Hives and Angioedema
Hives, also called urticaria, is a skin reaction characterized by pale, slightly elevated swellings (wheals) surrounded by an area of redness with clearly defined borders. Angioedema is swelling of larger areas of tissue under the skin, sometimes affecting the face and throat.
Hives and angioedema, which may occur together, can be severe. Common triggers are drugs, insect stings or bites, allergy injections (allergen immunotherapy), and certain foods--particularly eggs, shellfish, nuts, and fruits. Eating even a tiny amount of some foods can suddenly result in hives or angioedema. But with other foods (such as strawberries), these reactions occur only after a large amount is eaten. Also, hives sometimes follow viral infections such as hepatitis, infectious mononucleosis, and German measles.
Hives or angioedema can be chronic, recurring over weeks or months. In most cases, no specific cause is identified. The cause may be habitual, unintentional intake of a substance--for example, a food additive, such as a preservative or food dye. In some people, antibodies to thyroid hormone may be the cause. Use of certain drugs, such as aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) (see Section 6, Chapter 78), can also cause chronic hives or angioedema. In many cases, no specific cause can be identified. Chronic angioedema that occurs without hives may be hereditary angioedema.
Symptoms and Diagnosis
Hives usually begin with itching. Then wheals quickly develop. The wheals usually remain small (less than ½ inch across). Wheals that are larger (up to 4 inches across) may look like rings of redness with a pale center. Typically, crops of hives come and go. One spot may remain for several hours, then disappear, and later, another may appear elsewhere. After the hive disappears, the skin usually looks completely normal.
Angioedema may affect part or all of the hands, feet, eyelids, lips, or genitals. Sometimes the membranes lining the mouth, throat, and airways swell, making breathing difficult.
In children, when hives appear suddenly, disappear quickly, and do not recur, an examination by a doctor is usually unnecessary, because the cause is usually a viral infection. If the cause is a bee sting, seeing a doctor is important. A person can obtain advice about treatment if another bee sting occurs. When angioedema or hives recur without an obvious cause, an examination by a doctor is recommended.
Treatment
Usually, if hives appear suddenly, they subside without any treatment within days and sometimes within minutes. If the cause is not obvious, the person should stop taking all nonessential drugs until the hives subside.
For hives and mild angioedema, taking antihistamines partially relieves the itching and reduces the swelling. Corticosteroids are prescribed only for severe symptoms when all other treatments are ineffective, and they are given for as short a time as possible. When taken by mouth for more than 3 to 4 weeks, they cause many, sometimes serious side effects (see Section 5, Chapter 67).
In about half of the people with chronic hives, the hives disappear without treatment within 2 years. For some adults, the antidepressant doxepin, which is also a potent antihistamine, helps relieve chronic hives.
If severe angioedema results in difficulty swallowing or breathing or in collapse, prompt emergency treatment is necessary. Affected people should always carry a self-injecting syringe of epinephrine and antihistamine tablets to be used immediately if a reaction occurs. After a severe allergic reaction, such people should go to the hospital emergency department, where they can be checked and treated as needed.
 See the sidebar Hereditary Angioedema: Not an Allergy.
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