Hives, also known as urticaria, are a skin rash that can be caused by an allergic reaction to something you ate or touched, or an underlying health issue. Hives are raised, red, and sometimes itchy bumps on the skin that can range in size from a few millimeters to the size of a dinner plate. They can appear on one part of the body or spread over large areas. Hives can be acute, lasting for a short time, or chronic, lasting for more than six weeks and recurring often over months or years.

Histamine and other chemicals are released from under the skins surface when hives occur, causing the tissues to swell. Histamine can be released for many reasons, including eating certain foods, an insect bite or sting, cold or heat exposure, emotional stress, an infection, taking certain medications, or a problem with the immune system. If hives last more than a month or recur over time, it is recommended to see an allergist who can take a history and perform a thorough physical exam to try and determine the cause of the symptoms.

Treatments for hives range from cool compresses to relieve itching to prescription antihistamines and other drugs, such as anti-inflammatory medications and medications that may modify the immune system. Antihistamines are a frequently recommended treatment for hives, as they work by blocking the effect of histamine, a chemical in the skin that can cause allergy symptoms, including welts. If hives are accompanied by a severe allergic reaction, seek emergency medical care.