Hives are small areas of swelling that occur on the skin surface in random areas on the body. Other commonly known names for hives include welts or urticaria. The medical term for hives is wheals. Hives typically appear very suddenly and may be pink or red with a raised surface around the edges with associated itching. The vast majority of hives last for a few minutes to a few hours, but in some cases can last for days, despite treatment. Rarely, hives can progress to a more significant allergic reaction that includes swelling of the tongue and throat with difficulty breathing, in which case they are potentially life-threatening.