Urticaria--a challenge in diagnosis and treatment.

Urticaria can be caused by a multitude of factors, both internal (eg, ingested drugs or foods) and external (eg, skin contact, heat, cold). Skin testing, ice-cube testing, skin biopsy, and food-challenge testing are some of the methods that can help link cause and effect. Acute urticaria may require the administration of epinephrine and diphenhydramine or a lowering of the antigen dose in an allergy shot. Chronic urticaria is plainly visible in clinical presentation but is more elusive in diagnosis and treatment. It constantly challenges the physician's investigative acumen.