Urticaria, also known as hives, are localized, pale, itchy, pink wheals (swellings) that can burn or sting. They may occur singularly or in groups on any part of the skin. They are part of an allergic reaction and are very common. Approximately 10-20 percent of the population will have at least one episode in their lifetime. Most episodes of hives disappear quickly in a few days to a few weeks. Occasionally, a person will have them for many months or years. New hives may develop as old ones fade. Hives can vary in size from as small as a pencil eraser to as large as a dinner plate, and may join to form even larger swellings.
Hives are produced by blood plasma leaking through tiny gaps between the cell lining small blood vessels in the skin. Histamine is a chemical released from cells in the skin called "mast cells" which lie along blood vessels. Allergic reactions, chemicals in foods, or medications may cause hives; sometimes it is impossible to find out the cause. When hives form around the eyes, lips, or genitals, the tissue may swell excessively. Although frightening, the swelling usually goes away in less than 24 hours. Severe cases of hives may cause difficulty in breathing or swallowing and emergency room care is required.
Acute urticaria lasts less than six weeks. An underlying cause can be frequently identified and eliminated. The most common causes for acute urticaria are foods, drugs, or infections. Insect bites, internal diseases, pressure, cold, or sunlight also may be responsible.
The most common foods that cause urticaria are: nuts, chocolate, shellfish, tomatoes, eggs, berries, and milk. Fresh foods cause hives more often than cooked foods. Food additives and preservatives may also cause hives.
Hives may appear within minutes to several hours after eating, depending upon the site within the digestive tract where the food is absorbed.
Almost any medication -- prescription or over-the-counter -- can cause hives. Antibiotics, pain medications, sedatives, tranquilizers, diuretics (water pills), diet supplements, antacids, arthritis medication, vitamins, herbal supplements, eye and eardrops, laxatives, vaginal douches, or any other non-prescription item can be a potential cause of urticaria. It is important to inform the dermatologist of ALL prescription and over-the-counter medications being used to help find the cause of the hives.
Many infections can cause urticaria. Viral upper-respiratory tract infections (colds) are a comon cause in children. Other viruses, including hepatitis and a number of bacterial and fungal infections, may cause urticaria.
Chronic urticaria lasts more than six weeks. The cause of chronic urticaria is more difficult to identify and is found only in a small percentage of patients. The dermatologist reviews a patient's medical history, asks extensive questions, and conducts a thorough physical examination. Testing, such as blood work or a biopsy, may be necessary.
Physical urticaria may be caused by sunlight, heat, cold, water, pressure, vibration, or exercise. Solar urticaria forms within minutes of sun exposure and typically fades within one to two hours. Cold urticaria appears when the skin is warmed after exposure to cold. Urticaria, which forms in response to the cold or the water when swimming, for example, can produce wheezing, flushing, generalized hives, and fainting.
Dermatographic Urticaria (Dermatographism)
Dermatographic urticaria forms after firmly stroking or scratching the skin, and can often occur with other forms of urticaria. It affects about five percent of the population. Most people with this condition are otherwise healthy. Dermatographism may last for months or even years.
The best treatment for urticaria is to find and eliminate the cause whenever possible. Antihistamines are prescribed to provide relief and work best if taken on a regular schedule to prevent hives from forming. There are many antihistamines available. No one antihistamine works for everyone. The dermatologist may use combinations to control the urticaria. In severe cases, an injection of epinephrine (adrenalin) may be needed. Cortisone may also bring dramatic relief, but its use must be limited to short periods of time.