Allergens and asthma.

This article presents the studies that show that asthma in children is strongly associated with sensitization to dust mite and other indoor allergens. In addition, the recent evidence that this association reflects a causal relationship between allergen exposure and asthma is reviewed. The relevance of quantitative measurements of the major indoor allergens (dust mite, cockroach, and cat) in the houses of children with asthma is discussed. Finally, the increasing evidence that avoidance measures can be an effective treatment for asthma is considered together with the details about avoidance protocol for dust mite and cat allergen.     

Indoor environmental influences on children's asthma

The burden of asthma for children in the United States is substantial and has continued to rise for the past 2 decades. There is growing evidence that the indoor environment may play an important role in the pathogenesis of childhood asthma. This article first reviews the effects of indoor allergen exposure and sensitization on asthma incidence and morbidity, focusing on dust mite, cockroach, pet, and rodent allergens. It then addresses the effects of indoor air pollutants (ozone, particulate matter, nitrogen dioxide, environmental tobacco smoke, sulfur dioxide, and carbon monoxide) on asthma morbidity.     

Allergens in urban schools and homes of children with asthma

To cite this article: Permaul P, Hoffman E, Fu C, Sheehan W, Baxi S, Gaffin J, Lane J, Bailey A, King E, Chapman M, Gold D, Phipatanakul W. Allergens in urban schools and homes of children with asthma. Pediatr Allergy Immunol 2012: 23: 543-549. ABSTRACT: Background: Most studies of indoor allergens have focused on the home environment. However, schools may be an important site of allergen exposure for children with asthma. We compared school allergen exposure to home exposure in a cohort of children with asthma. Correlations between settled dust and airborne allergen levels in classrooms were examined. Methods: Settled dust and airborne samples from 12 inner-city schools were analyzed for indoor allergens using multiplex array technology (MARIA). School samples were linked to students with asthma enrolled in the School Inner-City Asthma Study (SICAS). Settled dust samples from students' bedrooms were analyzed similarly. Results: From schools, 229 settled dust and 197 airborne samples were obtained. From homes, 118 settled dust samples were obtained. Linear mixed regression models of log-transformed variables showed significantly higher settled dust levels of mouse, cat and dog allergens in schools than homes (545% higher for Mus m 1, estimated absolute difference 0.55?μg/g, p?相似文献   

Cockroach allergy in a group of Turkish children with respiratory allergies

Exposure to cockroach may lead to exacerbations of bronchial asthma and/or allergic rhinitis in sensitized patients. Although there is a widespread belief that cockroach allergy is a common problem in patients with respiratory allergies, little is known in Turkish children. In order to investigate the prevalence and characteristics of cockroach allergy in respiratory allergic children, we performed a study in newly referred children with respiratory allergies. All patients underwent questionnaire-interview and skin prick tested with common inhalant allergens in addition to two cockroach allergens: Blatella germanica (Bg) and Periplaneta americana (Pa). A subgroup of patients was also serologically investigated for specific IgE against Bg and house dust mite. Three hundred- and thirty-seven children aged 2-16 years were recruited for the study and 77.7% of these were atopic, with the most common indoor and outdoor allergens of house dust mite (47.5%) and grass pollens (45.1%), respectively. According to the prick test results, allergies to Bg and Pa were 11.9% and 7.4%, respectively, and there was a weak correlation between size of the prick test and specific IgE levels for Bg allergen. Almost 30% of the cockroach-sensitive patients were allergic to both cockroach antigens. Seventy percent of cockroach-sensitive patients were also sensitive to house dust mite, and only 1% were monosensitive. Dwellings in the Middle Anatolia and Black Sea regions were less commonly infested by cockroach compared to the dwellings in other regions. In conclusion, our preliminary study showed that cockroach sensitization is common among children with respiratory allergies irrespective of infestation history, suggesting that addition of cockroach allergen to the routine allergy screening panel is critical.     

