A skin condition, also known as nettle rash or hives, that is characterized by the development of itchy weals, usually on the limbs and trunk. Large weals may merge to form irregular, raised patches. Urticaria is generally harmless and usually lasts only a few hours. Sometimes a persistent or recurrent form develops. Dermographism is a less common form of urticaria in which weals form after the skin is stroked. Urticaria sometimes occurs with angioedema. The cause of urticaria is often unknown. The most common known cause is an allergic reaction (see allergy), often to a particular food, food additive, or drug. Urticaria may also be caused by exposure to heat, cold, or sunlight. Less commonly, it may be associated with another disorder, such as vasculitis, systemic lupus erythematosus, or cancer. Itching can be relieved by applying calamine lotion or by taking antihistamine drugs. More severe cases may require corticosteroid drugs. Identifying and avoiding known trigger factors can help prevent future reactions. A tendency to urticaria often disappears in time without treatment.


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