Hives are well defined, itchy, raised patches of skin of any size and location. They usually fade within hours but can last several days. Many times swelling of the lips, palms or soles of the feet will accompany hives. Hives are very common, occurring in one quarter of the population during their lifetime.
Most episodes last less than a few weeks and are termed acute. Viral infections and allergy are the usual causes of acute hives. When allergy is present, a new food or medication is generally the problem. Examples include peanuts, milk, shrimp, eggs, penicillin or sulfa. Airborne allergens are rarely involved. The allergic trigger is obvious and with removal the hives disappear. We rarely need to order tests. The viral infections are self limited and the hives clear shortly after the infection. In adults reactions to medications are a common cause of acute hives. Medications known to cause hives or swelling include aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, hypertension medications known as ACE-inhibitors or narcotics such as codeine.
When hives continue for over four weeks they are referred to as chronic. Unlike the acute situation, chronic hives are rarely allergic. Avoidance of specific foods or medications is rarely helpful. An exception are NSAIDs.. These can worsen hives and we usually recommend avoidance. In fact, ninety percent of the cases have no demonstrable cause. Our approach is to make a thorough search for foods, medications, and illnesses in the initial interview. Selected laboratory tests may be necessary to exclude certain rheumatoid or inflammatory diseases. Allergy testing is usually not helpful unless indicated by the history. Sometimes we recommend an elimination diet if a frequently eaten food is suspected. Unfortunately, a thorough evaluation usually does not reveal the reason for the hives.
An understanding of the process leading to hives is helpful in coping with the problem. All individuals have histamine-containing mast cells in their skin. When the histamine is released from these cells, itching, swelling, and redness occur. The histamine can be released by infection, cold, heat, pressure, allergy and other factors. Most individuals with chronic hives have a change in their mast cells causing easy histamine release. The underlying change is usually unknown and the person is otherwise well.
Since a cause is usually not found, the primary treatment of chronic hives involves medications to suppress the action of histamine. Antihistamines in varying combinations are given daily to counteract the histamine being released. The dosage and types of medication will need adjusting until a beneficial response is seen. Many times the condition is only partially relieved. In difficult cases steroids are needed. Fortunately, the hives tend to diminish with the passage of time. Fifty percent of patients no longer require medication after six months. Seventy percent are hive free in one year. However, a small number continue with hives for many years and require continuing medication.