The typical target lesion (also called iris lesion, bulls-eye lesion or cockade) of erythema multiforme has a sharp margin, regular round shape and three concentric color zones. Lesions can arise on any sites, including face, upper chest, back, arms, legs, hands, feet and mucous membranes (such as the lips).

Your dermatologist will diagnosed erythema multiforme looking at your skin, although a biopsy may be required to exclude other conditions.