Longitudinal study on the relationship between cat allergen and endotoxin exposure, sensitization, cat-specific IgG and development of asthma in childhood--report of the German Multicentre Allergy Study (MAS 90)

BACKGROUND: Controversial data have emerged regarding the question whether cat exposure in childhood favours or decreases the risk of sensitization and allergic airway disease. In a prospective birth-cohort study, we assessed the association between longitudinal cat allergen exposure, sensitization (immunoglobulin E, IgE), IgG antibody (ab) levels to cat and the development of asthma in children up to the age of 10 years. METHODS: Of 1314 newborn infants enrolled in five German cities in 1990, follow-up data at age 10 years were available for 750 children. Assessments included yearly measurements of specific serum IgE to cat and at age 6 and 18 months, 3, 4 and 10 years measurement of cat allergen Fel d 1 in house dust samples. Additionally, Fel d 1-specific IgG ab were determined in 378 serum samples of 207 children. Endotoxin exposure in mattress dust was measured in a subgroup of 153 children at age 10 years. From age 4 years on, International Study of Asthma and Allergy in Childhood (ISAAC) questionnaires were completed yearly in order to assess the prevalence of wheeze and asthma. RESULTS: Serum IgG-levels to cat showed a large variation, however, intraindividually values showed rather constant concentration over a longer time period. The IgG levels at school-age correlated with cat allergen exposure during the first 2 years of life. Specific IgE to cat was clearly associated with wheeze ever, current wheeze and bronchial hyperresponsiveness (BHR), this was also observed for children with specific IgE ab to cat (>0.35 kU/l) plus IgG levels above 125 U/ml. A large percentage of very highly exposed children showed high IgG but no IgE responses to cat, however, not all highly exposed children were found to be protected from sensitization. Children with IgG but without IgE ab to cat showed the lowest prevalence of wheeze ever and current wheeze despite high cat allergen exposure, however, this trend did not achieve significance. While homes of cat owners showed higher Fel d 1 concentrations than homes without cats, homes of cat owners were not found to have higher endotoxin levels in carpet dust samples than homes without cats. CONCLUSIONS: We could confirm that high cat allergen exposure in a cohort with lower community prevalence of cats is associated with higher serum IgG and IgE levels to cat in schoolchildren. Sensitization to cat allergen (IgE) is a risk factor for childhood asthma. While exposure to cat allergen during infancy is associated with sensitization (IgE), only in the very highly exposed children the likelihood of sensitization (IgE) is decreased and high IgG levels to cat without IgE were associated with low risk of wheeze. However, cat-specific IgG ab levels did not protect children with IgE-mediated sensitization from wheeze.     

Relationship of house-dust mite allergen exposure in children's bedrooms in infancy to bronchial hyperresponsiveness and asthma diagnosis by age 6 to 7.

BACKGROUND: Several studies have suggested that exposure to house-dust mite (HDM) allergen in infancy increases the risk of developing asthma. OBJECTIVE: To determine whether exposure to higher levels of dust mite in infants increased the risk of developing bronchial hyperresponsiveness (BHR) or physician-diagnosed asthma by age 6 to 7 years. METHODS: A health maintenance organization-based cohort of 97 middle class suburban children born from 1987 to 1989 with a high cord blood immunoglobulin E, defined as > or = 0.56 IU/mL, was followed as a part of the Childhood Allergy Study. During the first 2 years of life, monthly bedroom dust samples were collected and analyzed for Der f 1 and Der p 1. Between 6 and 7 years of age, 64 of the original cohort answered a questionnaire used to determine the presence of physician-diagnosed asthma, underwent clinical examination, skin prick testing, and methacholine inhalation challenge. Mann-Whitney tests were used to compare Der f 1 and Der p 1 levels in homes of children with and without BHR, and those with and without physician-diagnosed asthma. RESULTS: In all, 1,421 dust samples were collected and assayed. No significant differences were seen in either the mean, maximum, or minimum dust mite allergen levels in homes of children with versus without BHR, or children with versus without asthma. However, sensitization to HDM was associated with physician-diagnosed asthma (P < 0.05). CONCLUSIONS: When compared with other studies, we were able to more accurately estimate the level of dust mite allergen exposure through repeated sampling over a relatively long period, incorporating seasonal variations. Although HDM sensitization and asthma were concurrently related, we were unable to find any relationship between level of HDM allergen exposure in children's bedrooms in early childhood and development of BHR or physician-diagnosed asthma by age 6 to 7 years.     

