Hives

Hives, also known as urticaria, is a condition in which swollen, red, itchy areas appear on the skin. It is usually due to an allergic reaction from eating certain foods or taking certain medications. Hives vary in size from less than an inch to a few inches. They may be on one area of the body or all over the body. They can last minutes to hours, or even several days before fading.

Angioedema is an allergic reaction similar to hives, but it causes swelling deeper in the layers of the skin. It commonly affects the hands, feet, genitals and face (lips and eyes). It generally lasts longer than hives (which can occur simultaneously) but the swelling usually goes away in 24 hours. In rare cases, angioedema may involve the throat and tongue, blocking the airway and causing breathing difficulty. This can become a life-threatening emergency.

Hives and angioedema occur when histamine is released from special cells found along the skin’s blood vessels. In response to histamine, plasma leaks out from these blood vessels in the skin. Allergic reactions to things like foods, medicines, insect stings and sunlight exposure can cause histamine release. Sometimes it is impossible to determine exactly why hives have formed.

• Acute urticaria and/or angioedema are hives or swelling lasting less than six weeks. The most common causes are foods, medicines, latex or infections. Foods that commonly cause hives are milk, eggs, soy, wheat, fish, shellfish and peanuts. Medicines that can cause hives include penicillin, sulfa medications, anti-seizure medications and non-steroidal anti-inflammatory drugs (NSAIDs, such aspirin and ibuprofen).
• Chronic urticaria and/or angioedema are recurrent hives, lasting longer than six weeks. The cause is usually more difficult to identify. Causes may be similar to acute urticaria, but may also include autoimmunity, viral infections and malignancy.
• Physical urticaria is hives caused by direct physical stimulation of the skin. Common causes are exposure to sunlight, heat, cold air or water, vibration, pressure, sweating and exercise.
• Dermatographism is hives caused by scratching the skin, continual stroking of the skin or wearing tight-fitting clothes that rub the skin. These hives may be found in conjunction with other types of hives.
• Hereditary angioedema is a rare form of angioedema passed on in families. It can cause painful, non-itchy swelling of the skin, and it may involve the face, extremities, genitals, tongue and throat.

A diagnosis is usually made based on a complete medical history and physical examination. There are no specific tests for hives or angioedema. Skin testing may be performed to identify allergens. Routine blood testing may be done to determine whether any other illnesses are causing hives and/or angioedema.

Avoidance of the allergen is the best treatment. If it is caused by a medication, strict avoidance is necessary.

Physicians may recommend antihistamines to decrease histamine release, which can lessen the symptoms of hives and/or angioedema. They may be prescribed on a regular schedule to prevent symptoms. Chronic hives may be treated with antihistamines or a combination of medications. For severe hives and angioedema, an injection of epinephrine may be needed.