Hives

Hives
(Urticaria & Angioedema)

Medical Author: Alan Rockoff, MD
Medical Editor: Melissa Conrad Stöppler, MD

• What are hives (urticaria)?
• What causes hives?
• What are the different kinds of hives?
• Ordinary hives
• Symptoms of ordinary hives
• Causes of ordinary hives
• Physical hives
• What is the treatment for hives?
• Conclusion
• Related hives articles:
  Hives - on WebMD

Hives - on eMedicineHealth

What are hives (urticaria)?

Hives (medically known as urticaria) are red, itchy, raised areas of skin that appear in varying shapes and sizes. They range in size from a few millimeters to several inches in diameter. Hives can be round, or they can form rings or large patches. Wheals (welts), red lesions with a red "flare" at the borders, are another manifestation of hives. Hives can occur anywhere on the body, such as the trunk, arms, and legs.

It is estimated that 15% of all people will develop urticaria at some point in their lives. Of those with chronic hives, some 80% are idiopathic, the medical term which means that no cause, allergic or otherwise, can be found.

One hallmark of hives is their tendency to change size rapidly and to move around, disappearing in one place and reappearing in other places, often in a matter of hours. Individual hives usually last two to 24 hours. An outbreak that looks impressive, even alarming, first thing in the morning can be completely gone by noon, only to be back in full force later in the day. Very few, if any other skin diseases occur and then resolve so rapidly. Therefore, even if you have no evidence of hives to show the doctor when you get to the office for examination, he or she can often establish the diagnosis based upon the history of your symptoms. Sometimes it is helpful to bring along a photograph of what your rash looked like at its worst.

Swelling deeper in the skin that may accompany hives is called angioedema. This may be seen on the hands and feet as well as on mucous membranes (with swelling of the lips or eyes that can be as dramatic as it is brief.)

What causes hives?

Hives are produced by histamine and other compounds released from cells called mast cells, which are a normal part of skin. Histamine causes fluid to leak from the local blood vessels, leading to swelling in the skin.

Hives are very common. Although they can be annoying, they usually resolve on their own over a period of weeks, and are rarely medically serious. Some hives are caused by allergies to such things as foods, medications, and insect stings, but the large majority of cases are not allergic, and no specific cause for them is ever found. Although patients may find it frustrating not to know what has caused their hives, maneuvers like changing diet, soap, detergent, and makeup are usually not helpful in preventing hives and for the most part are not necessary.

In rare cases (some hereditary, others caused by bee stings or drug allergy), urticaria and angioedema are accompanied by shock and difficulty breathing. This is called anaphylaxis. Ordinary hives may be widespread and disturbing to look at, but the vast majority of cases do not lead to life-threatening complications.

What does urticaria (hives) look like?

Source: MedicineNet.com
http://www.medicinenet.com/hives/article.htm