Usually the result of an allergic response to insect bites or food or drugs

• Rash old city teacher primarily in charge of some music?
• Hives, medically
• An itchy skin eruption characterized by weals with pale interiors and well-defined red margins
• The Hives' original song about facial twitch

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Urticaria \Ur`ti*ca"ri*a\, n. [NL. See Urtica .] (Med.) The nettle rash, a disease characterized by a transient eruption of red pimples and of wheals, accompanied with a burning or stinging sensation and with itching; uredo.

WordNet Word definitions in WordNet
n. an itchy skin eruption characterized by weals with pale interiors and well-defined red margins; usually the result of an allergic response to insect bites or food or drugs [syn: urtication , hives , nettle rash ]

Wiktionary Word definitions in Wiktionary
n. (lb en diseases) itch, swollen, red areas of the skin which can appear quickly in response to an allergen or due to other conditions

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
"nettle-rash," medical Latin, from Latin urtica "nettle, stinging nettle" (figuratively "spur, incentive, stimulant), from urere "to burn," from PIE root *eus- "to burn" (see ember ) + abstract noun ending -ia . Related: Urticarial .