etiology 1. Genetic factors: multigene inheritance heritability 70-80% 2. Predisposing factors: air pollution 1)inhalants: dust mites, pollen ) infections 3) food 4) change of weather 5)mental factors 6) exercise运动 7)drugs 8)menstruation, pregnacyetiology • １．Genetic factors: multigene inheritance heritability 70-80% • ２．Predisposing factors: air pollution 1） inhalants：dust mites、pollen 2） infections 3） food 4） change of weather 5） mental factors 6） exercise运动 7） drugs 8） menstruation, pregnacy