Urticaria, commonly referred to as hives, affects 15-20% of the general population at some time during their lifetime. It appears as raised, well-circumscribed areas of erythema and edema involving the dermis and epidermis that are very itchy. Pruritus (itching) and rash are the primary manifestations of urticaria. Urticaria results from the release of histamine, bradykinin, leukotriene C4, prostaglandin D2, and other vasoactive substances from mast cells and basophils in the dermis. These substances cause extravasation of fluid into the dermis, leading to the urticarial lesion. The intense pruritus of urticaria is a result of histamine released into the dermis. Acute urticaria is usually self-limited and commonly resolves within 24 hours but may last longer. Chronic urticaria, on the other hand, lasts more than 6 weeks. Neither acute nor chronic urticaria results in long-term consequences other than anxiety and depression. Current therapies to treat urticaria include antihistamine and corticosteroid but they are variably effective against chronic urticaira (Zuberbier T et al. Allergy 61(3):321-31, 2006
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