Contribution of dust mite and cat specific IgE to total IgE: relevance to asthma prevalence

BACKGROUND: The prevalence of asthma is strikingly different in some Westernized countries: approximately 20% in New Zealand and approximately 8% in northern Sweden. OBJECTIVE: We investigated differences in total IgE and in the prevalence of wheezing related to the observation that high exposure to dust mite allergens induces high titers of IgE antibodies. METHODS: Two age-matched, population-based cohorts-1155 children in New Zealand (224 sera) and 3431 children (797 sera) in the Norrbotten area of Sweden-were studied. Sera were assayed for total IgE and specific IgE antibodies to relevant allergens. RESULTS: The mean total IgE among wheezing children was higher in New Zealand than Sweden (218 IU/mL vs 65.2 IU/mL; P < .001). In addition, the prevalence of high titer specific IgE antibody (> or =50 IU/mL) was greater among the wheezing children in New Zealand compared with Sweden (35.7% vs 13.0%; P < .001). Specific IgE antibody to mite in New Zealand was significantly related to high total IgE (> or =200 IU/mL; r = 0.47; P < .001), whereas the IgE antibody response to cat allergens did not make a significant contribution to high total IgE in either country. CONCLUSION: The quantity of IgE antibody produced to dust mite provides a possible explanation for the higher total IgE levels found in children in New Zealand and may help to explain the differences in prevalence and severity of asthma between these 2 countries. CLINICAL IMPLICATIONS: Specific IgE antibody responses to dust mite and cat allergens may contribute differently to total serum IgE and to the prevalence of allergic disease.     

House dust mite and cockroach exposure are strong risk factors for positive allergy skin test responses in the Childhood Asthma Management Program

BACKGROUND: Children with asthma have a high prevalence of environmental allergies, especially to indoor allergens. The relationships of exposure to indoor allergens (dust mites, cat, dog, cockroach, and molds) and other host factors to allergy sensitization have not been evaluated simultaneously in a large cohort. OBJECTIVES: We studied 1041 children aged 5 to 12 years with mild-to-moderate asthma to determine risk factors associated with having positive allergy skin test responses to indoor allergens. Also, we described, compared, and contrasted 6 allergens in the home environments of these children from 8 North American cities. METHODS: Data were used from baseline visits of the Childhood Asthma Management Program. Patients' sensitivities to house dust mites (Dermatophagoides farinae and Dermatophagoides pteronyssinus), cats, dogs, cockroaches, and molds were examined for relationships to demographic variables, home dust allergen exposures, number of other positive allergy skin test responses, total serum IgE levels, and smoking in the home. RESULTS: San Diego (78.5%) and Toronto (59.3%) had the topmost percentages of homes with moderate-to-high house dust mite levels. Boston (21.5%), St Louis (16.3%), and Baltimore (13.4%) had the highest percentages of homes with detectable levels of cockroach allergen. For house dust mites, the higher the level of allergen exposure, the more likely patients were to have positive allergy skin test responses, with relative odds of 9.0 (95% confidence interval, 5.4-15.1) for those exposed to high mite levels (>10.0 microg/g dust) relative to those unexposed. Even exposure to low levels of mite allergen (0.020-2.0 microg/g) was found to be a significant risk factor for sensitization. For cockroach allergen, those with detectable home exposure were more likely to have positive skin test responses (relative odds, 2.2; 95% confidence interval, 1.3-3.8) than those with undetectable exposure. In contrast, levels of exposure to cat, dog, and mold allergens were not related to sensitization rates. For cat allergen, this may reflect lower rates of cat ownership among highly sensitized subjects. Furthermore, the number of allergy skin test responses that were positive, excluding the test for the outcome of interest for each model, and total serum IgE levels were strong independent predictors of sensitization. CONCLUSIONS: Levels of exposure determined by house dust analysis are important determinants of sensitization for dust mite and cockroach allergen. This relationship was not demonstrable for cat, dog, or mold allergens, possibly because of confounding factors. For all allergens studied, the degree of atopy, determined by the total number of positive skin test responses or by total serum IgE levels, is an important contributing risk factor for sensitization.     

