Hives are raised, red, and extremely itchy “welts” (called wheals) on the skin surface that can last minutes to hours. In medical writing, hives are often referred to as urticaria.
Hives are a common problem that can disrupt sleep, school, and work. They appear quickly when special skin cells called mast cells are triggered to release chemicals that cause the redness, itching, and swelling. Hives can be part of a severe, whole-body allergic reaction called anaphylaxis.
Most cases of short-lasting hives are triggered by allergic reactions, medications, or viral infections. Allergic responses to foods, bee stings, medications, or airborne substances can all cause hives. Physical factors such as pressure, cold, heat, or vibration can also provoke urticaria in certain people. Dermatographism (Latin for “skin writing”) refers to hives that pop up for only minutes after a scratch or irritation to the skin.
It is possible to have hives lasting for weeks or months. This “chronic urticaria” is usually not due to a particular trigger, but instead it can result from abnormal immune reactions involving the mast cell. The severity of chronic hives can be affected by other factors such as stress, medications, temperature, and illnesses.