What is "erythema multiforme"

n. a red rash caused by hypersensitivity to a drug or disease or other allergen

Erythema multiforme is a skin condition of unknown cause; it is a type of erythema possibly mediated by deposition of immune complexes (mostly IgM-bound complexes) in the superficial microvasculature of the skin and oral mucous membrane that usually follows an infection or drug exposure. It is an uncommon disorder, with peak incidence in the second and third decades of life. The disorder has various forms or presentations, which its name reflects (multiforme, "multiform", from multi- + formis). Target lesions are a typical manifestation. Two types, one mild to moderate and one severe, are recognized ( erythema multiforme minor and erythema multiforme major).