Exposure and sensitization in infants and children

The complex relationship between allergen exposure, atopic sensitization and asthma in individuals and in populations has recently been a subject of controversy. A number of studies have demonstrated that allergen exposure in sensitized asthmatic individuals increases the severity of disease. A simple dose-response relationship between mite allergen exposure and specific sensitization in infants and children has been confirmed. However, the concept that there is a direct relationship between allergen exposure and the initiation of asthma has been challenged. The relationship between allergen exposure and subsequent disease development is complex, and is confounded by a number of important factors. Populations and individuals are exposed to a mixture of several allergens, irritants and pollutants, and we know very little about the impact of these mixtures and their possible synergistic effect. The dose-response relationship between allergen exposure and allergic disease may not be linear, and may be different for different allergens. For example, a protective effect of cat ownership on sensitization and allergic disease has been reported, raising the question of whether the dose-response relationship between exposure and sensitization may be different for cat compared with mite allergen. It has been suggested that many children who are exposed to a high level of cat allergen make a modified T helper type 2 response, characterized by the presence of IgG4 antibody to cat proteins without becoming allergic (i.e. no IgE response), which could be regarded as a form of tolerance. This could explain a decreased risk of asthma in children living in homes with cats, without invoking a concept of a shift in the balance of T helper types 1 and 2 responses. Cat allergen is ubiquitous, and passive exposure (e.g. home without cats and public places) may induce specific IgE responses in non-cat owners, whereas those exposed to very high levels of cat allergen may initially mount an IgE response, which may be replaced by a modified T helper type 2 response (tolerance). It is likely that the population susceptibility to allergic sensitization and also end-organ responsiveness has altered, and allergen exposure may still be important in initiating disease in an increasingly susceptible population, although the pattern may differ for different allergens.     

Current mite,cat, and dog allergen exposure,pet ownership,and sensitization to inhalant allergens in adults

BACKGROUND: Simultaneous exposure to more than one allergen might modify the effect of individual allergens. OBJECTIVE: The purpose of this study was to investigate the effect of current exposures to mite, cat, and dog allergen and pet ownership on sensitization in adults. METHODS: Questionnaires, skin tests, and home visits (Der p 1, Fel d 1, and Can f 1, ELISA; mattresses, living room floors) were performed in 2502 adults. Allergen exposure was treated as a continuous variable and divided into quartiles. To investigate the interaction between allergens, quartiles for 3 allergens were added, creating arbitrary combined exposure categories. RESULTS: In the univariate analysis, mite sensitization was associated with Der p 1 in mattresses (odds ratio [OR], 1.10; 95% CI, 1.01 to 1.19; P =.03) and with Can f 1 in living room floors (OR, 1.08; 95% CI, 1.00 to 1.17; P =.05). In a multivariate regression analysis, Der p 1 in mattresses remained an independent associate of mite sensitization (OR, 1.12; 95% CI, 1.02 to 1.23; P =.03) and pollen sensitization (OR, 1.23; 95% CI, 1.11 to 1.36; P =.0001). The proportion of subjects sensitized to mite increased significantly with the increasing combined exposure categories (P <.0001). The highest prevalence of sensitization to cat and dog was in the medium combined exposure categories. Cat ownership was associated with a reduced prevalence of sensitization to cats (P =.002) and a reduced prevalence of sensitization to dog (P =.003) but had no effect on sensitization to mite and pollen. CONCLUSIONS: Sensitization to dust mites increased with the increasing combined exposure. Cat ownership was associated with a lower prevalence of sensitization to cat and dog but not to mite and grass pollen.     

Association between severity of atopic eczema and degree of sensitization to aeroallergens in schoolchildren

