concentrations (Der p 1 and Der f 1) were measured by
monoclonal antibody-based ELISA [18] 1 and 6 months following
placement of mattress and pillow encasings. A reduction in the con-
centration of group 1 mite allergens equal to or greater than 90% was
considered significant.
Statistical Analysis
The Kruskal-Wallis test was used to compare allergen concentra-
tions in different areas of the home. Comparisons of Der p1 and Der
1 concentrations in paired samples, and assessment of differences in
concentrations of group 1 mite allergens before and after placement
of mattress and pillow encasings were carried out using the Wilcoxon
test. Concentrations of dog allergen in homes with and without dogs
were compared by the Mann-Whitney test. The INSTAT 2 software
was used for statistical analysis and the GraphPad Prism 3.0 program
was used for construction of graphs.
Results
Levels of Der p 1 and Der f 1 in 93 samples collected
from four sites (bedding, bedroom floor, TV room and
kitchen) in the homes of 24 allergic patients are shown in
figures 1a and b. Der p 1 levels were significantly higher in
bedding samples [geometric mean (GM) 1.0 Ìg/g of dust]
as compared to bedroom floor and kitchen samples (GM
0.12 and 0.03 Ìg/g, respectively; p ! 0.05). In addition,
Der p 1 levels in the TV room (GM 0.54 Ìg/g) were signif-
icantly higher than those in kitchen samples (p ! 0.001).
Similarly, Der f 1 levels were significantly higher in bed-
ding samples (GM 10.2 Ìg/g) as compared to bedroom

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Int Arch Allergy Immunol 2004;133:365–370
367
floor and kitchen samples (GM 0.3 and 0.09 Ìg/g, respec-
tively; p ! 0.001). Der f 1 levels were also higher in TV
room (GM 2.3 Ìg/g) as compared to kitchen samples (p !
0.001). In bedding and TV room samples, Der f 1 levels
were significantly higher than Der p 1 levels (Wilcoxon
test, p = 0.003 and p = 0.02, respectively). Group 1 aller-
gens were highest in bedding samples (GM 17.8 Ìg/g), fol-
lowed by TV room (GM 2.4 Ìg/g), bedroom floor (GM 0.3
Ìg/g) and kitchen samples (GM 0.1 Ìg/g). Overall, expo-
sure to group 1 allergens at levels 110 Ìg/g in at least one
site was observed in 87.5% of the patients’ homes. In
addition, there was a significant correlation of levels of
group 1 and group 2 allergens in dust samples (n = 93, r =
0.26, p = 0.005, data not shown). Mite allergen concentra-
tions were high and comparable to those reported in other
cities in Brazil or in other countries (table 1).
Cockroach allergen concentrations were low, ranging
from undetectable (!0.2 U/g) to 14.6 and 9.6 U/g of dust
for Bla g 1 and Bla g 2, respectively. Only 20.8 and 12.5%
Fig. 1. Der p 1 (a) and Der f 1 (b) concentrations in dust samples
from homes of patients with asthma and/or rhinitis living in Ribeira ˜o
Preto, Brazil. Concentrations of Der p 1 and Der f 1 were significant-
ly higher in bedding samples as compared to bedroom floor and
kitchen samples (p ! 0.05). In addition, Der p 1 and Der f 1 levels in
TV room samples were significantly higher than those in kitchen
samples (p ! 0.001). In bedding and TV room samples, Der f 1 levels
were significantly higher than Der p 1 levels (Wilcoxon test, p !
0.05). The number of samples with undetectable levels of allergen
(! 0.02 Ìg/ml) is indicated directly below the graphs.