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.     

Family history, dust mite exposure in early childhood, and risk for pediatric atopy and asthma

BACKGROUND: Dust mite allergen exposure is considered a major determinant of sensitization to these allergens during childhood and a risk factor for pediatric asthma. OBJECTIVE: By using a birth cohort in a setting with a substantial burden of dust mite allergen, we evaluated exposure and risk for outcomes related to allergy and asthma. METHODS: We collected dust from the bedrooms of 428 children born from 1987 to 1989 and measured Der f 1 and Der p 1 (microg/g dust, combined). Follow-up at 6 to 7 years of age included clinical examination, skin prick testing, specific serum IgE measurement, and methacholine challenge. RESULTS: No overall association was evident for any outcome except bronchial hyperresponsiveness (adjusted odds ratio [OR], 0.62; 95% CI, 0.38-1.00; P <.050; and OR, 0.53; CI, 0.27-1.04; P <.065 for dust mite allergen levels > or =2 microg/g and >10 microg/g, respectively). With a parental history of allergy and asthma, there was an association between a positive dust mite skin test (OR, 2.09; CI, 0.93-4.73; P <.076) and dust mite allergen level >10 microg/g. The inverse was true for children without a parental history. Dust mite exposure of >10 microg/g was associated with a decreased risk of current atopic asthma among children with a parental history (OR, 0.39; CI, 0.05-3.13; P <.376), but with increased risk if without a parental history (OR, 1.52; CI, 0.22-10.6; P <.673). CONCLUSION: Parental history is an important independent variable in the relationship between early dust mite exposure and atopic outcomes. Increased exposure during infancy is associated with a higher risk for sensitization in the presence of a positive parental history, but is protective among children of parents without a history of atopic disease.     

Three-year outcomes of dietary fatty acid modification and house dust mite reduction in the Childhood Asthma Prevention Study

BACKGROUND: Two factors thought to influence the risk of asthma are the promoting effect of sensitization to house dust mites and the preventive effect of increased omega-3 fatty acids. Although house dust mite allergen avoidance has been used as a preventive strategy in several trials, the effect of omega-3 fatty acid supplementation in the primary prevention of asthma and allergic disease is not known. OBJECTIVE: To measure the effects of dietary supplementation with omega-3 fatty acids and house dust mite allergen avoidance in children with a family history of asthma. METHODS: A total of 616 children at high risk of asthma were enrolled antenatally in a randomized controlled trial, and 526 children remained in the trial at age 3 years. The outcomes were symptoms of allergic disease and allergen sensitization. RESULTS: There was a significant 10.0% (95% CI, 3.7-16.4) reduction in the prevalence of cough in atopic children in the active diet group ( P=.003; number needed to treat, 10) but a negligible 1.1% (95% CI, -7.1 to 9.5) reduction cough among nonatopic children. There was a 7.2% (95% CI, 10.11-14.3) reduction in sensitization to house dust mite in the active allergen avoidance group ( P=.05; number needed to treat, 14). No significant differences in wheeze were found with either intervention. CONCLUSION: These results suggest that our interventions, designed to be used in simple public health campaigns, may have a role in preventing the development of allergic sensitization and airways disease in early childhood. This offers the prospect of reducing allergic disease in later life.     

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.     

Prevention of allergic disease during childhood by allergen avoidance: the Isle of Wight prevention study

