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.)
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