The prevalence and incidence of allergic disease have increased during the last decade in most industrialized and developing countries in the world. Recent human and animal laboratory-based studies have proposed that persistent exposure to traffic-related pollution, especially particulate matter <10microgram in diameter (PM(10)) from motor vehicles can enhance allergic inflammation and induce the development of allergic immune responses. In particular, the association between traffic-related pollution and asthma has been observed in many epidemiologic studies. Traffic-related pollution has been estimated by developing new indicators, such as the distance to main roads, road lengths within certain buffer, traffic counts, NO2 and PM(10) concentration calculated by land use regression (LUR) model. Even though there still remain uncertainty and the data gap between traffic-related pollution and allergic rhinitis or atopic dermatitis, some studies have reported significant associations between them. Changes by traffic-related pollutants are regarded as biomolecular indicators for the susceptible population of asthma and other allergic diseases. Long-term studies, including environmental exposure in early life and gene-environment interactions, are needed to prevent and decrease the development of asthma and other allergic diseases.