BACKGROUND: A subgroup of patients with atopic eczema exhibits aggravation through contact with aeroallergens. Little is known from population-based studies, however, about the association between the severity of eczematous skin disease and the degree of aeroallergen sensitization. OBJECTIVE: We sought to investigate the relationship between IgE-mediated allergic sensitization to aeroallergens and severity of atopic eczema in schoolchildren. METHODS: A nested case-control analysis on atopic eczema was performed on the basis of a cross-sectional study of 2201 East German schoolchildren aged 5 to 14 years. Atopic eczema and its severity was identified by dermatologic examination. Total and allergen-specific IgE antibodies to grass and birch pollen, Cladosporium herbarum, Dermatophagoides pteronyssinus, and cat epithelium in serum were determined, and additional information was obtained by means of standardized questionnaire. RESULTS: The overall prevalence of actual atopic eczema was 2.5%. Thirty-seven percent of the children were sensitized to at least one allergen. Children with atopic eczema were significantly more often sensitized than those without skin disease (75.0% vs 36.3%; odds ratio, 5.27; 95% confidence interval, 2.54-11.15). This was observed for each single allergen. The prevalence of atopic eczema increased significantly with increasing RAST class (chi(2) trend test for each allergen, P <.0001). Also, the prevalence of sensitization increased with the severity of the disease (chi(2) trend test for each allergen, P <.0001). This association was pronounced for house dust mite and cat allergen. Multiple linear regression analyses showed significant associations between the severity score of atopic eczema and concentrations of allergen-specific IgE to dust mite (P =.032) and cat (P =.014) allergens after adjustment for sex, age, location, and parental predisposition. CONCLUSIONS: The degree of sensitization is directly associated with the severity of atopic eczema. We speculate that early epicutaneous sensitization to aeroallergens may be enhanced by damage of the skin barrier function. The specific IgE response seems to contribute to the severity of the disease in a dose-dependent fashion.     

Relevance of allergens from cats and dogs to asthma in the northernmost province of Sweden: Schools as a major site of exposure

BACKGROUND: The prevalence of asthma in the northernmost region of Sweden has been estimated at 6% to 8% in spite of the very dry climate. The causes of the increase in asthma are not clear, but conditions are unfavorable for dust mite growth, and domestic animals are thought to be the primary source of indoor allergens. OBJECTIVES: We sought to investigate the relationship between asthma, exposure, and sensitization in Northern Sweden, with a focus on the role of schools. METHODS: Serum was collected from 110 asthmatic children, 55 children with symptoms of asthma but no established diagnosis, and 63 control children (age, 7 and 8 years). Total IgE and specific IgE to 7 allergens were measured. Dust samples were collected from the classrooms of 7- and 8-year-old children in 22 schools from Kiruna and Lulea, Sweden. For comparison, dust was also collected from 24 homes in Kiruna and 2 schools in Virginia in the United States. RESULTS: Serum IgE antibody assays on 165 children with respiratory symptoms confirmed that there was a high degree of sensitization to cat, dog, and birch in Northern Sweden. Cat and dog allergens were present in almost all of the school samples in Sweden. By contrast, dust mite and cockroach allergens were generally unmeasurable. The highest levels of cat and dog allergens were found in samples from desks and chairs. Cat and dog allergen levels in the schools were comparable with but higher than those in the homes without pets. The schools in Virginia had similar allergen levels, except that samples from this humid region also had significant mite allergen. CONCLUSIONS: In this climate the primary sensitization associated with asthma is to cat dander and dog dander but also to birch pollen. Mite and cockroach allergens were not present in the dust samples, and sensitization to these allergens was not significant. The schools appear to be a major site of exposure to cat and dog allergens. These results are relevant both to an understanding of the reasons for the increase in asthma in this region and to any proposal to reduce exposure to allergens.     

Allergen sensitization of asthmatic and nonasthmatic schoolchildren in Costa Rica

The prevalence of asthma among schoolchildren in Costa Rica is very high -at the level of 20-30% - and the reason is still unknown. A group of children from our previous epidemiologic study was randomly selected in order to establish the relation between asthma symptoms and allergy sensitization to common allergens. Serum samples from ciiildren with and without asthma were analyzed for the presence of IgE antibodies to 36 different allergens, for the presence of IgE antibodies to a pool of 10 common allergens, and for total serum IgE. The most prevalent IgE antibodies were those to mite, cockroach, dog, and house-dust allergens with MAST pipettes for the serologic measurements. Positive reactions to house dust, mite, cat, and the two molds (Aiternaria and Ciadosporium), and food allergens such as egg white, peanut, and shellfish were significantly more prevalent among the asthmatics than the nonasthmatics. Sensitization was equally prevalent at different ages, but the house-dust, mite, cat, dog, cockroach, Aiternaria, and egg-white allergens had sensitized boys more often than girls (P<0.01). The result of the analysis of IgE antibodies to a pool of 10 common allergens by Phadiatop supported the MAST pipette results, showing allergen sensitization in 57.7% of the asthmatic children and 42.3% in the nonasthmatic group. The concentration of IgE was significantly higher among the asthmatic children (372.2 kU/1) than among the nonasthmatic children (249.1 kU/1) (P < 0.00001). Parasitic infestations were not examined i n this study, but in most of Costa Rica these have largely been eliminated and could not explain the high total IgE levels. Our data indicate that the very high prevalence of bronchial asthma in Costa Rican schoolchildren can be related to sensitization, especially to airborne indoor allergens such as those of mites, cockroaches, and dogs.     

