Mite, cat, and cockroach exposure, allergen sensitisation, and asthma in children: a case-control study of three schools

Background-The amount of allergen necessary to sensitise generically "at ri sk" children is unclear. The relation between allergen exposure and asthma is also uncertain. Methods-To ensure a wide range of allergen exposures the data from case-con trol studies of asthma in children aged 12-14 years attending three schools in Los Alamos, New Mexico and Central Virginia were combined. Skin prick t ests to indoor and outdoor allergens and bronchial hyperreactivity to hista mine were assessee in children with and without symptoms of asthma. The con centration of mite, cat, and cockroach allergens in dust from the children' s homes was used as a marker of exposure. Results-Three hundred and thirty two children (157 with asthmatic symptoms and 175 controls) were investigated. One hundred and eighty three were clas sified as atopic on the basis of allergen skin prick tests and 68 as asthma tic (symptoms plus bronchial responsiveness). The prevalence and degree of sensitisation to mite and cockroach, but not cat, was strongly associated i n atopic children with increasing domestic concentrations of these allergen s. Asthma was strongly associated with sensitisation to indoor allergens (p <10(-6)) and weakly to outdoor allergens (p = 0.026). There was an associat ion between current asthma and the concentration of mite allergen amongst a topic children (p = 0.008) but not amongst those who were specifically mite sensitised (p = 0.16). Conclusions-The domestic reservoir concentration of mite and cockroach, but not cat, allergen was closely related to the prevalence of sensitisation i n atopic children. However, the prevalence of current asthma had a limited relationship to these allergen measurements, suggesting that other factors play a major part in determining which allergic individuals develop asthma.