Urticaria is a very itchy rash commonly known as hives. Urticaria can affect approximately 20% of Americans at some time in their lives. Typically hives are slightly raised red or pale areas on the skin that range in size from pinpoint to many inches in diameter. They can involve any part of the skin, including the face, hand, extremities and trunk. They can occasionally occur in the mouth. Individual hives can join together to form large itchy, red areas that are called “giant hives.” A single hive can disappear within a few hours leaving the skin without a trace, only to be replaced by new hives. If urticaria causes inflammation or discoloration of the skin that lasts more than 24 hours, then an underlying non-allergy related medical problem may be the cause.
Swelling of the deep skin tissue, often associated with hives, is called angioedema. Angioedema occurs in about half of people who have chronic urticaria.