Association of recurrent wheezing with sensitivity to cockroach allergen in inner-city children.

BACKGROUND: There are numerous data that show a strong relationship between early exposure and sensitization to indoor allergens and the development of asthma and persistent wheezing in children. Most studies, however, have only examined the prevalence of allergy in children who have been identified as having asthma. OBJECTIVE: To assess the prevalence of positive skin test results to common inhaled allergens and possible association with wheezing in inner-city children being seen in a general pediatric clinic. METHODS: Skin testing to common aeroallergens was performed by the prick-puncture method. Demographic and clinical data were collected. RESULTS: Seventy-five children aged 2 months to 10 years were evaluated. A total of 37% of the children had a positive skin test result to at least one allergen; 29% of the children were sensitive to dust mite, 15% to cockroach, 9% to cat, 7% to mold, 4% to grass, 3% to ragweed, and 1% to dog. Seven (64%) of 11 children with positive skin test results to cockroach had a history of wheezing compared with 21 (33%) of 64 with negative skin test results to cockroach (P = .05). CONCLUSIONS: Our results indicate that in a population of inner-city children not previously identified as atopic, more than a third showed sensitivity to at least one allergen. Although dust mite was the most common allergen to which the children were sensitized, cockroach sensitivity was the only allergen that correlated significantly with previous episodes of wheezing.     

Quantitative measurement of IgE antibodies to purified allergens using streptavidin linked to a high-capacity solid phase

BACKGROUND: Commercially available assays for IgE antibody provide results in international units per milliliter for many allergen extracts, but this is not easily achieved with purified or novel allergens. OBJECTIVE: To develop assays for IgE antibody suitable for purified or novel allergens by using a commercially available immunosorbent. METHODS: Streptavidin coupled to a high-capacity immunosorbent (CAP) was used to bind biotinylated purified allergens from mite (Der p 1 and Der p 2), cat (Fel d 1), and dog (Can f 1). Assays for IgE antibody to these allergens were performed on sera from children (asthma and control) as well as adults with atopic dermatitis. RESULTS: The results were validated by serial dilution of sera with high and low levels of IgE antibody and were quantitated in international units per milliliter by using a standard curve. Values for IgE antibody to Der p 1, Der p 2, and Fel d 1 correlated with values obtained with the allergen extracts (r2 = 0.80, 0.84, and 0.95, respectively; P < .001 in each case). Furthermore, the values for IgE antibody in sera from children with high exposure to mite and cat allergens demonstrated 10-fold higher levels of IgE antibody to Der p 1 and Der p 2 than to Fel d 1 (P < .001). CONCLUSION: The streptavidin immunosorbent technique provides a new method for quantifying IgE antibody to purified proteins. The results provide evidence about the high quantities of IgE antibody to purified inhalant allergens in patients with atopic dermatitis. In addition, the results demonstrate major differences in IgE antibodies specific for mite and cat allergens among children with high exposure to both allergens.     

Do levels of immunoglobulin G antibodies to foods predict the development of immunoglobulin E antibodies to cat,dog and/or mite?

