ur·ti·car·i·a / ˌərtiˈke(ə)rēə/ • n. Med. a rash of round, red welts on the skin that itch intensely, sometimes with dangerous swelling, caused by an allergic reaction, typically to specific foods. Also called nettlerash or hives.

urticaria (nettle rash, hives) (er-ti-kair-iă) n. an itchy rash resulting from the release of histamine by mast cells. Individual swellings (weals) appear rapidly and resolve spontaneously within hours. Angio-oedema occurs when the weals involve the lips, eyes, or tongue, which may swell alarmingly and constitute a medical emergency. acute u. a common and immediate response to such allergens as seafood or strawberries. cholinergic u. a condition in which very small weals are brought on by heat, exercise, or emotion. chronic u. a condition that is not allergic and may persist for years.

urticaria See hives