Hives, or urticaria, are welts on the skin that often itch. These welts may appear anywhere on the skin and vary in size and shape. Most often, your hives will go away in 24 hours or less. New hives may appear as older ones fade, so hives may last for a few days or longer. A course of hives generally lasts less than 6 weeks. If hives last more than 6 weeks, they are called chronic hives. When larger welts occur deeper in the skin, the term is angioedema. This can occur with or without hives, and often causes the eyelids or lips to swell.
Finding the cause of hives, especially chronic hives, can sometimes be difficult. Acute hives often result from an allergic reaction. Things that trigger an allergic reaction include foods (citrus fruits, milk, eggs, tree nuts, and shellfish are common culprits), medications, insect bites, pollen, latex allergies, and allergy shots. Other causes include infections, illnesses, exposure to sun, heat, cold or water, exercise, stress, pressure on the skin, and contact with chemicals.
Treatment depends on the type of urticaria, its severity and how long it has been present. If a medicine is thought to be the cause, it should be stopped. The most common treatment for hives are non-sedating (does not cause drowsiness) antihistamines. Antihistamines relieve symptoms, such as itching. Occasionally, you may need a combination of multiple antihistamines to control the hives.