Epidemiological studies suggest a relationship between particulate air pollution and prevalence of allergic airway diseases such as allergic rhinitis, whose prevalance is getting increased in recent years. Diesel exhaust particles (DEP), which constitute the main fraction of particulate air pollution, have become a serious problem in Turkey, and worldwide as a result of increased use of diesel motor vehicles due to the low cost and high efficiency. DEP are composed of nanoscaled particles (< 0.1 μm) and larger particles. DEP act as carriers for the transport of allergens into the airways by binding allergenic proteins onto their surfaces. Studies investigating the mechanisms underlying effects of DEP on upper airways have demonstrated that DEP lead to increases in both the synthesis of total and specific IgE, and the response to the allergen-induced eosinophilic inflammation, and allergen presentation.