The Itchies Urticaria Hives - Managing Your Allergies: Allergies

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The itchies: Urticaria (hives)

Urticaria, commonly known as hives, appears as a raised, itchy, spotty rash on the skin. The rash is red, although each spot, or hive, can be pale in the center. The hives are typically 1–2 centimeters (3/8–3/4 inch) in diameter, but they can be as small as 1–2 millimeters or as large as the palm of your hand. They can appear anywhere on the body. Hives can occur as an acute reaction to a drug, food, or insect sting; in these cases, they are a classic allergic reaction due to an allergen binding to IgE on the mast cells in the skin. Some people develop hives that come and go, sometimes on a daily basis, for weeks to years. In this case, the hives are rarely due to a true allergy, and the chance of finding a cause is less than 10%. Stress sometimes worsens hives.

If you have chronic hives, it’s important to identify any possible triggers. Your doctor will ask you about physical triggers — for example, heat, cold, sunlight, or sites of pressure from clothing. Many people think that their chronic hives are caused by foods, environmental allergens, or detergents in their clothing, but this is rarely the case. Hives have been described in association with many different conditions, although a cause is seldom found. Nevertheless, your doctor will take a thorough history and will want to examine you for any signs of underlying disease. Since hives can be associated with thyroid disease, your doctor will likely check your thyroid function and test your blood for antibodies against the thyroid gland.

The cause of chronic urticaria remains a mystery. However, reports indicate that as many as 50% of people with hives have detectable antibodies directed to IgE or to its receptors on the surface of mast cells. This intriguing observation suggests that these antibodies may be the cause of the hives by triggering the mast cell to react as though it is exposed to an allergen. However, this has not yet resulted in new treatments for hives.

Treating urticaria

The most effective treatment for hives is an antihistamine. A second-generation, non-sedating antihistamine may suffice, although often it has to be combined with a different kind of antihistamine usually used to treat heartburn — one of the H2 blockers, such as ranitidine (Zantac). If that combination does not work, your doctor may suggest one of the older, first-generation antihistamines, such as hydroxyzine (Atarax) or chlorpheniramine (Chlor-Trimeton), which are often more effective in treating hives. Although they can cause drowsiness, this effect tends to wear off over time even though the medications continue to provide relief from the hives. Antileukotriene medications may also be helpful.

If these simpler measures do not work, your doctor may prescribe a drug like doxepin (Sinequan) to ease the hives and help you sleep at night, and may also recommend one of a variety of immunosuppressive drugs, such as the steroid drug prednisone. Some patients need to take prednisone on a regular basis, preferably on alternate days, to control their hives until they subside (which is difficult to predict). If you find yourself in this situation, take precautions to prevent bone loss and work with your doctor to monitor and prevent complications of steroid use.

Last updated:	August 21, 2006
Reviewed By:	Faculty of Harvard Medical School