[Urticaria].

ma are cutaneous manifestations of localized edema. They are common skin diseases that typically result from the same pathophysiologic processes. The primary difference between the disorders is that urticaria is associated with localized edema involving the upper dermis, whereas angioedema is associated with localized edema involving deeper layers of the skin, as well as subcutaneous and submucosal tissues. The diseases can affect persons of any age but most commonly affect young adults.1 Episodes of urticaria and/or angioedema persisting for fewer than 6 weeks are considered acute, whereas episodes persisting 6 weeks or more are considered chronic.1–5 Approximately 15% to 25% of Americans will experience at least a single episode of urticaria or angioedema during their lives.6 This article reviews the etiology, pathogenesis, clinical manifestations, diagnosis, and treatment of these skin disorders.