Family history, dust mite exposure in early childhood, and risk for pediatric atopy and asthma

Background: Dust mite allergen exposure is considered a major determinant of sensitization to these allergens during childhood and a risk factor for pediatric asthma. Objective: By using a birth cohort in a setting with a substantial burden of dust mite allergen, we evaluated exposure and risk for outcomes related to allergy and asthma. Methods: We collected dust from the bedrooms of 428 children born from 1987 to 1989 and measured Der f 1 and Der p 1 (mug/g dust, combined). Follow-up at 6 to 7 years of age included clinical examination, skin prick testing, specific serum g measurement, and methacholine challenge. Results: No overall association was evident for any outcome except bronchial hyperresponsiveness (adjusted odds ratio [OR], 0.62; 95% CI, 0.38-1.00; P < .050; and OR, 0.53; CI, 0.27-1.04; P < .065 for dust mite allergen levels greater than or equal to2 mug/g and >10 mug/g, respectively). With a parental history of allergy and asthma, there was an association between a positive dust mite skin test (OR, 2.09; CI, 0.93-4.73; P < .076) and dust mite allergen level >10 mug/g. The inverse was true for children without a parental history. Dust mite exposure of >10 mug/g was associated with a decreased risk of current atopic asthma among children with a parental history (OR, 0.39; CI, 0.05-3.13; P < .376), but with increased risk if without a parental history (OR, 1.52; CI, 0.22-10.6; P < .673). Conclusion: Parental history is an important independent variable in the relationship between early dust mite exposure and atopic outcomes. Increased exposure during infancy is associated with a higher risk for sensitization in the presence of a positive parental history, but is protective among children of parents without a history of atopic disease.