Hives: A raised, itchy area of skin that may be a sign of an allergic reaction. It can be rounded or flat-topped but is always elevated above the surrounding skin. It reflects circumscribed dermal edema (local swelling of the skin). The hives are usually well circumscribed but may be coalescent and will blanch with pressure. A single spot is almost always gone by 24 hours but the process may stay for weeks to months. Approximately 20% of the population has experienced a bout of hives.
The hives are also called urticaria.