3 Hives are itchy, pinkish, localized swellings of the skin that usually last a few hours before fading. Urticaria or hives as it is commonly called, is an itchy rash consisting of localized swellings of the skin that usually last for a few hours before fading away. When urticaria develops around loose tissues of the eyes or lips, the affected area may swell excessively. Urticaria results from some changes in the small blood vessels of the skin. Such changes are brought about by the release of some substances in the body, the commonest of which is histamine.
Histamine is released from cells called mast cells by either an allergic or non-allergic reaction.
Acute urticaria, which can last from a few hours to as long as a week is usually caused by drugs, specific foods or a viral infection. Sometimes, no cause can be detected. Hives may appear within minutes or several hours after ingestion of the food depending on its rate of absorption. However, any drug should be suspected even if it has been taken for a long time without ill effects previously. Drugs commonly cause acute urticaria but they may also aggravate chronic urticaria.