BACKGROUND: In children at high risk of inhalation allergy, food sensitization is associated with an increased risk for sensitization to inhalant allergens. Furthermore, this association was also found in a cross-sectional study. OBJECTIVE: To examine in a prospective study, whether levels of IgG to foods (i.e. mixture of wheat and rice, mixture of soy bean and peanut, egg white, cow's milk, meat, orange and potato) indicate an increased risk for the future development of IgE antibodies to inhalant allergens in a low-risk population and whether they can be used as predictors of the subsequent development of IgE antibodies in young, initially IgE-negative children. METHODS: Coughing children, aged 1-5, visiting their GPs, were tested for IgE antibodies to mite, dog and cat (RAST) and IgG (ELISA) to foods. All IgE-negative children were retested for IgE antibodies after two years. The IgG results (66 percentiles) of the first blood sample were compared to the RAST-scores of the second blood sample. RESULTS: After two years, 51 out of 397 (12.8%) originally IgE-negative children, had become IgE-positive for cat, dog and/or mite. An increased IgG antibody level to wheat-rice (OR = 2.2) and to orange (OR = 2.0) indicated an increased risk of developing IgE to cat, dog or mite allergens. In addition to IgG to a mixture of wheat-rice and orange; total IgE, breastfeeding, eczema as a baby and age were the most important predictors for the subsequent development of IgE to inhalant allergens. DISCUSSION: An increased IgG antibody level to a mixture of wheat-rice or orange, indicates an increased risk of developing IgE to cat, dog or mite allergens. This indicates that excessive activity of the mucosal immune system is present before IgE antibodies to airborne allergens can be demonstrated. Nevertheless, IgG to foods is not very helpful (with a positive predictive value of 16.5%, and negative predictive value of 90.6%) in identifying individual children at risk in clinical practice. However, besides other risk factors, IgG to wheat-rice and to orange could be useful as a screening test for studies in the early identification, i.e. before IgE antibodies can be detected, of children with an increased risk of developing IgE antibodies in the future.     

Higher incidence of Dermatophagoides pteronyssinus allergy in children of Taipei city than in children of rural areas.

BACKGROUND AND PURPOSE: House dust mites are the most common cause of sensitization in wheezing children in most parts of the world. The aim of this study was to investigate prevalence of sensitization and the levels of specific immunoglobulin E (IgE) to Dermatophagoides pteronyssinus (Der p) in wheezing children in Taipei city and central rural Taiwan. METHODS: A total of 3546 children were enrolled in this study. Children were grouped into those living in Taipei city (n = 1340) and those residing in the rural part of central Taiwan (2206). The prevalence of sensitization and level of specific IgE antibody to Der p and cockroach were analyzed by age and geographic area. RESULTS: The results showed significantly higher sensitization rates and mean specific IgE levels to Der p with increasing age of patients in both Taipei city and rural central Taiwan. In addition, children from Taipei city had a significantly higher average sensitization rate of Der p than rural children (p<0.05). The proportion of children sensitized to cockroach increased with age both in Taipei city and central rural Taiwan, but the specific IgE levels to cockroach were not statistically different between the 2 groups (p=0.061). CONCLUSIONS: Sensitivity to aeroallergens varies with age and with geographical location (city vs rural) in asthmatic children. Circulating IgE antibodies against Der p were common at all ages. Cockroach allergen is also associated with recurrent wheezing in Taiwan. Avoidance of indoor aeroallergens such as Der p and cockroach allergen should be an important component in plans for the management of recurrent wheezing.     

Differences in both prevalence and titre of specific immunoglobulin E among children with asthma in affluent and poor communities within a large town in Ghana

