Hives are raised, red, and extremely itchy “welts” (called wheals) on the skin surface that can last minutes to hours. In medical writing, hives are often referred to as urticaria.
Hives are a common problem that can disrupt sleep, school, and work. They appear quickly when special skin cells called mast cells are triggered to release chemicals that cause the redness, itching, and swelling. Hives can be part of a severe, whole-body allergic reaction called anaphylaxis.
Most cases of short-lasting hives are triggered by allergic reactions, medications, or viral infections. Allergic responses to foods, bee stings, medications, or airborne substances can all cause hives.
Physical factors such as pressure, cold, heat, or vibration can also provoke urticaria in certain people. Dermatographism (Latin for “skin writing”) refers to hives that pop up for only minutes after a scratch or irritation to the skin.
It is 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 other factors such as stress, medications, temperature, and illnesses.
Individual hives are itchy, raised, and red. The wheals are often paler in the middle. Severe itching is almost always present. The size of hives can range from small bumps to large wheals that spread over an entire body region. Patients with hives often have areas of deeper skin swelling called angioedema. Hives should not leave behind bruising, blistering, or other skin changes unless there’s been severe scratching.
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 these issues.
Severe allergic reactions (anaphylaxis) often include hives in addition to other symptoms. In this event it is important to contact emergency services and use an epinephrine auto-injector if available. For hives alone, it is important to identify and avoid the cause 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 longer-lasting and less sedating antihistamines such as loratadine (Claritin®), cetirizine (Zyrtec®), or fexofenadine (Allegra®). Severe or persistent cases of urticaria can be treated with the addition of medications such as high dose antihistamines, ranitidine (or similar drugs), and temporary use of corticosteroids (such as prednisone). In severe cases of chronic urticaria, it is sometimes necessary to use other drugs that act on the immune system.
How We Can Help
Allergy Associates caregivers are experts in evaluating the many possible causes of hives and allergic reactions. The allergists with Allergy Associates are also trained to provide treatment options that can include avoidance and medications. The evaluation is centered on a careful interview and physical examination, followed by any necessary tests. The tests may include skin testing, which can be done during the initial visit if the patient is not taking antihistamines.
Check out these links to other resources:
American College of Allergy, Asthma, and Immunology