Erythema multiforme is a skin disorder due to an allergic reaction or infection.

Erythema multiforme is a type of allergic reaction that occurs in response to medications, infections, or illness. Medications include:

• Barbiturates
• Penicillins
• Phenytoin
• Sulfonamides

Infections include:

• Herpes simplex
• Mycoplasma

Most erythema multiforme is associated with herpes simplex or mycoplasma infections.

The exact cause is unknown. The disorder is believed to involve damage to the blood vessels of the skin, followed by damage to skin tissues.

Some forms of this condition are more severe than others. Erythema multiforme minor is not very serious. Erythema multiforme major is more severe. The more severe form is usually caused by reactions to medications, rather than infections.

Erythema multiforme occurs primarily in children and young adults.