Exposure to multiple indoor allergens in US homes and its relationship to asthma

Background: The National Survey of Lead and Allergens in Housing was the first population-based study to measure indoor allergen levels in US homes. Objective: We characterized the overall burden to multiple allergens and examined whether increased allergen levels were associated with occupants' asthma status. Methods: This cross-sectional study surveyed a nationally representative sample of 831 housing units in 75 different locations throughout the United States. Information was collected by means of questionnaire and environmental assessment. Allergen concentrations in dust samples were assessed by using immunoassays. The following cutoff points were used to define increased allergen levels: 10 mu g/g for Der p 1, Der f 1, and Can f 1; 8 mu g/g for Fel d 1; 8 U/g for Bla g 1; 1.6 mu g/g for mouse urinary protein; and 7 mu g/g for Alternaria alternata antigens. Allergen burden was considered high when 4 or more allergens exceeded increased levels in any of the sampling locations. Results: Exposure to multiple allergens was common in US homes. Of the surveyed homes, 51.5% had at least 6 detectable allergens and 45.8% had at least 3 allergens exceeding increased levels. Race, income, housing type, absence of children, and presence of smokers, pets, cockroaches, rodents, and mold/moisture-related problems were independent predictors of high allergen burden. Among atopic subjects, high allergen burden increased the odds of having asthma symptoms (odds ratio, 1.81; 95% CI, 1.04-3.15). Conclusion: Increased allergen levels in the home are associated with asthma symptoms in allergic individuals.