Table 1. Comparison of mite allergen
concentrations in dust samples from homes
in Ribeira ˜o Preto to concentrations
reported from other countries and other
areas of Brazil
AllergenLocationMean level
of mite
allergen, Ìg/g
Report
Der p 1
Der p 1
Der p 1
Der p 1
Der p 1
Der p 1
Der p 1
Der f 1
Der p 1
Der f 1
Poole, England, UK
Wellington, New Zealand
Sydney, Australia
Charlottesville, Va., USA
Sa ˜o Paulo, Brazil
Sa ˜o Paulo, Brazil
Uberlândia, Brazil
Uberlândia, Brazil
Ribeira ˜o Preto, Brazil
Ribeira ˜o Preto, Brazil
16.1
46.6
38.9
16.6
38.4
22.2
2.8
15.8
1.0
10.2
Sporik et al. 1990 [22]
Wickens et al. 1997 [23]
Marks et al. 1995 [24]
Sporik et al. 1999 [25]
Arruda et al. 1991 [26]
Rizzo et al. 1993 [27]
Sopelete et al. 2000 [28]
Sopelete et al. 2000 [28]
present study
present study

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Fig. 2. Concentrations of dog allergen Can f 1 in dust samples from
homes with and without dogs. Dog allergen concentrations were sig-
nificantly higher in samples collected from the 11 homes with dogs as
compared to those without dogs (n = 13 homes).
Fig. 3. Effect of mite-impermeable mattress and pillow covers on
mite allergen concentrations in bedding samples. After 1 and 6
months, there was a significant reduction of group 1 mite allergen
concentrations in bedding samples as compared to baseline levels
(p ! 0.0001).
of the homes, respectively, contained concentrations of
Bla g 1 and Bla g 2 equal to or greater than 8 U/g in at least
one site of the home (data not shown). In addition, no
significant differences were observed with regard to con-
centrations in the four sites of each patient’s home.
Seventy-six samples were available for Can f 1 mea-
surements. As expected, dog allergen concentrations were
significantly higher in samples collected from the 11
homes with dogs, as compared to those without dogs (GM
3.3 and 0.4 Ìg/g, respectively; p ! 0.0005) (fig. 2). None of
the homes had cats; however, cat allergen Fel d 1 could be
detected in very low concentrations in most samples
(GM: bedding 0.18 Ìg/g; bedroom floor 0.07 Ìg/g; TV
room 0.1 Ìg/g; kitchen 0.03 Ìg/g) (data not shown).
In a subgroup of 19 of the 24 patients, the effect of
mite-impermeable mattress and pillow covers on group 1
allergen concentrations was evaluated. After 1 and 6
months, there was a significant reduction of group 1 mite
allergen concentrations in bedding samples (GM 0.9 and
1 Ìg/g, respectively) as compared to baseline levels (GM
24.2 Ìg/g; p ! 0.0001) (fig. 3). Reduction of mite allergen
concentrations equal to or greater than 90% was observed
in 74 and 68% of the samples analyzed 1 and 6 months,
respectively, following the use of encasings.
Discussion
Patients living in Ribeira ˜o Preto have high concentra-
tions of group 1 mite allergens in their beds, as previously
shown [24–26]. Placement of mattress and pillow encas-
ings resulted in significant and sustained reduction of
mite allergen levels in bedding samples. It would be
unlikely that reductions in allergen levels of the magni-
tude we observed for most samples in our study could
have occurred after 1 month, regardless of any interven-
tion. Rizzo et al. [29] analyzed dust samples from homes
of mite-allergic children living in the city of Sa ˜o Paulo,
Brazil, at monthly intervals over a period of 1 year. They
showed that Der p 1 concentrations remained high, with-
out significant variations throughout the study, and that
there was no significant correlation of Der p 1 levels with
patients’ symptom scores [29].