BACKGROUND: Early life allergen exposure may increase the risk of childhood allergy, but the protective effect of reduction in allergen exposure remains uncertain. OBJECTIVE: To evaluate the effect of reduction in food and house dust mite (HDM) allergen exposure in infancy in preventing asthma and allergy. METHODS: Infants, at higher risk because of family predisposition, were recruited prenatally and randomized to prophylactic (n = 58) and control (n = 62) groups. Prophylactic group infants were either breast-fed with mother on a low allergen diet or given an extensively hydrolyzed formula. Exposure to HDM was reduced by the use of an acaricide and mattress covers. The control group followed standard advice. Development of allergic diseases and sensitization to common allergens (atopy) was assessed blindly at ages 1, 2, 4, and 8 years in all 120 children. RESULTS: Repeated measurement analysis, adjusted for all relevant confounding variables, confirmed a preventive effect on asthma: adjusted odds ratio (OR), 0.24; 95% CI, 0.09-0.66; P = .005; atopic dermatitis, OR, 0.23; CI, 0.08-0.64; P = .005; rhinitis, OR, 0.42; CI, 0.19-0.92; P = .03; and atopy, OR, 0.13; CI, 0.05-0.32; P < .001. The protective effect was primarily observed in the subgroup of children with persistent disease (symptoms at all visits) and in those with evidence of allergic sensitization. CONCLUSION: Allergic diseases can be reduced, for at least the first 8 years of life, by combined food and HDM allergen avoidance in infancy. CLINICAL IMPLICATIONS: Strict food and HDM allergen avoidance should be considered for prevention of allergy in high-risk infants.     

Childhood asthma and early life exposure to indoor allergens,endotoxin and β(1,3)‐glucans

Background Divergent results have been reported regarding early life exposure to indoor environmental agents and the risk of asthma and allergic sensitization later in life. Objective To assess whether early exposure to indoor allergens, β(1,3)‐glucans and endotoxin modifies the risk of allergic diseases at 10 years of age. Methods The concentrations of mite, cat and dog allergens, endotoxin and β(1,3)‐glucans were determined in dust from the homes of 260 two‐year‐old children with lung function measured at birth (tidal flow volume loops) in the Environment and Childhood Asthma study in Oslo. At 10 years, the health status was assessed in a follow‐up study including a structured interview of the parents and an extended clinical examination. Results Cat and dog keeping at 2 years of age was reported in 6.5% and 5.5% of the families, respectively. Mite allergens were detected in only 4/260 dust samples. The adjusted odds ratio for asthma at age 10 was 1.20 (95% confidence interval: 1.01–1.43) and 1.22 (1.02–1.46) for bronchial hyperresponsiveness (BHR) per 10 μg/g dust increase in cat allergen exposure at 2 years of age. No association was seen with allergic sensitization. Moreover, endotoxin and β(1,3)‐glucan exposure did not modify the risk of asthma or allergic sensitization. None of the measured environmental factors were associated with lung function at 10 years of age or a relative change in lung function from birth. Conclusion In a community with a low prevalence of pet keeping and low mite allergen levels, exposure to cat allergens early in life increased the risk of late childhood asthma and BHR, but not the risk of allergic sensitization. No risk modification was seen for dog allergens, endotoxin and β(1,3)‐glucans. Cite this as: R. J. Bertelsen, K. C. Lødrup CarlsenK.‐H. Carlsen, B. Granum, G. Doekes, G. Håland, P. Mowinckel and M. Løvik, Clinical & Experimental Allergy, 2010 (40) 307– 316.     

Exposure to dust mite allergen and endotoxin in early life and asthma and atopy in childhood

BACKGROUND: There has been no longitudinal study of the relation between concurrent exposure to dust mite allergen and endotoxin in early life and asthma and atopy at school age. OBJECTIVES: To examine the relation between exposure to dust mite allergen and endotoxin at age 2 to 3 months and asthma, wheeze, and atopy in high-risk children. METHODS: Birth cohort study of 440 children with parental history of atopy in the Boston metropolitan area. RESULTS: In multivariate analyses, early exposure to high levels of dust mite allergen (> or =10 microg/g) was associated with increased risks of asthma at age 7 years (odds ratio [OR], 3.0; 95% CI, 1.1-7.9) and late-onset wheeze (OR, 5.0; 95% CI, 1.5-16.4). Exposure to endotoxin levels above the lowest quartile at age 2 to 3 months was associated with reduced odds of atopy at school age (OR, 0.5; 95% CI, 0.2-0.9). In contrast with its inverse association with atopy, endotoxin exposure in early life was associated with an increased risk of any wheeze between ages 1 and 7 years that did not change significantly with time (hazard ratio for each quartile increment in endotoxin levels, 1.23; 95% CI, 1.07-1.43). CONCLUSION: Among children at risk of atopy, early exposure to high levels of dust mite allergen is associated with increased risks of asthma and late-onset wheeze. In these children, endotoxin exposure is associated with a reduced risk of atopy but an increased risk of wheeze. CLINICAL IMPLICATIONS: Early endotoxin exposure may be a protective factor against atopy but a risk factor for wheeze in high-risk children.     

