November 25, 2015

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Hives (Urticaria & Angioedema)

What are the signs and symptoms of ordinary hives?

Ordinary hives flare up suddenly and usually for no specific reason. Welts appear, often in several places. They flare, itch, swell, and go away in a matter of minutes to hours, only to appear elsewhere. This sequence may go on from days to weeks. Most episodes of hives last less than six weeks. Although that cutoff point is arbitrary, cases of hives that last more than six weeks are often called "chronic."

What are the causes of ordinary hives?

As noted above, many cases of ordinary hives are "idiopathic," meaning no cause is known. Others may be triggered by viral infections. A few may be caused by medications, usually when they have been taken for the first time a few weeks before. (It is uncommon for drugs taken continuously for long periods to cause hives or other reactions.) When a medication is implicated as a cause of hives, the drug must be stopped, since testing is rarely available to confirm the cause. In most cases, drug-induced hives will go away in a few days. If a drug is stopped and the hives do not go away, this is a strong indication that the medication was not in fact the cause of the hives.

Some medications, like morphine, codeine, aspirin, and other nonsteroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen [Advil]), cause the body to release histamine and produce urticaria through nonallergic mechanisms.

Despite the reputation of hives being an "allergic" condition, there is characteristically no obvious connection to a provoking substance. In this situation, allergy testing is not usually helpful. Continue Reading

Reviewed on 10/13/2015