Background Reports from several African countries have noted an increasing prevalence of asthma in areas of extensive urbanization. Objective To investigate the relevance of allergen‐specific sensitization and body mass index (BMI) to asthma/wheezing and exercise‐induced bronchospasm (EIB) among children from affluent and poorer communities within a large town in Ghana. Methods Children with physician‐diagnosed asthma and/or current wheezing aged 9–16 years (n=99; cases) from three schools with differing socio‐economic backgrounds [urban affluent (UA), urban poor (UP) or suburban/rural (SR)] were recruited from a cross‐sectional study (n=1848) in Kumasi, Ghana, and matched according to age, sex and area of residence with non‐asthmatic/non‐wheezy controls. We assayed sera for IgE antibodies to mite, cat, dog, cockroach, Ascaris and galactose‐α‐1,3‐galactose. Results Children from the UA school had the lowest total serum IgE. However, cases from the UA school had a higher prevalence and mean titre of sIgE to mite (71.4%, 21.2 IU/mL) when compared with controls (14.3%, 0.8 IU/mL) or cases from UP (30%, 0.8 IU/mL) and SR community (47.8%, 1.6 IU/mL). While similar findings were observed with EIB in the whole population, among cases there was no difference in IgE antibody prevalence or titre between children with or without EIB. BMI was higher among UA children with and without asthma; in UP and SR communities, children with EIB (n=14) had a significantly higher BMI compared with children with asthma/wheezing without EIB (n=38) (18.2 vs. 16.4, respectively, P<0.01). Conclusions and Clinical Relevance In the relatively affluent school, asthma/wheezing and EIB were associated with high titre IgE antibodies to mite, decreased total IgE, and increased BMI. This contrasted with children in the urban poor school and suggests that changes relevant to a Western model of childhood asthma can occur within a short geographical distance within a large city in Africa. Cite this as: W. Stevens, E. Addo‐Yobo, J. Roper, A. Woodcock, H. James, T. Platts‐Mills and A. Custovic, Clinical & Experimental Allergy, 2011 (41) 1587–1594.     

Serum IgG and IgG4 antibodies to Fel d 1 among children exposed to 20 microg Fel d 1 at home: relevance of a nonallergic modified Th2 response

Exposure to foreign antigens is an essential element of all immune responses, including allergic sensitization. For some allergens (e.g. mite and cockroach), the prevalence of sensitization is directly correlated with exposure. However, for allergens derived from domestic animals, several studies have suggested that children with a cat in the home have a decreased risk of sensitization and asthma. We have now shown that many children exposed to greater than 20 microg of Fel d 1/g of dust at home made an IgG and IgG4 antibody response to Fel d 1 without IgE antibody. This modified Th2 response is not associated with symptoms and should be regarded as a form of immunological tolerance. The fact that the dose-response relationship between cat exposure and sensitization is bell shaped, while that for mite exposure and sensitization is linear, is highly relevant to understanding the role of allergens in the increase in allergic disease.     

Number of allergens to be tested to assess allergenic sensitization in epidemiologic studies: results of the European Community Respiratory Health Survey I

BACKGROUND: Many clinical and epidemiological studies have measured the prevalence of IgE sensitization using skin tests and/or serum-specific IgE. Most of them have been done in only one country using a battery of selected allergens relevant to that country. In multi-centre studies, the number of tested allergens is often limited by the cost. It is therefore difficult to compare prevalence of sensitized subjects between studies. OBJECTIVE: To define the number and the type of allergen that should be tested in order to characterize a person as sensitized. METHOD: Subjects were selected from the European Community Respiratory Health Survey I. All subjects underwent skin prick tests to nine of the most common allergens. In addition, two local allergens were tested in some centres. RESULT: Using nine allergens, 35.6% of the 11 355 subjects were sensitized. The prevalence of sensitization increased with the number of tested allergens. Seven allergens enabled the identification of almost all sensitized subjects, adding another one inducing, in most countries, an increase of prevalence under 0.5%. Adding one local allergen to the battery of tests increased the overall estimated prevalence by only 1%. This increase was not seen in Ireland and was less marked in the United Kingdom (0.3%) but was greater in France (2.6%), Australia (2.5%) and Belgium (1.9%). CONCLUSION: Seven selected allergens (Dermatophagoides pteronyssinus, cat, grass, birch, olive pollen, Alternaria and Cladosporium) allow the identification of almost all sensitized subjects in epidemiologic studies. Inclusion of local allergen should be considered in a standard panel for international studies.     

Atopy in childhood. I. Gender and allergen related risks for development of hay fever and asthma

