Erythema multiforme is an immune-mediated reaction that involves the skin and sometimes the mucosa. Classically described as target-like, the erythema multiforme lesions can be isolated, recurrent, or persistent. Most commonly, the lesions of erythema multiforme present symmetrically on the extremities (especially on extensor surfaces) and spread centripetally. Infections, especially herpes simplex virus and Mycoplasma pneumoniae, and medications constitute most of the causes of erythema multiforme; immunizations and autoimmune diseases have also been linked to erythema multiforme. Erythema multiforme can be differentiated from urticaria by the duration of individual lesions. Erythema multiforme lesions are typically fixed for a minimum of seven days, whereas individual urticarial lesions often resolve within one day. Erythema multiforme can be confused with the more serious condition, Stevens-Johnson syndrome; however, Stevens-Johnson syndrome usually contains widespread erythematous or purpuric macules with blisters. The management of erythema multiforme involves symptomatic treatment with topical steroids or antihistamines and treating the underlying etiology, if known. Recurrent erythema multiforme associated with the herpes simplex virus should be treated with prophylactic antiviral therapy. Severe mucosal erythema multiforme can require hospitalization for intravenous fluids and repletion of electrolytes.