Allergic skin reaction in which slightly raised, flat-topped, very itchy swellings appear suddenly. The acute form, probably most often caused by food allergies, subsides in 6–24 hours, but the chronic form, believed to be due to emotional and mental stress, lasts much longer. Acute hives may also be triggered by drugs, especially penicillin, inhaled allergens or toxins, or diseases. Treatment involves identifying and avoiding the allergen; epinephrine and antihistamines may help the acute skin symptoms.
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