Allergic diseases and asthma has long been hypothesized as the results of the dysregulation of type 2 immune responses to environmental allergens. Recent progresses in characterizing the proinflammatory IL-17 cytokine family have added additional layer of complexity on the regulation of allergic inflammation. The delineation of IL-17-producing CD4+ T cell subset (Th17) has led to the revision of Th1/Th2 paradigm and impacts our perspectives on the basis of chronic tissue inflammation. In addition, the distinctive expression patterns and biological activities of individual IL-17 cytokine member may play different roles in the regulation of the pathogenesis of allergic diseases. Understanding the cellular source and targeting cells of IL-17 cytokine family member will provide the basis to elucidate the cellular mechanism underlying allergic inflammation and improve our therapeutic approaches for allergy.