Abstract Allergic rhinitis affects more than 20% of the population of Westernized countries and has a significant impact on quality of life and school/work performance. Important environmental factors include tree and grass pollens (seasonal allergic rhinitis); house dust mite and domestic pets, most often cats (perennial allergic rhinitis); and a variety of occupational exposures (occupational rhinitis). Pathogenesis involves activation of type 2 (Th2) lymphocytes resulting in IgE antibody production and tissue eosinophilia. Immediate symptoms (itching, sneezing, and watery nasal discharge) result from allergen cross-linking adjacent IgE molecules on the surface of mast cells in the nasal mucosa, resulting in the release of histamine and tryptase, and generation of bradykinin. Diagnosis is usually straightforward and based on the history, examination, and (when indicated) the results of skin prick tests and/or serum allergen-specific IgE levels.