Urticaria (hives) is a common disorder that affects 15 to 20 percent of the population at some time. Lesions are clinically characterized by a transient, pruritic, patchy eruption that consists of lightly erythematous papules or wheals. When attacks are protracted, urticaria is an annoying condition for the patient and a challenge for the physician. Foods, drugs and many other agents may cause urticaria by inducing mediator release from mast cells in the skin. Identification of the precipitating agent is crucial for effective treatment of urticaria. Newer antihistamines that are nonsedating offer promise for control of symptoms without the problem of frequent side effects.