Erythema multiforme (EM) is a serious inflammatory skin eruption (rash) caused by allergic reactions to many different things, including prescription and over-the-counter drugs. It can affect people of all ages and is often more severe in children and young adults. Erythema multiforme often starts as a red rash on the palms, soles, and back of the hands. It can spread to the trunk, face, and mouth in severe cases. Some people only have erythema multiforme in the mouth. As the skin lesions age, they often look like small targets with purple to dusky centers surrounded by red rings. The condition can be associated with fever, muscle aches, and not feeling well.

Most cases of erythema multiforme completely recover. There may be dark marks for a few months when the patches clear up. Sometimes, the condition recurs, particularly if the cold sore virus was the cause. However, sometimes the disease can be severe enough that the person needs to be hospitalized. Erythema multiforme has been so named because of the “multiple forms” it appears in.