The PASTURE project: EU support for the improvement of knowledge about risk factors and preventive factors for atopy in Europe

Since January 2002, the European Commission is funding a large project, 'Protection against Allergy--Study in Rural Environments' (PASTURE; contract no. QLK4-2001-00250), under the Fifth Framework Program in the field of epidemiology of allergic diseases. The aim of this paper was to describe the background and design as well as the aims of the project. Asthma and allergic disorders are a major public health problem in many Western countries. The aetiology of asthma and allergic disease remains poorly understood despite considerable research. Epidemiology has the potential to add greatly to the understanding by elucidating the risk factors for asthma and allergic disease and thereby suggesting productive avenues for research into causation and prevention. Several risk factors for the development of asthma and atopic disease in children such as passive smoke exposure during pregnancy and infancy, low birth weight or high body mass index later in life have been described. Furthermore, there is consistent evidence that the prevalence of atopy increases with higher socio-economic status. Levels of air pollution such as ozone, NO2, SO2 and particles are likely to provoke acute exacerbations of pre-existent respiratory disease. Their role in the inception of asthma and allergies remains to be clarified. Allergen exposure has been linked to the development of atopic sensitization to that particular allergen in children as well as in adults with occupational exposures. Exposure to house dust mite or cat allergen is, however, unlikely to contribute to the development of childhood asthma. In turn, pet keeping in the first year of life, particularly, dog keeping, has been inversely related to the development of wheeze and atopic illnesses. Several prospective birth cohort studies found a decreased prevalence of atopic disease in children having daily contact to pets, in particular to cats and dogs, during early infancy. The protective effect might be attributable to allergen or other exposures associated with pet ownership, but may also in part be because of the removal of pets in families with sensitized or symptomatic children or in families with a positive history for atopy at the time the child was born.     

Asthma and sensitization in a community with low indoor allergen levels and low pet-keeping frequency

BACKGROUND: Little is known about causes of asthma and sensitization in desert countries. OBJECTIVE: To investigate risk factors associated with asthma and sensitization in Kuwait. METHODS: One hundred sixty children (9-16 years) with physician-diagnosed asthma were recruited and matched (age, sex) with 303 healthy controls. Risk factors were assessed by questionnaires, determination of sensitization status (skin tests and IgE), and home allergen exposure (mite, cat, dog, cockroach; ELISA). RESULTS: Home allergen levels and frequency of pet ownership were very low (cat, 4.1%; dog, 1.5%). The risk of cat sensitization increased significantly among cat owners (odds ratio [OR], 3.53; 95% CI, 1.33-9.41; P = .01), and in children with reported contact with cats during the first year of life (OR, 2.60; 95% CI, 1.17-5.80; P = .019). In the multivariate analysis, maternal atopy (OR, 1.77; 95% CI, 1.13-2.75; P = .01) and cat ownership (OR, 3.32; 95% CI, 1.19-9.25; P = .02) remained significant associates of cat sensitization. Current dog ownership significantly increased the risk of sensitization to dog (OR, 6.05; 95% CI, 1.33-27.54; P = .02). In the multivariate analysis, dog ownership remained the only significant associate of dog sensitization (OR, 6.02; 95% CI, 1.30-27.96; P = .02). Sensitization to Alternaria was the strongest independent associate of the asthma group. Family history of asthma, history of whooping cough, current cat ownership, and breast-feeding <2 months were other significant and independent risk factors for asthma. CONCLUSIONS: Pet ownership markedly increased the risk of sensitization to pets. Despite low allergen exposure, the pattern of childhood asthma in Kuwait follows that described in Western communities (strong association with sensitization).     

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.     

