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 positive BHR (odds ratio (OR) 0.54, 95% CI 0.30-0.95). A severe respiratory infection early in life was protective of sensitization and wheeze combined (OR 0.29, 95%CI 0.12-0.74). Contact with dogs in the first year was a protective factor of rhinitis (OR 0.47, 95%CI 0.28-0.80), but contact with poultry and cats early in life increased the risk of rhinitis (OR 1.42, 95%CI 1.06-1.88; 1.82, 95%CI 1.06-3.14).

Conclusion: The pattern of associations between environmental exposure in early life and atopic conditions was inconsistent. The significant associations were evenly distributed as protective and risk factors of atopic conditions.