Lung function at age 3 years: effect of pet ownership and exposure to indoor allergens

OBJECTIVE: To investigate the effect of pet ownership and exposure to indoor allergens on lung function in 3-year-old children. DESIGN: Birth cohort study. SETTING: Community. PARTICIPANTS: Children recruited prenatally and followed prospectively to age 3 years. MAIN OUTCOME MEASURES: Specific airway resistance (sRaw) (measured with body plethysmograph) at age 3 years; skin-prick tests; data on cat and dog ownership collected prospectively; allergen levels measured in dust collected from homes (high exposure defined as mite allergens >2 microg/g in mattress, and dog >10 microg/g and cat >8 microg/g allergens on the living room floor). RESULTS: There was no effect of cat or dog ownership at birth or age 3 years on lung function, and no association between lung function and mite, dog, or cat allergen exposure. Sensitized children exposed to high levels of sensitizing allergen had significantly poorer lung function (n = 49, sRaw kiloPascal per second [kPa/s]; geometric mean [GM], 1.20; 95% confidence interval [CI], 1.13-1.28) than children who were not sensitized and not exposed (n = 114; GM, 1.08; 95% CI, 1.04-1.12); not sensitized, but exposed (n = 282; GM, 1.07; 95% CI, 1.05-1.10); or sensitized and not exposed (n = 53; GM, 1.12; 95% CI, 1.06-1.18; P = .005). In a multivariate model, independent significant associates of lung function were maternal and paternal asthma, and the combination of sensitization and exposure to sensitizing allergen, with significant interaction between them. Lung function was substantially worse in sensitized and highly exposed children with both asthmatic parents (GM, 2.23; 95% CI, 1.68-2.97), compared with those with neither (GM, 1.09; 95% CI, 1.04-1.16) or just 1 of these features. CONCLUSIONS: Pet ownership, sensitization without exposure, or exposure in nonsensitized individuals have no effect on lung function. However, the combination of specific sensitization and exposure to sensitizing allergen is associated with significantly poorer lung function in early life.     

Childhood asthma and exposure to indoor allergens: lowmite levels are associated with sensitivity

The prevalence and level of sensitivity to indoor allergens were studied in relation to current exposure at home in 124 children with perennial asthma living in three climatic zones of Sweden. The house dust mite (HDM) allergen levels were higher in the South than in the North (p < 0.001), while cat and dog allergen levels tended to be higher in the North than the South (n. s.). Thirty-four percent of the children were sensitive to the HDM Dermatophagoides pteronyssinus , as determined by IgE antibodies in vitro, 27% were sensitive to D. farinae , 57% to cat and 55% to dog. Sensitivity to HDM was significantly more prevalent in Southern, than in Central and Northern Sweden (p=0.001) where the children were more often sensitive to pets (cat p=0.005, dog p= 0.002). A significant association between the concentration of Der p I and Derf I in the house dust and both the prevalence of sensitivity to HDM and the IgE antibody levels against mites was found even at concentrations well below the commonly suggested risk level for sensitisation of 2 μg/g dust. No relationship was found between pet allergen concentration in the home dust and sensitivity to pets, possibly because of exposure outside home, e. g. in schools and meeting places for leisure activities. Similarly, there was no consistent association between the level of mite or pet allergen exposure at home and asthma severity as judged by symptom and medication score. The study indicates that there is no threshold value for sensitisation to mite allergens in asthmatic children, and therefore, dust allergen levels at home should be kept as low as possible in homes of children at risk for asthma.     

Exposure to indoor allergens and development of allergy

House dust contains several indoor allergens which can elicit hypersensitivity and various atopic symptoms, especially in childhood. This review article focusses on house dust mite hypersensitivity to one of the most important species, Dermatophagoides , as a model. A clear dose-response relationship has been demonstrated between house dust mite allergen exposure in mattress dust samples and sensitization, i.e. serum IgE to Dermatophagoides and positive histamine release from basophil leukocytes to one of the major allergens from Dermatophagoides pteronyssinus, Der p I. 2 μg major allergen of Dermatophagoides /g of dust and 8 μg major allergen of cat/g of dust have been suggested to be threshold concentrations above which the risk of sensitization in genetically predisposed atopic children is significantly increased. Epidemiological studies showed house dust mite allergens to be one of the most important risk factors in the development of atopic airway disease. A relation between age at onset of the first wheezing episode and house dust mite allergen exposure at the age of 1 year has been observed. There are various factors influencing house dust mite growth, and many studies have been performed to reduce house dust mite allergen exposure. Until now, none of the approaches appeared to have achieved sufficient mite and mite allergen reduction.     

