Urticaria multiforme in a 2-year-old girl.

We describe a 2-year-old girl who presented to the emergency department for a 2-day history of a rapidly spreading, pruritic, erythematous rash. There were large polycyclic annular erythematous wheals on the face, trunk, and extremities. Urticaria multiforme was diagnosed. Systemic antihistamine therapy greatly regressed the dermal lesions in 24 hours. Urticaria multiforme, a benign cutaneous hypersensitivity reaction, is commonly misdiagnosed as erythema multiforme or a serum sickness-like reaction. Our case highlights the importance of differentiating urticaria multiforme to prevent unnecessary tests and provide proper treatment.