Patient Education

ALL ABOUT HIVES

Copyright 2000, Regional Allergy & Asthma Consultants, PA

WHAT ARE HIVES?

Hives are red, raised, itchy bumps on the skin that typically look most like mosquito bites. They may occur anywhere on the body, and can range in size from a few millimeters to a few inches in diameter. Sometimes they are associated with swelling under the skin, called angioedema, which burns more than itches, and most often involves the eyelids, lips, tongue, hands and feet.

Hives are caused by the release of one of the body's own chemicals, histamine, into the skin. Histamine causes blood vessels to dilate, leaking fluid. This leads to swelling and redness, along with intense itching.

Each individual hive usually lasts less than a day, and sometimes less than an hour or two. Hives tend to come and go, reappearing at other sites of the body. They may cause discomfort lasting anywhere from just a few hours up to several years, as in some chronic cases.

WHO GETS HIVES?

People of virtually any age may get hives, including infants and the elderly. Most people experience hives at some time or another in their lives. One does not have to be allergic to anything to develop hives. In fact, the majority of cases of hives, especially when chronic, are not caused by an allergy.

WHAT CAUSES HIVES?

Hives may be caused by virtually anything that triggers release of the body's own histamine into the skin. The following are among the most common causes:

1. Allergic reactions. Allergic reactions to foods, medicines, bee stings, and environmental factors may trigger hives. These are almost always associated with acute, or short-lived episodes of hives, and the causative factor is often obvious.

The foods most commonly associated with allergic reactions include milk, egg, wheat, soy and peanut in infants and young children; and peanuts, tree nuts, and seafood in older children and adults. Virtually any food can cause an allergy, but it is rare for more than 1-2 foods to truly cause a problem in any given person. Food allergies are almost never the cause of chronic hives.

Medication allergies are common, especially to antibiotics in the penicillin and sulfa families. Other drugs, such as narcotic pain medicines (e.g. codeine) and antiinflammatory pain medicines (e.g. aspirin and ibuprofen) may trigger hives, but technically not on an allergic basis. They rather act directly or indirectly on the skin to cause release of histamine.

Allergic reactions to insect stings may cause hives in up to 1-2% of the population. The most common are yellow jackets, hornets, wasps, honeybees, and fire ants.

Patients with inhalant allergies, especially to pollens and animal danders, may develop hives during particularly severe allergy flare-ups. In these cases the hives accompany intense nasal and/or eye allergy symptoms, as well.

2. Infections. Viral infections, especially in young children, commonly trigger episodes of hives lasting anywhere from a few days to a few weeks. This is part of the body's immune response to fight off the infection. Smoldering bacterial infections, such as dental abscesses or sinusitis, may also cause hives in some cases.

3. Physical factors. Occasionally, hives develop due to any number of direct physical stimuli to the skin, such as heat, cold, vibration, or even sunlight. The hives usually occur only at the exposed site. In the case of cold-induced hives, reactions may be quite severe- involving the whole body if the person becomes cold very quickly (i.e. jumping into a cold lake).

4. Emotional stress. Like many other medical problems, hives can be worsened by emotional stress. It is generally felt however, that stress is not the underlying cause of hives but lowers ones threshold for breaking out.

5. Other underlying medical conditions. Very occasionally, hives can signal the presence of underlying disease, ranging from parasites to liver, kidney, thyroid, blood, and other disorders. Therefore, patients with unexplained chronic hives should have a thorough history and physical from their primary care physician to rule-out the possibility of any underlying diseases.

6. Idiopathic. This is the medical term for essentially no known cause," and unfortunately accounts for the vast majority of cases of chronic hives. Sophisticated research, however, has shown that many patients with chronic hives may have an autoimmune response; that is, they appear to make an antibody which triggers the release of histamine in the skin. This is similar to what occurs in other autoimmune problems (e.g. thyroid disease, lupus, rheumatoid arthritis). In fact, patients with other autoimmune diseases seem to be more likely to develop hives. No one really knows what causes autoimmune problems; there may be an inherited tendency, and are more common in women.

HOW ARE HIVES EVALUATED?

We generally start by taking a careful history, which in most cases will suggest either a probable cause or point toward an idiopathic condition. We may perform allergy testing to rule out an allergic cause, and in some cases, blood work as well. Depending on the nature of the hives, we may need to have a dermatologist see you for evaluation as well.

If no allergy or other specific cause is identified, and if the hives are chronic or recurrent, we may recommend you see your primary care physician to rule out the rare possibility of any underlying diseases predisposing you to hives.

HOW ARE HIVES TREATED?

Unfortunately there is no "cure" for hives, except in cases where there is an identifiable cause that can be eliminated.

Most often, we use antihistamines to control the itch and reduce the severity of hives. Although many people with hives have already used antihistamines, most have not used them properly. In contrast to treating hives after they have developed, we will often recommend they be used daily to prevent hives from occurring in the first place. Typically, we will start with a non-sedating antihistamine but may add additional antihistamines as needed to further help the itch and facilitate sleep and comfort.

In severe cases, oral steroid medicines may be needed to achieve control of hives. Because of the potential side effects of oral steroids, we aim for the lowest dose over the shortest time possible.

Several other types of medications have been tried in cases of chronic hives, with variable results. Unfortunately, topical creams, ointments, or lotions are not helpful in the majority of patients, since hives develop in the inner layers of the skin rather than the external surface of the skin.

WHAT IS THE PROGNOSIS OF CHRONIC HIVES?

Persistent hives tend to last anywhere from several weeks to several years. Often they disappear just as mysteriously and unexpectedly as they appeared. Rarely do they last a lifetime. There is no way to predict when a case of chronic hives will disappear.

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Last updated 8/11/00

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