Four major issues concerning the interaction of outdoor pollutant and allergens include the following: (1) epidemiological studies of pollution and aero allergens on the genesis of asthma; (2) epidemiological studies of pollution and aero allergens on the exacerbation of asthma;(3) experimental studies on the adjuvant effect of pollutant particulates (DEPs) on specific TH2 responses; and (4) the role of pollution and global warming on natural allergen production.