Outdoor aeroallergen impacts on asthma exacerbation among sensitized and non-sensitized Philadelphia children

Background Outdoor aeroallergens, such as pollens and molds, are known triggers of asthma exacerbation; however, few studies have examined children’s aeroallergen response based on sensitization. Objective To compare the relative impact of aeroallergen levels on asthma exacerbation between pediatric asthma patients who tested positive or negative for sensitization to particular allergens. Methods A case-crossover design study was conducted of associations between outdoor aeroallergen levels and asthma exacerbation events among children living in Philadelphia, Pennsylvania, who were treated within a large pediatric care network. Sensitization to common allergens was characterized in a subset of asthma exacerbation patients who had received skin prick testing (5.5%). Odds ratios (OR) and 95% confidence intervals (CI) were estimated among all asthma exacerbation cases, and in those sensitized or non-sensitized to aeroallergens. Results Children who were sensitized to a particular allergen had higher odds of asthma exacerbation with exposure to the allergen than did all asthma patients or non-sensitized patients – for early-season tree pollen, oak tree pollen, early-season weed pollen, and late-season molds. For example, the association between early-season tree pollen and asthma exacerbation among sensitized children (>90th percentile vs. ≤25th: OR=2.28, 95% CI: 1.23-4.22) was considerably stronger than that estimated among all cases (OR=1.34, 95% CI: 1.19-1.50), and was also substantially different from the lack of association seen among non-sensitized children (OR=0.89, 95% CI: 0.51-1.55, p-value for heterogeneity=0.03). Conclusion More prevalent allergy testing may be useful for prevention of asthma exacerbation by informing interventions targeted to sensitized children and tailored for particular aeroallergens.