June 23, 2017

Hives (Urticaria & Angioedema)

What causes hives and angioedema? Are hives contagious? Does stress cause hives?

Hives appear 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 and are not considered contagious. Although annoying, hives usually resolve on their own over a period of weeks and are rarely medically serious. Some hives may be caused by allergies to such things as foods, infections by different organisms, medications, food coloring, preservatives and insect stings or bites, and chemicals; but in the majority of cases, no specific cause is ever found. Although people 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. Since hives most often are produced by an immune mechanism, the condition is not contagious. If an infectious disease were the cause of hives in a particular person then it is possible, but not likely, that an infected contact could develop hives.

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

What are the different kinds of hives?

Hives fall into two categories on the basis of the time they have been present: acute urticaria (ordinary hives, which resolve after six to eight weeks) and chronic urticaria (that continues longer than six to eight weeks). Since hives are so common and acute urticaria, by definition, resolves spontaneously, physicians do not generally expend much time or expense to evaluate the cause of hives of less than eight weeks' duration.

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Reviewed on 11/14/2016