Overview
Hives (urticaria), also known as welts, is a common skin condition with an itchy rash of pink to red bumps that appear and disappear anywhere on the body. An individual lesion of hives typically lasts a few hours before fading away, and new hives can appear as older areas disappear.
Physicians arbitrarily divide hives into acute (new or periodic episodes lasting fewer than 6 weeks) and chronic (periodic episodes lasting more than 6 weeks). Though many people have a single episode of acute hives that goes away within a few days to weeks, some individuals may have chronic hives, periodic (recurrent) attacks of hives that come back over periods of years.
Hives can be triggered by many things, including:
- Medications, especially aspirin, ibuprofen, naproxen, narcotic painkillers, or antibiotics.
- Infections with viruses, bacteria, or fungi.
- Environmental allergies such as insect bites, pollen, mold, or animal dander.
- Physical exposures such as heat, cold, water, sunlight, or pressure.
- Medical conditions such as gland diseases, blood diseases, or cancer.
- Food allergies such as from strawberries, eggs, nuts, or shellfish.
- Stress.
In up to 90% of outbreaks of hives, a trigger is never found despite extensive testing; these cases are referred to as idiopathic urticaria. In approximately 50% of idiopathic urticaria outbreaks, hives are most likely caused by a reaction from the person's own immune system (autoimmune reaction).
