Most people recognize hives - those sudden instances of swelling of the skin that usually itch, burn, or sting. Less familiar, however, is the condition's close cousin, angioedema, a similar kind of swelling of the deeper tissues beneath the skin.
Hives and angioedema are related because they are similar reactions to the same basic cause, a release in the skin of chemicals including called histamine. In most cases, histamine is and these other chemicals are a byproduct of the body’s specialized mast cells as they go about their job of destroying allergens, which are any substances that cause allergic reactions. Fighting allergens is not the only way that histamine is produced, however. Irritation caused by sunlight, some medications, and unknown sources can make mast cells release histamine, too.
Whatever the reason for its release, histamine produces hives and angioedema by dilating the small blood vessels in the skin and causing fluid to leak from them. This in turn generates swelling. It also can stimulate gastric acid secretion and cause certain smooth muscles to contract.
Hives—or more technically, urticaria—are pale red welts that can appear anywhere on the body in splotches as small as a pencil eraser and as large as a dinner plate. These splotches sometimes join together to form larger areas known as plaques. Whether large or small, hives and plaques often fade within a few hours, but can last up to a day or longer.
In general, angioedema lasts longer than urticaria, but the swelling usually goes away within 24 hours. Symptoms include deep swelling around the eyes and lips, and sometimes swelling of the genitals, hands, and feet. Occasionally, severe and prolonged swelling of the tissue can be disfiguring. In rare instances, angioedema of the throat, tongue, or lungs can block the airways, making breathing difficult and potentially endangering the life of the victim.
Doctors usually classify hives and angioedema according to the following categories:
The best treatment for hives and angioedema is for your doctor to identify the trigger and then for you to avoid it. Identifying triggers, however, is not an easy task. Your doctor will need to ask you many questions and may perform some tests.
Because there are no specific tests for hives or angioedema, the kinds of tests ordered will depend upon your medical history and a thorough examination by one or more specialists. Skin tests may be performed to determine the substance to which you are allergic. Blood tests are frequently done to rule out a systemic illness as the cause of your body's release of histamine.
If your condition is persistent, your doctor will probably prescribe an antihistamine to provide you with relief from the symptoms. These medications work best when taken on a regular schedule to prevent the swelling. For severe outbreaks, an injection of epinephrine (adrenaline) or a cortisone-based medication may be needed. Your doctor may prescribe oral corticosteroids if antihistamines do not work well. In many cases, antihistamine medications need to be advanced, as tolerated, to higher doses than when antihistamines are used for other conditions (e.g., allergic rhinitis or hay fever). A number of medications can be prescribed for patients with “antihistamine resistant” urticaria that can achieve control of this condition.
While you're waiting for the hives and swelling to disappear, doing the following might help to relieve the symptoms:
Most of the time, hives will go away by themselves and need no treatment. You should contact your doctor if:
Go to an emergency room immediately if any of the following symptoms accompany the development of your hives or angioedema:
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition. This document was last reviewed on: 01/15/2014