Effects of pets on asthma development up to 8 years of age: the PIAMA study

Background:  Recall bias may provide discrepant relationships of pet exposure with sensitization and asthma development. We studied prospectively effects of pets at home on development of sensitization, asthma and respiratory symptoms from birth up to age 8 years.
Methods:  Event history analysis was performed on annually registered data of 2951 children, participating in the PIAMA birth cohort study.
Results:  Children with a cat or dog at home at 3 months of age had a significantly lower prevalence of sensitization to inhalant allergens at age 8, but not of asthma. A cat decreased the risk of house dust mite sensitization at age 8 [odds ratio (OR) = 0.68, 95% confidence interval (CI) 0.49–0.95], a dog of pollen sensitization (OR = 0.49, 95% CI: 0.29–0.83). A cat or dog at home did not significantly affect asthma incidence in each subsequent year. From 2 years of age onwards, the incidence of wheeze (OR = 1.52, 95% CI: 1.12–2.05) and a dry cough at night (OR = 1.28, 95% CI: 1.05–1.57) was higher in children with a dog, whereas removal of a dog increased the risk of developing asthma symptoms. Comparing analyses using prospectively and retrospectively collected data on diagnosed asthma showed important recall bias.
Conclusions:  Our prospective study shows a protective effect of early presence of pets at home on sensitization to inhalant allergens, but no prevention of asthma development. Furthermore, children with pets had more frequent transient or intermittent asthma symptoms. Parental report of asthma by recall may provide spurious results of these associations.     

Sensitivity to common allergens: relation to respiratory symptoms and bronchial hyper-responsiveness in children from three different climatic areas of Australia

In order to examine further the relation between atopy, as defined by skin-prick tests, and respiratory illness, we studied three populations of schoolchildren aged 8-11 years and living in different climatic areas of New South Wales, Australia. Skin-prick tests were performed using 13 commercial allergen extracts. Respiratory and allergic symptoms were assessed using a self-administered questionnaire to parents and bronchial hyper-responsiveness (BHR) was measured by histamine inhalation test. We defined current asthma as BHR together with symptoms of wheeze in the 12 months prior to study. Children with one or more positive skin weals of greater than or equal to 3 mm had significantly more recent wheeze, hayfever, eczema and BHR than children with smaller weals (P less than 0.001). In each area, 95-97% of all atopic children were sensitized to one of the following seven allergens: house dust, Dermatophagoides farinae, D. pteronyssinus, cat dander, plantain, rye grass, and Alternaria tenuis. Thus, these seven selected allergen extracts and a skin weal of 3 mm could be used to detect clinically relevant atopy in these populations of children. Sensitivity to house dust mite had the strongest independent association with current asthma in all three areas. The associations of other allergen sensitivities with BHR or current asthma were area dependent, indicating the influence of local allergen levels on respiratory illness in children. The potency of house dust mite sensitivity in increasing the risk of children having BHR and current asthma is confirmed.     

Intranasal air sampling in homes: relationships among reservoir allergen concentrations and asthma severity

BACKGROUND: The relationship among inhaled allergen exposure, sensitization, and asthma severity is unknown. OBJECTIVES: To investigate the relationship among personal allergen exposure, reservoir dust allergen concentrations, and physiological measures of asthma severity; to examine the numbers of particles inspired that react with autologous IgE and IgG4. METHODS: A total of 117 patients with asthma wore 5 nasal air samplers (NASs) at home: 1 each for exposure to mite, cat and dog allergens, NAS-IgE, and NAS-IgG4. NASs were processed by HALOgen assay for allergen measurement and incubated with autologous serum for detection of NAS-IgE and NAS-IgG4. Reservoir allergen concentrations were measured by ELISA. Subjects' asthma severity was ascertained by measurement of lung function, exhaled nitric oxide, and nonspecific bronchial reactivity to histamine. RESULTS: Nasal air sampler counts correlated with reservoir concentrations for cat (r=0.31; P=.001) and dog (r=0.20; P=.03) but not mite allergen (r=0.001; P=1.0). There was no significant relationship between sensitization with exposure measured by NAS to any allergen and PD20FEV1 (F[3,60]=1.60; P=.20); however, sensitization with exposure in dust reservoirs had significant effects on PD20FEV1 for any allergen (F[3,59]=3.12; P=.03), cat (F[3,59]=3.77; P=.01), and mite (F[3,59]=2.78; P=.05), but not dog (F[3,59]=1.06; P=.37). We repeated the analysis with separate variables for sensitization and exposure, controlling for the confounders; sensitization but not exposure conferred lower PD20FEV1 values. However, increasing cat allergen exposure was associated with improving bronchial reactivity in not cat-sensitized patients. NAS-IgE and NAS-IgG4 counts bore no relationship to any measure of asthma severity. CONCLUSION: Nasal air samplers confer no advantage over reservoir dust analysis for studies of asthma severity. CLINICAL IMPLICATIONS: In common with other measures of exposure, single nasal air samples do not provide a useful measure of home allergen exposure for the individual patient with allergic asthma.     