Reasons for the gender differences in prevalence rates for asthma remain unclear. We have examined the relationships between allergen skin-test reactions and diagnoses of hay fever and asthma in New Zealand boys and girls examined at the age of 13 years. Information on current and past wheezing, diagnosed asthma, and hay fever was obtained for 662 subjects (341 boys) of a birth cohort followed longitudinally to the age of 13 years, using a physician-administered questionnaire. Atopic status was determined by skin-prick tests to 11 common allergens. The proportion of 13-year-old boys with current asthma was 1.6 times higher and of ever-diagnosed asthma 1.4 times higher than in girls, but the prevalence of recurrent wheeze (> or = three episodes per year) not diagnosed as asthma, or of hay fever, was not significantly different between the sexes. The prevalence of diagnosed asthma increased with increasing numbers of positive skin tests, but hay fever without asthma was little affected above one positive skin-test. Boys had a greater prevalence of any positive skin-test (50.1% vs 37.1%), two or more positive tests (29.3% vs 21.8%), and responses to house dust mite (34.0% vs 23.1%) and cat (14.7% vs 11.2%). Gender differences for asthma became insignificant when adjusted for skin-test responsiveness to house dust mite and/or cat. The proportion of children with diagnosed asthma increased with increasing size of weals to house dust mite and cat dander. Gender differences in allergen sensitivities partly explain the gender differences in diagnosed asthma in children. In both sexes, risk of asthma was primarily associated with sensitization to indoor allergens (house dust mite and cat), and was related to the magnitude of the skin-test response, while the risk of hay fever was primarily associated with grass pollen sensitivity.     

Allergic sensitization to indoor and outdoor allergens and relevance to bronchial hyperresponsiveness in younger and older subjects

BACKGROUND: Most previous epidemiological studies on the relationship between allergy and bronchial hyperresponsiveness (BHR) have made no distinction between sensitization to indoor and outdoor allergens. We studied the relationship between specific sensitization to allergen and BHR and further assessed whether this was different in young adults and older subjects. METHODS: Specific IgE to indoor allergens (house dust mite and cat) and outdoor allergens (timothy grass and birch) were measured using the CAP System. BHR was defined as PD20 /= 3). Young adults with multiple sensitization had the highest risk of BHR. Subjects who were exclusively sensitized to pollen did not show increased BHR in both age groups. Total IgE had, independently of sensitization, only a significant dose-response relationship with BHR in the oldest age group. CONCLUSIONS: The association between sensitization and BHR is dependent on the nature of the allergen and the level of specific IgE. Furthermore, this study shows for the first time that total IgE is associated with BHR at older ages, independently of sensitization.     

Endotoxin exposure and atopic sensitization in adult pig farmers

BACKGROUND: Recent studies have reported a low prevalence of atopic sensitization and respiratory allergy in children growing up on farms. OBJECTIVES: We sought to evaluate the dose-response relationship between endotoxin and atopic sensitization in adult farmers and to assess the effect on respiratory health outcomes. METHODS: Data on endotoxin exposure and serum IgE levels were available for 162 pig farmers from a cross-sectional case-control study, with case selection on the basis of respiratory symptoms. Exposure to endotoxin was modeled in detail, and respiratory health effects were assessed during a medical examination. Exploratory analysis was done by using nonparametric modeling and was followed by classical parametric regression. RESULTS: IgE to one or more common allergens was detected in sera from 28 (17%) farmers. The average (geometric mean) total serum IgE levels was 37 IU/mL (geometric SD, 4 IU/mL). A strong inverse relationship was found between endotoxin and sensitization to common allergens for exposures of 75 ng/m 3 or less, with an odds ratio of 0.03 (95% CI, 0.0-0.34) for a 2-fold increase in endotoxin. For endotoxin exposure of greater than 75 ng/m 3 , the association was weak (odds ratio, 1.2 [95% CI, 0.38-3.6]). No association was found between endotoxin exposure and total serum IgE levels. Endotoxin was associated with increased airway hyperresponsiveness to histamine and lower lung function in sensitized farmers, without evidence of a nonlinear relationship. CONCLUSIONS: The prevalence of atopic sensitization in adult pig farmers is low. Endotoxin or related exposures might protect from sensitization, even in an adult working population exposed to high levels of endotoxin, but is a risk factor for increased airway hyperresponsiveness and low lung function.     

