Simply put, hives (urticaria) are an allergy of the skin. Hives will affect about 20 percent of the population at some time during their life. Hives generally start as itching that is quickly followed by the formation of raised, red, swollen welts of varying size. Hives can occur anywhere on the body and are classified as follows:
- Acute hives: hives that last for 6 weeks or less. Common causes of acute hives include: foods (peanuts, eggs, tree nuts, shellfish, and tree nuts are common food triggers), medications (antibiotics such as penicillin and sulfa drugs), insect bites or stings, certain infections. Acute hives are self-limiting and generally resolve on their own or with short term use of antihistamines.
- Chronic hives: hives that last for more than 6 weeks. In many cases the cause of chronic urticaria cannot be identified by a detailed history, skin testing, or laboratory studies (thyroid disease and other hormonal problems may trigger hives in some cases). Certain individuals may suffer from the so called physical urticaria syndromes where triggers may include: scratching of the skin, physical pressure on the skin, sudden changes in temperature of the skin, and sun exposure.
How do I determine what is causing my hives?
Very often the cause of hives is quite obvious - a new medication is taken, a highly allergenic food repeatedly results in hive formation (peanuts, shellfish), overheating of the body or sudden immersion in cold water results in a hive-like rash. Sometimes hives may be associated with areas of swelling, such as the tongue or throat. If this occurs, immediate evaluation by a physician is indicated. Keep a diary; easy to miss clues may rise to the surface on paper.
When should I seek the advice of an allergist?
If the hives are chronic, a detailed history and evaluation (skin testing and lab studies) by an allergist may help to determine the cause of your hives. Unfortunately, cause is determined in only about 20% of cases of chronic urticaria. The allergist can offer guidelines for eliminating foods from the diet, suggest the discontinuation of certain medications, or help to control certain environmental factors that may be triggering your hives. It is especially important to seek advice if you have associated symptoms of angioedema (swelling of the lips, tongue, or throat) that may compromise respiration.
Can my hives be treated?
In most situations, acute hives will resolve with short term use of antihistamines. More chronic forms of urticaria may require daily, or preventative, antihistamines to continually suppress the hives and in some cases it may be necessary to treat with oral steroid medications such as prednisone. An Epi-pen (self-injectable epinephrine) may be prescribed if you have had throat or tongue swelling that potentially interferes with normal breathing. If the allergist identifies one of the physical urticarias, treatment options may include avoidance of the trigger: wear loose fitting clothing to avoid pressure on the skin; avoid rubbing or scratching of the skin; avoid sudden exposure to cold temperatures such as ocean swimming; wear protective clothing when outside on sunny days.