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 (μg/g dust, combined). Follow-up at 6 to 7 years of age included clinical examination, skin prick testing, specific serum IgE 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 ≥2 μg/g and >10 μg/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 μg/g. The inverse was true for children without a parental history. Dust mite exposure of >10 μg/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.