Hives Overview from the Dermatology Department
Urticaria, also known as hives, is an outbreak of swollen, pale red bumps or patches (wheals) on the skin that appear suddenly as a result of the body's adverse reaction to certain allergens or for unknown reasons. Hives usually cause itching but may also burn or sting. They can appear anywhere on the body including the face, lips, tongue, throat or ears. Hives vary in size (from a pencil eraser to a dinner plate) and may join together to form larger areas known as plaques. They can last for hours or up to 3 to 4 days before fading.
Angioedema is tissue swelling similar to urticaria, but the swelling occurs beneath the skin instead of on the surface. Angioedema is characterized by deep swelling around the eyes and lips and sometimes of the genitals, hands and feet. Angioedema generally lasts longer than urticaria, but the swelling usually goes away in less than 24 hours.
Occasionally, severe, prolonged tissue swelling can be disfiguring. Rarely, angioedema of the throat, tongue or the lungs can block the airways, causing difficulty breathing and become life-threatening.
Causes of hives and angioedema
Hives and angioedema form when blood plasma leaks out of small blood vessels in the skin because a chemical called histamine is released. Histamine is released from mast cells along the blood vessels in the skin. Allergic reactions, chemicals in foods, insect stings, sunlight exposure or medications can cause histamine release. Sometimes it's impossible to find out why hives have formed.
Types of urticaria and angioedema
- Acute Urticaria: hives lasting less than six weeks. The most common causes are foods, medications, latex or infections. Insect bites and internal disease may also be responsible. The most common foods that cause hives are nuts, chocolate, fish, tomatoes, eggs, fresh berries and milk. Fresh foods cause hives more often than cooked foods. Food additives and preservatives may also be the cause. Medications that can cause hives and angioedema include aspirin and other nonsteroidal anti-inflammatory medications such as ibuprofen, high blood pressure medications (ACE inhibitors) or pain-killers such as codeine.
- Chronic Urticaria and Angioedema: hives lasting more than six weeks. The cause of this type of hives is usually more difficult to identify than that of acute urticaria. In patients with chronic urticaria, the cause is found in only a small number of patients and is unknown for more than 80 percent of patients. Chronic urticaria and angioedema can effect other internal organs (such as the lungs and gastrointestinal tract), and can cause symptoms of shortness of breath, vomiting, and diarrhea.
- Physical Urticaria: hives caused by direct physical stimulation of the skin such as cold, heat, sun exposure, vibration, pressure, sweating, exercise and others. The hives usually occur at the site of direct stimulation and rarely, appear on other skin areas. Most of the hives appear within one hour after exposure.
- Dermatographism: hives that form after firmly stroking or scratching the skin. These hives can also occur along with other forms of urticaria. This type of hives is considered a normal variant of the skin.
Diagnosis of hives and angioedema
Your doctor will need to ask many questions in an attempt to find the possible cause. Since there are no specific tests for hives or the associated swelling of angioedema, testing will depend on your medical history and a thorough examination by your dermatologist. Skin tests may be performed to determine the substance that you are allergic to. Routine blood tests are done to determine if a systemic illness is present
Treatment of hives and angioedema
The best treatment for hives and associated swelling is to identify and remove the trigger. This is not an easy task. Antihistamines are usually prescribed by your dermatologist to provide relief from symptoms. Antihistamines work best if taken on a regular schedule to prevent hives from forming.
Chronic hives may be treated with antihistamines or combination medications. When antihistamines do not provide relief, oral corticosteroids may be prescribed. For severe hive or angioedema outbreaks, an injection of epinephrine (adrenaline) or a cortisone medication may be needed.