Our previous studies in the city of Sa ˜o Paulo, Brazil, in
the early 1990s revealed that children with asthma were
exposed to high levels of Der p 1 in their homes, and that
Der f 1 levels were undetectable or very low in most sam-
ples. However, our current results showed a significantly
higher frequency of dust samples containing levels of Der
f 1 110 Ìg/ml as compared to Der p 1. Similar results

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have also been reported by Sopelete et al. [28], studying
adult patients living in the city of Uberlândia, Brazil. Dif-
ferences in climate, housing conditions or lifestyle may
account for the variation in the profile of allergen distri-
bution in different cities in Brazil. The results indicate
that studies aimed at evaluating environmental exposure
to mites in Brazil should include measurements of both
Der p 1 and Der f 1 allergens.
Concentrations of cockroach allergens were surprising-
ly low in our study. Previously, we reported that 55% of
children with asthma and/or rhinitis attending Pediatric
Allergy clinics in a university setting in Ribeira ˜o Preto
and Sa ˜o Paulo presented positive skin prick tests to cock-
roach (Blattella germanica and/or Periplaneta america-
na) [2]. A dose-response relationship between exposure to
cockroach allergen in the bedroom and sensitization to
cockroach has been determined [3]. In addition, the com-
bination of exposure to cockroach allergens in the home
and sensitization has been associated with increased mor-
bidity in children with asthma living in inner cities in the
United States [30]. In our community, P. americana is the
dominant species found indoors. However, assessment of
cockroach exposure was carried out by quantitation of B.
germanica allergens Bla g 1 and Bla g 2, using available
assays. Although a homologue of Bla g 1 with a high
degree of sequence identity has been described in P. ame-
ricana (Per a 1 allergen) [31, 32], it is possible that our
assays have underestimated exposure to cockroach aller-
gens in our area. Alternatively, skin test positivity in our
patients may be due to IgE responses to cross-reactive
allergens produced by mites. Tropomyosin, a pan-allergen
described in cockroaches and other invertebrates, as well
as other allergens, may play a role in IgE cross-sensitiza-
tion [33]. Recently, IgE-binding epitopes were identified
in Blomia tropicalis tropomyosin (Blo t 10) [34]. This mite
allergen shares up to 96% amino acid sequence identity
with tropomyosin of Dermatophagoides mites [34].
Animal allergens were detectable in most samples in
our study. Recently, striking differences have been shown
in concentrations of pet allergens in homes in the United
Kingdom and in Ghana, Africa. Despite similar rates of
pet ownership, concentrations of cat and dog allergens in
homes in Ghana were 275 and 75 times lower, respective-
ly, than concentrations in homes with pets in the UK. In
addition, allergen concentrations in homes with pets in
Ghana were lower than or comparable to those in homes
without pets in the UK [35]. Concentrations of dog aller-
gen in homes with dogs in our study were also lower than
those in homes in the UK (6.7 times lower), probably due
to the fact that in Brazil, as well as in Ghanaian communi-
ties, pets are predominantly kept outdoors. In addition,
differences in housing conditions, including the presence
of carpets and upholstered furniture, may favor indoor
accumulation of animal allergens in homes in the UK.
Mean concentrations of cat allergen in homes without cats
in our study were comparable to those in homes in
Ghana.
In conclusion, we have shown that mite-allergic pa-
tients living in Ribeira ˜o Preto, southeast Brazil, are ex-
posed to high concentrations of mite allergens in their
homes. Application of antiallergic mattress and pillow
covers to the beds of these patients resulted in a substan-
tial decrease in mite allergen exposure in carpet-free
bedrooms. Further studies aimed at investigating the role
of mite allergen reduction in improving the symptoms
and quality of life of mite-allergic patients will be impor-
tant to determine whether mite avoidance measures are of
clinical benefit to patients in our area.
Acknowledgments
The authors wish to thank Dr. Cândida Rizzo for helpful sugges-
tions on statistical analysis. We also thank Mrs. Sandra Jorda ˜o
(LUFT, Sa ˜o Paulo, Brazil) for providing the mattress and pillow cov-
ers to the patients who participated in the study. This study was sup-
ported by FAPESP (grant No.1995/9690-0), CAPES, Brazil, and
NIH grants No. AI32565 and AI34607.

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