Erythema multiforme is a skin rash. It's caused by a hypersensitivity reaction. Many things can cause the reaction. These include a virus, bacterium, fungus, medicine, vaccine, or food. It's most often linked with the herpes virus. A severe form of erythema multiforme called Stevens-Johnson syndrome (erythema multiforme major) is most often caused by medicines. This is a very rare form of erythema multiforme.
At first, the skin may have round red bumps, fluid-filled blisters, or pimples. Most of these turn into a round circle with a small dark center. A white ring may surround the entire area of the skin. The sores may cause pain, burning, or itching. They occur most often on the forearms, legs, and back of hands and feet. They can spread to the abdomen, back, face, genitals, and mouth in severe cases. You may also have a fever and muscle aches. This condition is not contagious.
Treatment includes finding and removing the cause. If a medicine may be the cause, you will be told to stop taking it. The sores will likely go away in 2 to 4 weeks without treatment. It may take longer in severe cases. The sores may come back. Your doctor may prescribe antihistamine medicine or an antiviral medicine if the cause appears to be herpes. If any sores become infected, an antibiotic may be prescribed.