HOUSEHOLD AEROALERGENS IN THE INCEPTION OF INFANT ATOPY AND ASTHMA. THE AMICS STUDY.

Rationale: although widely assumed that incidence of childhood respiratory allergies 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. Objectives: to assess, in a prospective manner and in a general population, the role of early life exposures to Der p1 and Fel d1 upon the inception of sensitization and asthma. Methods: pregnant women and their children were recruited for the AMICS study. Overall, 1611 newborns were initially enrolled in three cohorts in the UK and Spain. Der p1 and Fel d1 allergens were measured in household dust samples at three months of age for 1474 (91.5%) participants and skin prick tests were performed at six years of age on 1182 (80.2%) of them. Wheeze and diagnosed asthma were reported in yearly questionnaires. Results: exposure to Der p1 early in life was not related with a positive specific prick test, nor with asthma or persistent wheeze at 6 years. Fel d1, however, showed an association with all these outcomes (third vs. first tertile OR: 4.43 for positive specific prick test and 2.6 for diagnosed asthma). Conclusions: dose-response relationships between allergen exposure and sensitization or asthma may be allergen specific and non-linear; a minimum threshold level would be needed to induce sensitization, but no dose-response relationship would exist above this level. In addition, the effect of a particular allergen appears to be very similar upon atopy and asthma inception.