Allergenexposition und Asthmaentstehung

Background. There has been a tremendous increase in atopic diseases during the past 25 years in industrialized countries. Among other factor, high indoor allergen exposure (house dust mite Dermatophagoides, cat) was considered to be one major risk factor for the increase in asthma prevalence in childhood. MAS-90. In the German Multercentre Allergy Study (MAS-90) only an association between specific sensitization and exposure to house dust mite and cat allergens could be found. There was no association between the prevalence of asthma or wheeze at age 7 and indoor allergen exposure in early childhood. Discussion. Other genetic and exogenous factors seem to have a stronger influence on the development of childhood asthma.     

Environmental exposures and exhaled nitric oxide in children with asthma

OBJECTIVE: To evaluate the relation of environmental factors with exhaled nitric oxide (FENO) concentrations among asthmatic children. STUDY DESIGN: Cross-sectional analysis of 170 tobacco smoke-exposed children, ages 6 to 12 years, who have doctor-diagnosed asthma using measures of FENO, medication use, and exposures to settled indoor allergens and tobacco smoke. RESULTS: In multivariable analysis, child's age, uncarpeted flooring, not owning a cat, higher income, dust mite exposure, and being sensitized to any allergens were associated with higher FENO concentrations. Children who were sensitized to indoor allergens had an adjusted geometric mean FENO of 15.4 ppb (95% CI, 13.1, 18.2) compared with 10 ppb (95% CI, 8.2, 12.2) for unsensitized children. There was no statistically significant association of serum cotinine, hair cotinine, or reported corticosteroid therapy with FENO. CONCLUSIONS: FENO is higher among children who are sensitized to indoor allergens and exposed to dust mites. The results hold promise for the use of FENO as a tool to manage childhood asthma by using both pharmacologic and environmental treatments.     

Domestic allergen and endotoxin exposure and allergic sensitization in Cyprus

We investigated the relationship between domestic allergen and endotoxin exposure and allergic sensitization among children in Cyprus. We skin prick tested 128 children aged 15-16 yr (random samples of 85 children with self-reported asthma and 43 healthy controls) and measured their domestic exposure to endotoxin and allergens (mite, cat, and dog). We analyzed the data using multivariate logistic regression (adjusting for gender, area of residence and parental history) and presented the outcomes as odds ratios (OR) and 95% confidence intervals (CI). Among this selected population, 19% of children were sensitized to mite, 15% to cat and 7% to dog. Male gender (OR 2.74, 95% CI 1.18-6.38, p = 0.02), maternal history of allergic disease (OR 3.53, 95% CI 1.13-11.00, p = 0.03), increasing endotoxin (OR 1.58, 95% CI 1.00-2.49, p = 0.05) and residence in the district of Nicosia (OR 2.48, 95% CI 1.01-6.08, p = 0.05) were independent associates of allergic sensitization. Factors associated with mite sensitization were increasing Der p 1 and endotoxin exposure (OR 1.28, 95% CI 1.01-1.62, p = 0.04 and OR 1.76, 95% CI 1.01-3.08, p = 0.05, respectively) and living in an urban area (OR 6.80, 95% CI 1.37-33.67, p = 0.02). Sensitization to domestic pets was associated only with paternal allergic disease (cat: OR 5.68, 95% CI 1.57-23.56, p = 0.02; dog: OR 13.5, 95% CI 1.79-101.73, p = 0.01), but not with pet ownership or specific allergen or endotoxin exposure. In conclusion, mite allergen exposure was associated with sensitization to mite, but there was no association between cat and dog allergen exposure and specific sensitizations. Surprisingly, in this area, increasing endotoxin exposure was associated with an increased risk of sensitization.     

