| Definition: | Hives are raised, often itchy red welts on the surface of the skin. They can be an allergic reaction to food, medicine, or other substance.
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| Alternative Names: | Urticaria
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| Causes, incidence, and risk factors: | Hives are very common, especially in people who have experienced other allergic reactions, including hay fever and angioedema. The welts occur on the surface of the skin, usually in batches. The release of histamine and other chemicals into the bloodstream (part an allergic response) causes the itching, localized swelling, and other symptoms.
Many substances, called allergens, can trigger an allergic response resulting in hives. Common allergens include:
- Medications
- Foods (such as berries, shellfish, fish, nuts, eggs, milk, and others)
- Pollen
- Animal dander (especially cats)
- Insect bites
Hives may also develop after infections or illness (including autoimmune diseases, leukemia, and others). There seems to be a hereditary tendency toward the development of hives.
Some less common causes of hives include:
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