Nonlinear relations between house dust mite allergen levels and mite sensitization in farm and nonfarm children

BACKGROUND: Low sensitization rates to common allergens have been observed in farm children, which might be due to high exposure to microbial agents. It is not known how microbial agents modify the association between specific allergen exposure and sensitization. OBJECTIVE: To examine the relations between house dust mite allergen exposure and mite sensitization in farm and nonfarm children and to assess the effects of microbial agents levels on this association. METHODS: Major mite allergens of Dermatophagoides pteronyssinus (Der p 1) and Dermatophagoides farinae (Der f 1), endotoxin, beta(1,3)-glucans and fungal extracellular polysaccharides were measured in mattress dust of 402 children participating in a cross-sectional study in five European countries. Mite allergen (Der p 1 + Der f 1) levels were divided into tertiles with cut-offs 1.4 and 10.4 microg/g. Sensitization was assessed by measurement of allergen-specific immunoglobulin E against house dust mite. RESULTS: Prevalence ratios of mite sensitization for medium and high when compared with low mite allergen levels were 3.1 [1.7-5.7] and 1.4 [0.7-2.8] respectively. Highest mite sensitization rates at intermediate exposure levels were consistently observed across country (except for Sweden) and in both farm and nonfarm children. The shape of the dose-response curve was similar for above and below median mattress microbial agent levels, but the 'sensitization peak' appeared to be lower for above median levels. CONCLUSIONS: Our data suggest a bell-shaped dose-response relationship between mite allergen exposure and sensitization to mite allergens. In populations with high microbial agent levels and low sensitization rates, the curve is shifted down.     

Relationship among house-dust mites, Der 1, Fel d 1, and Can f 1 on clothing and automobile seats with respect to densities in houses.

BACKGROUND: Locations where there are no dust mites or pets present may contain allergens that pose a risk factor for sensitizing and inducing rhinitis and asthma. OBJECTIVE: The purpose of this study was to investigate the relationship among the prevalence of mites and mite, dog, and cat allergens in homes, on clothing, and on automobile seats. METHODS: Over a 2-year period (July 1998 to July 2000), dust mite and mite, dog, and cat allergen densities were determined in homes, associated automobiles, and on the clothing of the drivers. During this period 87 homes were sampled one to five times each. RESULTS: Low levels of live and dead mites were present in most dust samples obtained from automobile seats and in 16% from clothing. Seventy-two and 50% of the home samples had >2 microg and >10 microg Der l/g of dust, respectively, whereas 23% of automobiles seat samples had >2 microg Der l/g of dust with a mean of 1.3 microg/g. Mite and Der 1 densities were not different for homes with or without pets. However, homes with pets had significantly more Fel d 1 or Can f 1 allergen than homes without pets. Homes without cats and dogs had an average of 93 and 29 microg/g of Fel d 1 and Can f 1, respectively, which was well above threshold levels for sensitization and induction of allergic reactions. Although most clothing had detectable levels of pet allergen, the levels of these allergens were low. CONCLUSIONS: Der 1 densities in some automobiles were sufficiently high (>2 microg/g of dust) to be risk factors for sensitization and allergic reactions. However, most automobile seats had levels of dog and cat allergen that were well above the threshold levels considered to be risk factors for both sensitization and symptoms, regardless of the presence of a pet in the home. The presence of live and dead mites and mite, cat, and dog allergens in automobiles and on clothing suggests that both are vehicles in the dispersal of mites and mite and pet allergen.     