The use of mutually exclusive categories for atopic sensitization: A contrasting effect for family size on house dust mite sensitization compared with ryegrass sensitization

Our aim was to examine the relative importance of family size on sensitization to two different allergens: ryegrass and house dust mite (HDM), using a mutually exclusive classification for allergen-specific sensitization. An 8-year follow-up birth cohort study of children born between 1988–89 was conducted. The follow-up sample consisted of 498 children residing in Northern Tasmania in 1997 (84% of eligible). Outcome measures included skin prick test (SPT) reaction to nine aeroallergens and parental questionnaire. Family size was defined as sibling number in 1997. Children with a positive SPT to either Der p or Der f house dust mite but not ryegrass were classified as HDM-exclusive (n = 84). Children with a positive SPT to ryegrass but not HDM were classified as ryegrass-exclusive (n = 43). Family size was associated with reduced ryegrass-exclusive sensitization [AOR 0.57 (0.39, 0.84) per increase in sibling number] but not HDM-exclusive sensitization [AOR 0.97 (0.77,1.23)]. The difference in the family size effect on these sensitization outcomes was significant (p = 0.02). Similarly, family size tended to be associated with reduced asthma among ryegrass-exclusive sensitized children [AOR 0.45 (0.18,1.12)] but not HDM-exclusive sensitized children [(AOR 1.46(0.80–2.65)]. Large family size was strongly associated with reduced sensitization for ryegrass allergens but not HDM allergens using mutually exclusive sensitization categories. If this difference is confirmed in other studies, the contrasting effect of family size may reflect differences between these allergens with regard to level or timing of early life exposure, differences in allergen -specific potentiation for sensitization or unidentified confounding. The use of mutually exclusive categories for allergen sensitization will assist future work on child atopic disease.     

Randomized trial to prevent sensitization to mite allergens in toddlers and preschoolers by allergen reduction and education: one-year results

OBJECTIVE: To evaluate the effectiveness of prevention measures against dust mite sensitization. DESIGN: European (England, Germany, Greece, Lithuania) multicenter prospective single-blind randomized control trial with a follow-up of 12 months. PARTICIPANTS: Toddlers and preschoolers, with at least 1 parent with atopic symptoms and sensitization, who initially were not sensitized to mite allergens. INTERVENTIONS: A combination of education and a simple preventive measure (mattress encasement) to reduce mite allergen exposure. SETTING: Community-based study. MAIN OUTCOME MEASURES: Sensitization to mite allergens (skin-prick test or specific immunoglobulin E). RESULTS: Of 636 children (mean age, 3.1 years) included in the study, 566 (89%) participated in the first-year follow-up. The incidence of sensitization to mite allergens was 10 (3%) of 330 in the intervention vs 20 (6.5%) of 306 in the control arm, including loss of follow-up (intention-to-treat principle). Allergic symptoms were more common in sensitized than in nonsensitized children and so was the prevalence of physician-diagnosed asthma, eczema, and food allergy. CONCLUSIONS: This simple, harmless, and inexpensive measure can be used in toddlers and preschoolers of parents with atopic disorders to reduce sensitization to mite allergens. With regard to clinical manifestations of atopy, follow-up studies are needed to determine the effectiveness of the intervention.     

House dust mite allergen reduction and allergy at 4 yr: Follow up of the PIAMA-study

