Urticaria can be acute or chronic, and may be allergic (mediated by immunoglobulin E) or nonallergic (mediated by pharmacologic effects of drugs such as aspirin or an acute-phase response). There are variants of urticaria that are caused by physical factors such as exposure of the skin to pressure, vibration, cold, or even water (aquagenic urticaria). Urticarial lesions are produced in the skin by the degranulation of mast cells. Urticaria can be a presenting sign of urticarial vasculitis. Chronic urticaria is the common presentation of this condition, and in most instances it is not possible to identify an etiology (idiopathic urticaria). There are a multitude of causes of urticaria, including food or medication allergies, infections, as well as in association with autoimmune diseases such as thyroid disease. Histamine-releasing autoantibodies are thought to be one of the possible causes of urticaria. Treatment is based on identifying a trigger factor. If this is not possible, short courses of glucocorticosteroids are warranted. Antihistamines are a cornerstone of treatment. For more severe cases, immune modulating drugs such as cyclosporine may be necessary to control signs and symptoms of this process. Biologic agents such as rituximab and omalizumab are promising.
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