Allergic sensitization owing to 'second-hand' cat exposure in schools

BACKGROUND: Environmental allergen loads play an important role in triggering symptoms in atopic individuals. While a number of previous studies have shown that cat allergens (Fel d 1) can be found in school dust samples, no study has provided evidence that public places contribute to increased atopic sensitization rates in children. METHODS: We employed data collected in a health survey of school children living in Germany in order to examine the association between the proportion of class- and schoolmates reporting cat contact and sensitization rates in children. RESULTS: Among 1893 children, 8.7% were sensitized to cats. Those sensitized were 5-7 times more likely to have received an asthma diagnosis or to have reported wheezing. Pupils without regular contact with cats were twice as likely to test positive for major cat allergen when the proportion of schoolmates with cat contact was high. No such relation was observed amongst children reporting regular cat contact. CONCLUSIONS: Our study suggests that allergens in school environments contribute to allergic sensitization and atopic diseases such as asthma. Thus, methods to reduce the allergen load in classrooms should be considered.     

Relationship between aeroallergen and food allergen sensitization in childhood

BACKGROUND: Previous studies measuring the prevalence of allergen sensitization have been relatively small and used small numbers of allergens. To effectively evaluate children with atopic disease, we need an accurate knowledge of which allergens are important. OBJECTIVE: To measure the prevalence of sensitization within a large unselected birth cohort, to examine the associations between sensitization to different allergens and determine whether atopy can be defined by a small panel of allergens. METHODS: The Avon Longitudinal Study of Parents and Children is a population-based birth cohort of 13,638 singletons surviving to 4 weeks of age. The cohort was skin tested at 7 years of age to house dust mite (Dermatophagoides pteronyssinus), grass pollens, cat, peanuts, mixed tree nuts and egg and one of three other panels: animal danders, foods or aeroallergens. Sensitization was defined as a weal diameter of > or =3 mm. The strength of associations between sensitization to different allergens was tested by calculating the odds ratio adjusted for sensitization to D. pteronyssinus and grass pollen and gender. RESULTS: Valid data were obtained from 6412 singletons. Sensitization was most common to aeroallergens: grass pollens (8.5%), D. pteronyssinus (7.8%), cat (4.9%), D. farinae (3.6%), dog (2.7%), horse (1.4%), rabbit (1.4%). Of the foods tested, the most common sensitization was to peanut (1.4%) and mixed tree nuts (1.0%). More than 95% of subjects with sensitization to any of the 29 allergens tested were sensitized to one of grass, D. pteronyssinus or cat allergen. There were strong associations of multiple sensitizations both within and between different allergen classes (pollens, animals, foods, peanut and tree nuts). CONCLUSIONS: Seven-year-old children in the UK are primarily sensitized to aeroallergens, but also to peanuts and tree nuts. There are strong associations between sensitization within allergen groups as well as between allergen groups. Further studies are required to observe whether similar associations are seen with clinical allergy to these allergens.     

Cat allergen level: its determinants and relationship to specific IgE to cat across European centers

BACKGROUND: Cat allergen level in settled house dust and its determinants in Europe are unknown. OBJECTIVE: The aim of this study is to quantify the level of cat allergens in mattress dust, to study its determinants, and to analyze the relationship with cat specific IgE on community level across European centers. METHODS: Trained field workers collected dust from approximately 3000 mattresses during home visits in 22 European Community Respiratory Health Survey II centers. Sieved dust extracts were assayed for cat allergen using a mAb ELISA assay. RESULTS: The overall geometric mean cat allergen was 0.94 microg/g, ranging from 0.12 microg/g in Huelva, Spain, to 3.76 microg/g in Antwerp, Belgium. Current cat owners' homes showed substantially higher levels than past cat owners' and never cat owners' homes (geometric mean and 95% CI, 61.4 microg/g [48.4-77.9] vs 1.37 microg/g [0.97-1.9] vs 0.29 microg/g [0.27-0.31]). Community prevalence of cat ownership was moderately correlated with cat allergen levels in noncat owners (r(s) = 0.50), but not for past or current cat owners. The multilevel model identified community prevalence of cat keeping as the only statistically significant determinant of mattress cat allergen levels for noncat owners. However, averaged cat allergen levels per center were not related to community prevalence of detectable specific IgE to cat. CONCLUSION: Not having a cat in the home is associated with substantially lower Fel d 1 concentration, but does not protect against high Fel d 1 exposure in communities where cat ownership is common. CLINICAL IMPLICATIONS: People (including patients with cat allergy) who do not own cats may be exposed to high levels of cat allergen in their home, particularly if they live in communities with high levels of cat ownership.