text: Urticaria, commonly known as hives, is a frequent complaint of patients in the ED. It consists of circumscribed areas of raised erythema and edema of the superficial dermis. Urticaria can be acute or chronic, and a variety of urticarial variants exist, such as hereditary angioedema and anaphylaxis. \n\nBy definition, the acute form of urticaria lasts less than 4-6 weeks, and the chronic form lasts more than 4-6 weeks. Although the treatment for urticaria is specific and straightforward, the list of causes is extensive. When a patient presents with acute urticaria within 24 hours of onset, a cause often can be determined. However, in many cases of both acute and chronic urticaria, the cause can be difficult or even impossible to determine. Thus, although the determination of the underlying etiology of urticaria represents a diagnostic challenge, the management of urticaria remains straightforward and generally successful.\nPruritus (itching) and rash are the primary manifestations of urticaria, and hyperpigmentation or hypopigmentation are rare. Acute urticaria is usually self-limited and commonly resolves within 24 hours but may last up to 4-6 weeks. Chronic urticaria lasts more than 4-6 weeks. Neither acute nor chronic urticaria results in long-term consequences (other than depression) or death