Exposure to high allergen levels in early life is a risk factor for the development of allergy. We previously reported limited effects of mite allergen impermeable mattress covers in the prevention and incidence of asthma and mite allergy (PIAMA) cohort at the age of 1 and 2 yr. We now present the results of follow-up at 4 yr objectives. To examine the effects of early reduction of house dust mite (HDM) allergen exposure by means of mattress covers on the incidence of allergy and asthma symptoms in the PIAMA birth cohort at the age of 4 yr. High-risk children (allergic mother) were prenatally recruited and randomly allocated to three groups; receiving mite allergen impermeable mattress covers (n = 416), placebo covers (n = 394) or no intervention (n = 472). At 4 yr of age, atopy was assessed by questionnaire; specific Immunoglobulin E (IgE) to inhalant and food allergens was measured in serum. Dust samples collected from the children's mattresses were analysed for mite allergens. Dermatophagoides farinae1 allergen (Der f 1) levels in dust were reduced in the active group. However, Dermatophagoides pteronissinus 1 (Der p 1) levels, sensitization and atopic symptoms were similar in all groups. We found no effect of mite allergen impermeable mattress covers on sensitization and atopy at 4 yr. Moreover, the allergen reducing effects of the covers had disappeared for one of the two mite allergens that were measured.     

Predictive features for persistence of atopic dermatitis in children

Allergen exposure plays an important role in atopic dermatitis (AD). Because immunological mechanisms underlying asthma and AD have great similarities, we evaluated whether features such as allergen sensitization, immune response, disease severity and duration or allergen exposure could be considered predictive for AD persistence. Seventy-one AD children (age range 14–158 months) were enrolled and followed for 3 consecutive years for AD severity using the SCORAD index (SI). At enrollment, reactivity to inhalant and food allergens using the skin prick test (SPT) and house dust mite (HDM) atopy patch test (APT), and HDM allergens in house dust were evaluated. After 3 years, 38 children outgrew their AD (AD^– group), while in 33 AD persisted (AD⁺ group). At enrollment, AD⁺ children had a higher SI, higher rate of positivity to SPT and APT for mites (p = 0.001), and higher environmental exposure to HDM allergens (p = 0.035). The AD⁺ children developed more respiratory symptoms in comparison to AD^– children (p < 0.001). None of the AD^– children presented APT positivity. In our study population, positivity of SPT and APT for HDM, environmental allergen exposure levels and severity of the disease at enrollment presented a significant predictive power towards AD persistence. Subjects with positive skin reactivity to HDM should be considered at risk of AD persistence and of possible development of allergic respiratory disorders.     

Prenatal exposure to mite and pet allergens and total serum IgE at birth in high-risk children

To examine the relationship between prenatal exposure to mite, cat and dog allergens and total serum IgE at birth in newborns at high risk of asthma. In the homes of 221 newborns with at least one first-degree relative with asthma, concentrations (ng/g dust) of allergens of house dust mite (mite), cat and dog were measured at the fourth to sixth month of pregnancy in dust samples from the maternal mattress and living room. At day 3-5 after birth, total IgE was measured in capillary heel blood. A total number of 174 blood samples were available (11 mothers refused newborn's blood sampling, and in 36 cases the blood sample was too small for analysis). In 24% of the newborns, total IgE was elevated (cut-off value 0.5 IU/ml). A significant dose response relationship was found between increasing mite allergen levels [divided in quartiles ng/g dust (qrt)] and the percentage of elevated IgE: first qrt (0-85 ng/g) 13%; second qrt (86-381) 19%; third qrt (382-2371) 26%; fourth qrt (> or =2372) 42%, respectively, p=0.01. This relationship remained significant after adjusting for passive smoking, maternal and paternal mite allergy, socio-demographic factors, birth characteristics and (breast) feeding practice in the first week of life. In high-risk newborns, prenatal exposure to mite allergens, but not to cat and dog allergens from dust of the living room and of the maternal mattress was associated with total serum IgE at birth.     

