Hives (cont.)

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What causes hives and angioedema?

Hives are produced when histamine and other compounds are released from cells called mast cells, which are normally found in the skin. Histamine causes fluid to leak from the local blood vessels, leading to swelling in the skin.

Hives are very common. Although they can be annoying, they usually resolve on their own over a period of weeks and are rarely medically serious. Some hives are caused by allergies to such things as foods, medications, and insect stings, but in the majority of cases, no specific cause for them is ever found. Although patients may find it frustrating not to know what has caused their hives, maneuvers like changing diet, soap, detergent, and makeup are rarely helpful in preventing hives unless there is an excellent temporal relationship.

Having hives may cause stress, but stress by itself does not cause hives.

When to visit the doctor

In rare cases (some hereditary, others caused by bee stings or drug allergy), urticaria and angioedema are accompanied by a striking decrease in blood pressure (shock) and difficulty breathing. This is called anaphylaxis and may rapidly become a medical emergency. In this case, a visit to the emergency room or your doctor is necessary. Ordinary hives may be widespread and disturbing to look at, but the vast majority of cases of hives do not lead to life-threatening complications.

Medically Reviewed by a Doctor on 7/2/2013

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