Childhood Environment and Atopic Conditions, with Emphasis on Asthma in a Chilean Agricultural Area

Background. An explanation of the etiology of atopic conditions based on the hygiene hypothesis remains controversial. Objective. To analyze exposure variables in childhood to assess their impact on hay fever, asthma, and sensitization. Methods . Data were collected on 1,232 young Chilean adults born between 1974 and 1978. Information was available on consultations for infections early in life, number of siblings, sharing a bedroom, nursery school attendance, and contact with animals in the first 5 years of life. Information on asthma symptoms and rhinitis were obtained from a standardized questionnaire. Sensitization to eight allergens and bronchial hyper responsiveness (BHR) to methacholine were assessed. The study design was non-concurrent longitudinal for infectious episodes and nutritional status in the first year and cross-sectional for the other outcomes. Results. Number of siblings was associated with sensitization only (p = 0.0048). Nursery school attendance was negatively associated with positiv...