Building characteristics affect the risk of allergy development

Damp dwellings increase the risk for house dust mite (HDM) infestation in temperate climate zones and may be associated with an increased risk for allergic disease. The aim of the study was to assess possible relationships between allergen levels in house dust, characteristics of residence buildings and allergic diseases in children. A subsample of 12-yr-old children, having the same address in 1991 and 1996, was selected from a population-based sample of children from the Göteborg area. Health inspectors examined the residences of all the 109 children and several different building characteristics including humidity and indoor temperature were collected. Dust samples for analysis of HDM allergens were collected from the children's beds, and for analysis of cat and dog allergens from the living room. Current health status was assessed by questionnaires, interviews and skin prick tests (SPT). Dog or cat allergens were found in all houses, even in houses without such animals. HDM allergens were found in 60% of the houses, but only six of them had levels exceeding 2 μg/g dust. There was a strong association between HDM-infestation and wheeze, but not with specific sensitization to HDM. The type of building (houses when compared with flats), the ventilation system and the presence of a basement had all major implications on respiratory symptoms, atopy and HDM infestation. We can conclude that dog or cat allergens were found in all houses, and a strong association between HDM infestation and indoor environment. Building construction affected both respiratory morbidity and sensitisation independently, suggesting not only worsening of symptoms but also a causative relationship with disease development.     

Eosinophils and eosinophil cationic protein in children with and without sensitization to inhalant allergens

Eosinophil inflammation is a common feature of allergic disorders and particularly in allergic asthma interest has been paid to related markers. In a communitybased survey of 10-year-old children, the association of eosinophil count (EC) and serum eosinophil cationic protein (ECP) with allergic sensitization, clinical history and exposure to mite allergen was studied. Relying on the results of skin prick tests, the children were divided to three groups: (1) children showing no sensitization to one of the seven inhalant allergens (n=16); (2) children with sensitization to at least one of five non-mite allergens (n=16); and (3) children with sensitization to mite allergens (n-75). Clinical history of asthma and hay fever was ascertained using standardized questionnaires. EC in peripheral blood and serum ECP were measured on one single occasion. Prior to blood sampling, mite allergen exposure at home had been assessed by taking dust samples and measuring the mite antigen concentration by means of an enzyme immunoassay. Compared to group 1, higher ECs were obvious in group 2 (P=0.037) and in group 3 (P=0.0013). Regarding serum ECP, higher levels occurred in group 2 (P=0.0033) as well as in group 3 (P=0.0001) when comparing them to the reference group. Sensitized children with neither asthma, nor asthma-like symptoms, nor hay fever (n=28) did not have significantly lower ECs and serum ECP levels than those with hay fever (n=15;P=0.09,P=0.17) and those with asthma (n=22;P=0.69,P=0.64). Since mild asthmatics were in general included, our findings were limited with regard to clinical severity. Using multiple linear regression, EC occurs in positive association with mite allergen exposure at home (P=0.033) and with a history of asthma-like symptoms (P=0.02).Conclusion Our findings indicate that EC and serum ECP are confounded by the status of allergic sensitization. Therefore, value and limits of both parameters need further investigation before use in the management of allergic children can be recommended.     

Concentrations of cat (Fel d 1), dog (Can f 1) and mite (Der f 1 and Der p 1) allergens in the clothing and school environment of Swedish schoolchildren with and without pets at home

To investigate whether our hypothesis that cat and dog owners bring allergens to public areas in their clothes was true or not, we studied the levels of Fel d 1, Can f 1, Der p 1 and Der f 1 in dust from the clothes and classrooms of children in a Swedish school. We also investigated the levels of allergen in different areas in the four classrooms used by the children. Thirty-one children were selected in four classes, forming three groups: cat owners, dog owners and children without a cat or dog at home. Furthermore, a group of children with asthma was included. Cat and dog allergens were detected in all 57 samples from clothes and classrooms. Mite allergen Der f 1 was detected in low concentrations in 6 out of 48 and Der p 1 in 5 out of 46 samples investigated. The concentrations of Can f 1 were higher than those of Fel d 1 in samples from clothes (geometric mean: 2676 ng/g fine dust and 444 ng/g) and classrooms (Can f 1: 1092 ng/g, Fel d 1: 240 ng/g). The dog owners had significantly higher concentrations of Can f 1 (8434 ng/g fine dust) in their clothes than cat owners (1629 ng/g, p <0.01), children without cat or dog (2742 ng/g, p < 0.05) and children with asthma (1518 ng/g, p < 0.001). The cat owners did not have significantly higher levels of Fel d 1 (1105 ng/g) in their clothes compared to the other three groups (D: 247 ng/g, nCnD: 418 ng/g, A: 386 ng/g) but the levels were significantly higher than for all children without a cat at home (345 ng/g, p < 0.05). No concentrations of mite allergen and low concentrations of Fel d 1 and Can f 1 were found in the children's hair. There were significantly higher concentrations of Fel d 1 and Can f 1 in dust from curtains than in samples from floors and bookshelves (p < 0.05). There was no significant difference between the allergen concentrations in samples from curtains and from desks and chairs, including the teachers' chairs, the only upholstered furniture in the rooms. Our results support the hypothesis that cat and dog owners bring allergens to public areas in their clothes and support other studies showing that textiles and upholstered furniture function as reservoirs of cat and dog allergens. Thus, children with asthma and other allergic diseases will be exposed to cat and dog allergens at school and by contact with pet owners, even if they avoid animal allergens at home.     

