Hives (urticaria), are red, itchy, raised areas of the skin that appear in various shapes and sizes that can appear suddenly and generally go away within 24-48 hours. They can appear round, in rings, or as patches on the skin, and can afflict any part of the body. An estimated 5% of people will suffer from hives at some point in their lives. Hives tend to change rapidly and move around the body, disappearing in one area and reappearing in another, sometimes with a few hours. Swelling deeper in the skin that may accompany hives is known as angioedema. Swelling from angioedema usually affects the eyes, lips, genitals, hands and feet.
- Ordinary hives:
Ordinary hives flare up suddenly and for no apparent reason. Welts, itchiness and swelling develop, and usually go away within a few hours, only to reappear elsewhere on the body. This process will repeat for days or weeks. If the problem persists for more than 6 weeks, the hives are generally categorized as "chronic." Chronic hives can last from months to years, and in about 80% of these cases, the cause cannot be determined, which can be frustrating.
- Physical hives:
Physical hives are those caused by direct stimulation of the skin, such as from cold, heat, sun exposure, pressure, sweating, or exercise. In this case, hives appear directly where the skin was stimulated, and nowhere else. This form of hives will diminish on its own, and should not reoccur.
Hives and angioedema form when, in response to histamine, blood plasma leaks out of small blood vessels in the skin. Histamine is a chemical released from cells along the skin’s blood vessels. The most common causes of hives are allergy, infection, or medication reactions, though we are often unable to identify the cause.
For patients with chronic hives, we evaluate by biopsy and a laboratory evaluation. Sometimes allergy testing is recommended. Treatment is aimed at relieving symptoms while the hives subside on their own. Antihistamines are the most effective agents, as they oppose the effects of histamine leaked by mast cells. The main side effect of antihistamines is drowsiness.
Oral steroids are sometimes used to temporarily treat severe cases of hives, though they have limited effectiveness because most cases of severe hives last longer than steroids can safely be taken. That is, steroids can have many adverse side effects, and long-term use can advance such risks.
Topical therapies for hives, including creams and lotions aim to numb nerve endings and reduce itching.
Other forms of treatment do exist for treating hives, although they are generally not needed. For example, ultraviolent radiation and agents that suppress the immune system can all be used in more persistent cases.