Erythema Multiforme

What is Erythema Multiforme

Erythema multiforme is a rash that usually occurs on the skin, but can also occur on the lips and on the inside of the mouth. It is usually a mild condition that goes away on its own.

It most often affects young adults and children. The rash shows up suddenly and often lasts 1–4 weeks. In some cases, the rash may come back again after clearing up.

What are the causes?

The cause of erythema multiforme may be an overreaction by the body’s immune system to a trigger.

Common triggers include:

  • Infection, most commonly by the cold sore virus (human herpes virus, HSV), bacteria, or fungus.

Less common triggers include:

  • Medicines.
  • Other illnesses.

In some cases, the cause may not be known.

What are the signs or symptoms?

The rash from erythema multiforme shows up suddenly. It may appear days after exposure to the trigger. It may start as small, red, round or oval marks that become bumps or raised welts over 24–48 hours. These bumps may resemble a target or a “bull’s eye.” These can spread and be quite large (about 1 inch [2.5 cm]). There may be mild itching or burning of the skin at first.

These skin changes usually appear first on the backs of the hands. They may then spread to the tops of the feet, the arms, the elbows, the knees, the palms, and the soles of the feet. There may be a mild rash on the lips and lining of the mouth. The skin rash may show up in waves over a few days.

It may take 2–4 weeks for the rash to go away. The rash may return at a later time.

How is this diagnosed?

Diagnosis of erythema multiforme is usually made based on a physical exam and medical history. To help confirm the diagnosis, a small piece of skin tissue is sometimes removed (skin biopsy) so it can be examined under a microscope by a specialist (pathologist).

How is this treated?

Most episodes of erythema multiforme heal on their own. Treatment may not be needed. Your health care provider will recommend removing or avoiding the trigger if possible. If the trigger is an infection or other illness, you may receive treatment for that infection or illness. You may also be given medicine for itching. Other medicines may be used for severe cases or to help prevent repeat bouts of erythema multiforme.

Follow these instructions at home:

  • Take medicines only as directed by your health care provider.
  • If possible, avoid known triggers.
  • If a medicine was your trigger, be sure to notify all of your health care providers. You should avoid this medicine or any like it in the future.
  • If your trigger was a herpes virus infection, use sunscreen lotion and sunscreen-containing lip balm to prevent sunlight triggered outbreaks of herpes virus.
  • Apply moist compresses as needed to help control itching. Cool or warm baths may also help. Avoid hot baths or showers.
  • Eat soft foods if you have mouth sores.
  • Keep all follow-up visits as directed by your health care provider. This is important.

Contact a health care provider if:

  • Your rash shows up again in the future.
  • You have a fever.

Get help right away if:

  • You develop redness and swelling on your lips or in your mouth.
  • You have a burning feeling on your lips or in your mouth.
  • You develop blisters or open sores on your mouth, lips, vagina, penis, or anus.
  • You have eye pain, or you have redness or drainage in your eye.
  • You develop blisters on your skin.
  • You have difficulty breathing.
  • You have difficulty swallowing, or you start drooling.
  • You have blood in your urine.
  • You have pain with urination.
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