Risk factors, clinical and laboratory aspects of asthma in children

OBJECTIVE: To evaluate the clinical and laboratory aspects and the risk factors associated with asthma in children treated at the Pediatric Outpatient Clinic of Hospital Universitário Júlio Müller. METHODS: A case-control study including 59 asthmatic children (cases) and 104 nonasthmatic children (controls). The following factors were considered for risk analysis: parent? level of education, domestic exposure to allergens, passive smoking, breast feeding, low income, and family history of allergy. Samples of blood were collected for hemogram and to determine the total serum IgE as well as the one specific to allergens. Immediate hypersensitivity skin tests were performed with puncture for the detection of the following allergens: house dust mite, animals, molds, and cockroaches with positive (histamine) and negative controls (physiologic solution). A logistic regression model was used to calculate the odds ratio (OR) and 95% confidence intervals (95%CI) adjusted for risk factors and for confounding factors. RESULTS: Among the risk factors studied, sex, parent? low level of education, low income, length of the breast feeding period, and passive smoking were not associated with the presence of asthma. The domestic exposure to allergens was similar in both groups except for the higher frequency of pets at the homes of control patients (chi-square=16.9; P<0.05). Paternal history of rhinitis was the only association with asthma (OR=3.33; 95%CI: 1.03-11.17; P<0.05). The asthmatic children presented higher frequency of positive reactions to skin tests than the controls, mainly to house dust mites: Dermatophagoides pteronyssinus (69.5%), Dermatophagoides farinae (59.3%) and Blomia tropicalis (59.3%); cockroaches: Periplaneta americana (59.3%), and cat: Felis domesticus (37.3%), with OR between 11.2-21.0; P<0.05. Eosinophilia and serum levels of total IgE were more elevated in the group of asthmatic children (P<0.05). The positivity of the specific IgE test for Dermatophagoides pteronyssinus and Blomia tropicalis was higher in the cases than in the controls (P<0.05). The multivariate analysis showed that sensitization to the allergens produced by cockroaches (OR=9.26; 95%CI: 2.59-33.4), animals (OR=3.93; 95%CI: 1.05-14.67) and house dust mites (OR=3.74; 95%CI: 1.18-11.8) were the most important risk factors for asthma. CONCLUSIONS: The sensitization to indoor allergens, mainly to house dust mites, cockroaches, and cats showed a strong association with asthma in this study.     

Seasonal variations in house dust mite allergens--significance for children with allergy

Allergenic proteins of the house dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae and their major allergens Der p I and Der f I are one of the most significant environmental factors which may facilitate sensitization and allergic airway disease in childhood. In order to measure seasonal variations of mite allergen exposure, we collected mattress dust samples monthly in 13 homes over a period of 1 year. Der p I and Der f I were determined with a sandwich type ELISA. Mite allergen levels were significantly lower from January-June than from July-December (p less than 0.05) which was mostly due to Der p I variations. Only in 6 of the studied homes seasonal variations in mite allergen concentrations according to seasonal variations in outdoor humidity could be observed. In 7 homes mite allergen exposure stayed constant and seemed to depend only on indoor climate factors.