Early-life domestic aeroallergen exposure and IgE sensitization at age 4 years.

BACKGROUND Although it is widely assumed that childhood sensitization to common aeroallergens is directly related to allergen exposure in early life, few longitudinal studies have investigated this issue, and available data are scarce and mainly limited to high-risk groups. OBJECTIVE We sought to assess the role of early exposure to 2 major household aeroallergens (Der p 1 and Fel d 1) in sensitization at the age of 4 years. METHODS Pregnant women and their children were recruited for the Asthma Multicenter Infant Cohort Study. Three cohorts (Ashford in the United Kingdom and Menorca and Barcelona in Spain) followed the same research protocol. A total of 1611 newborn children were initially included in the cohort, from whose homes we collected dust samples at 3 months of age for 1474; Der p 1 and Fel d 1 levels were measured. Of these children, we obtained blood for specific IgE determination in 1019. RESULTS The risk of Fel d 1 sensitization increased with exposure in a nonlinear manner. No association was found between specific IgE to Der p 1 and aeroallergen levels of exposure at early life in 2 centers, but a positive association was observed in the third. CONCLUSIONS The dose-response relationships between allergen exposure and sensitization differ between allergens and might vary between different locales. The hypothesis that sensitization to house dust mite is directly related to levels of allergen exposure might not apply to the general population or to different ranges of exposure. CLINICAL IMPLICATIONS Aeroallergen avoidance might not have any important effect on the incidence of sensitization.