Urticaria and angioedema: diagnostic and treatment considerations.

Urticaria and angioedema are common--and commonly frustrating--problems for physicians and patients alike. Patients often are in considerable distress with pruritus and uncomfortable lesions. They are frightened about their condition and frustrated when modern medicine cannot pinpoint the cause of the symptoms. Both urticaria and angioedema may be categorized as acute and chronic conditions. The dividing line between acute and chronic forms is relatively arbitrarily set at 6 weeks. A thorough history and physical examination may provide clues to the underlying cause, but in the majority of patients, the cause is rarely identified. One is more likely to discover the cause of acute than of chronic urticaria. A multitude of laboratory tests can be performed, but they often do not provide a diagnosis. It is not appropriate to do a large "screening" battery of laboratory tests. The dermal mast cells and their mediators play a central role in chronic urticaria. Chronic urticaria may have an autoimmune aspect. Recent evidence reveals that 50% of patients with chronic urticaria have a cutaneous autoimmune disorder mediated by autoantibodies to the high-affinity IgE receptor on mast cells. Biopsy may be necessary and may help with treatment.