Erythema multiforme is a skin disease that occurs mostly in children and yound adults. It is thought to be due to a hypersensitive allergic reaction to something that leads to problems with blood vessels in the skin. Most cases are associated with herpes or mycoplasma infections.

The most common symptom is that of skin lesions. In some cases systemic problems develop that affect the whole body. In the variant known as Stevens Johnson syndrome these are especially severe. Toxic epidermal necrolysis is especially severe. It involves the death of the skin and mucous membranes.The usual location for these lesions are the hands, arms, legs and face. The trunk is typically not affected. Lesions may coalesce to cause more serious skin disorders.

In most cases the syndrome is not severe, and is cured after a few week s of treatment, in which the main aims are to prevent secondary infection and stop the skin drying out. In the more severe cases permanent scarring, or even death may occur.