Hives are common and affect more than 40 million people in the U.S. They present themselves as welts on the skin, occurring individually or clustering together to form one large welt. Hives are most commonly caused by allergic reactions, although they may also be evidence of an infection or underlying illness. Some people even develop hives as a result of stress or exposure to the sun.
Antihistamines, cortisones and anti-inflammatory medicines are most often used to treat hives, although persistent, unexplained hives require further examination via blood and allergy testing. Hives are generally not dangerous, but in some cases, hives may occur deep within the skin, causing the airways to swell and restrict breathing. If this occurs it is important to seek immediate emergency attention.