EFFECTIVE ALLERGEN AVOIDANCE AT HIGH-ALTITUDE REDUCES ALLERGEN-INDUCED BRONCHIAL HYPERRESPONSIVENESS

We studied the effects of reduced allergen exposure on bronchial hyper eactivity (BHR) in two groups of asthmatic children allergic to house dust mites (HDM) living at high altitude for 9 continuous mo. In the f irst group the serum levels of total and HDM-specific IgE showed signi ficant decreases after 3 mo (p < 0.001 and p < 0.02, respectively) and after 9 mo (p < 0.001). Three months after returning home the total I gE levels had increased significantly (p < 0.001). The mean percentage fail in peak expiratory flow after exercise testing improved after 3 and 9 mo (p < 0.05), but it had deteriorated after 3 mo at home (p < 0 .01). The methacholine PD20-FEV(1) increased after 3 mo (p = 0.001) an d further after 9 mo (p < 0.001), with a decrease after the 3-mo perio d at sea level (p = 0.01). In the second cohort there was a significan t increase in HDM PD20-FEV(1) after 6 and 9 mo (p < 0.001), with a sli ght decrease of magnitude of the allergen-induced late reaction. Hista mine PD20-FEV(1) significantly increased after 6 and 9 mo at high alti tude, particularly in the challenges performed after the HDM bronchial provocation (p < 0.01). Our data demonstrate that allergen avoidance in asthmatic children not only decreases nonspecific BHR but also decr eases allergen sensitivity, late allergen-induced bronchial reactions, and enhancement of BHR by allergen challenge.