Urticaria, or hives, is a common reason to see an allergist. It can be incredibly distressing to be covered with red welts, and the itching can disrupt sleep, school, and work. Hives appear quickly when special skin cells, called mast cells, are triggered to release chemicals that cause the rash.
Most cases of hives last only a short time and are triggered by allergic reactions, medications, or viral infections. Allergic reactions are possible to foods, bee stings, medications, or airborne substances. Hives can also be part of a severe, whole-body allergic reaction called anaphylaxis.
In some people, the skin mast cells can react and cause hives due to pressure, cold, heat, vibration, and exposure to the sun or water. Dermatographism (Latin for “skin writing”) refers to hives that pop up for only minutes after a scratch or irritation to the skin.
It is also possible to have hives lasting for weeks or months. This “chronic urticaria” is usually not due to a particular trigger, but instead it can result from abnormal immune reactions involving the mast cell. The severity of chronic hives can be affected by factors such as stress, medications, temperature, and illnesses.
It is important to identify the cause of hives if possible, and the first step is a careful interview and physical exam with an experienced medical professional. Episodes of hives due to foods, bee stings, medications, or allergens can often be sorted out with allergy testing. A simple cause is not often found for chronic urticaria, but laboratory testing can help sort out any source of inflammation or infection that could lead to long-lasting hives.
Once the cause is determined, it is important to avoid the cause of your hives if possible. Hives usually respond to medications that block histamine — the major chemical released by the mast cell. These “antihistamines” include the commonly used diphenhydramine (Benadryl®), but mild or ongoing cases of hives can also respond to longer-lasting and less sedating antihistamines, such as loratadine (Claritin®), cetirizine (Zyrtec®), or fexofenadine (Allegra®).
Under the care of an allergist, severe or persistent cases of urticaria can be treated with high dose antihistamines, the addition of other histamine blockers (ranitidine or similar drugs), or the temporary use of corticosteroids (such as prednisone). In severe cases of chronic urticaria, is it sometimes necessary to use other drugs that act on the immune system.
The physicians at Allergy Partners are experts in evaluating and treating the many possible causes of hives and allergic reactions. The evaluation begins with a careful interview and physical examination, followed by any necessary tests. These may include skin testing, which can be done during the initial visit if the patient is not taking antihistamines. For more information on Urticaria and skin testing, please visit our Patient Education page on our website or contact our office.