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
(up to 24 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 that persist intermittently for years. More often than not, the offending agent is never identified in those who suffer from chronic hives.
Hives can be triggered by many things, including:
- Medications, especially aspirin, ibuprofen, naproxen, narcotic painkillers, and antibiotics
- Infections with viruses, bacteria, or fungi
- Environmental allergies such as insect bites, pollen, mold, and animal dander
- Physical exposures such as heat, cold, water, sunlight, and pressure
- Medical conditions including some blood diseases and cancer
- Food allergies such as from strawberries, eggs, nuts, and shellfish
- Stress
In many cases, the causative agent is not identified despite extensive testing. This is 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).
