Urticaria (hives) are localized, pale, itchy, pink wheals (swellings) that can burn or sting. They may occur singularly or in groups on any part of the skin; they are part of an allergic reaction and are very common. Approximately 10-20 percent of the population will have at least one episode in their lifetime. Most episodes of hives disappear quickly in a few days to a few weeks. Occasionally, a person will have them for many months or years. New hives may develop as hold ones fade. Hives can vary in size from as small as a pencil eraser to as large as a dinner plate, and may join to form even larger swellings.