Medical Definition of Urticaria
Urticaria: Another name for hives. Raised, itchy areas of skin that are usually a sign of an allergic reaction. Hives can be rounded or flat-topped but are always elevated above the surrounding skin. They reflect circumscribed dermal edema (local swelling of the skin). The hives are usually well circumscribed but may be coalescent and will blanch with pressure.
The hives typically last less than 4 hours but an individual lesion may last for up to 24 hours and the whole process may stay for days or weeks. Approximately 20% of the population has experienced a bout of urticaria.
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