Mouse allergen exposure, wheeze and atopy in the first seven years of life

Background: Little is known about mouse allergen exposure in home environments and the development of wheezing, asthma and atopy in childhood. Objective: To examine the relation between mouse allergen exposure and wheezing, atopy, and asthma in the first 7 years of life. Methods: Prospective study of 498 children with parental history of allergy or asthma followed from birth to age 7 years, with longitudinal questionnaire ascertainment of reported mouse exposure and dust sample mouse urinary protein allergen levels measured at age 2–3 months. Results: Parental report of mouse exposure in the first year of life was associated with increased risk of transient wheeze and wheezing in early life. Current report of mouse exposure was also significantly associated with current wheeze throughout the first 7 years of life in the longitudinal analysis (P = 0.03 for overall relation of current mouse to current wheeze). However, early life mouse exposure did not predict asthma, eczema or allergic rhinitis at age 7 years. Exposure to detectable levels of mouse urinary protein in house dust samples collected at age 2–3 months was associated with a twofold increase in the odds of atopy (sensitization to >=1 allergen) at school age (95% confidence interval for odds ratio = 1.1–3.7; P = 0.03 in a multivariate analysis. Conclusions: Among children with parental history of asthma or allergies, current mouse exposure is associated with increased risk of wheeze during the first 7 years of life. Early mouse exposure was associated with early wheeze and atopy later in life.     

A longitudinal analysis of wheezing in young children: the independent effects of early life exposure to house dust endotoxin,allergens, and pets

BACKGROUND: It has been postulated that exposure to bacterial endotoxins and animals early in life might confer protection against the development of asthma and allergies. OBJECTIVE: We investigated the longitudinal effects of exposure to house dust endotoxin (HDE), allergen levels, and the presence of a dog in the home on wheezing in young children over a 4-year period. METHODS: Two hundred twenty-six children younger than 5 years were followed for 4 years. Endotoxin and allergen levels were measured from house dust collected at baseline. Longitudinal associations were investigated by using a proportional hazards technique that allowed for multiple outcomes per subject. RESULTS: Exposure to high concentrations of HDE of greater than the median level was associated with an increased risk for wheezing over the period of observation (multivariate relative risk, 1.52; 95 % CI, 1.07-2.14), but this risk rapidly decreased over time (P for trend =.005). Exposure to cockroach allergen was associated with increased risk for wheezing, whereas exposure to cat allergen and the presence of a dog in the home were both associated with decreased risk for wheezing. The risks associated with cockroach allergen, cat allergen, and dog did not change over the period of observation. CONCLUSION: The negative associations between exposures to dogs and cat allergen and wheeze appear to be independent of the effects of endotoxin and suggest that separate mechanisms might mediate the effects of HDE exposure and pet exposure on the developing immune system.     

Asthma, mite sensitization, and sleeping in bunks.

BACKGROUND: Mattresses and bedding are the main reservoirs of house dust mites. OBJECTIVE: Subjects sleeping in the bottom bunk may be exposed to house dust particles detached from bedding of the top bunk. Our aim was to ascertain whether this exposure could influence the development of mite sensitization and/or allergic symptoms in these individuals. METHODS: Symptoms of allergic respiratory disease were recorded and mite skin tests performed in 94 consecutive bunk-sleeping subjects (47 pairs of siblings) from an outpatient allergy clinic. Levels of Der p I, Der f I, and Der II were determined by enzyme-immunoassay in 16 randomly selected bedding dust samples (8 pairs of bunks). RESULTS: Mite sensitization rate and prevalence of allergic respiratory disease were similar for the top-bed and bottom-bed groups, whereas prevalence of asthma was significantly higher in the latter. Mite sensitization was significantly associated with family atopy background, whereas other factors such as house pets, indoor smoke exposure or types of mattress or bunks were not. Der p I levels higher than 2 microg/g dust were found in 12 of the 16 mattresses and the median of the 8-bed-bottom group was over 10 microg/g. CONCLUSIONS: Sleeping in bunks constitutes a greater risk of developing asthma for subjects sleeping in the bottom bed. Bunk sleeping should be discouraged in families with an atopic background and sensitized subjects should use the top bed.