Erythema multiforme is a skin reaction (usually mild) caused by an allergy or infection. The rash tends to flare up and go away on its own, but you may need treatment for some of the symptoms.
The skin disorder gets its name from the appearance of the rash:
Most people with erythema multiforme (EM) just have a few spots that clear up quickly, but there is also a rare and more severe form that can affect the mouth, genitals and surface of the eyes, and can be life-threatening.
Erythema multiforme is usually seen in children and young adults (aged 20-40), especially males. It does not appear to run in families.
Symptoms of EM depend on the type of disease you have.
If you have the mild form of EM, you may feel perfectly well but just have an uncomfortable rash. It's usually caused by the herpes simplex virus or a bacterial infection (see What triggers it? below).
The spotty rash looks a bit like hives and usually erupts over 24 hours, starting on the hands and feet and spreading to the limbs, upper body and face. It may cause a mild burning or itching feeling.
The spots are small raised areas, some of which then develop into "bulls-eye" or "target lesions" measuring about 1-3cm across – these have a dark red centre with a blister or crust, surrounded by a paler pink ring with a bright red outermost ring.
The rash usually fades over two to four weeks, but can return.
This rare form of the disease is much more severe and sometimes life-threatening. It's usually caused by a reaction to medication rather than an infection.
The rash is made up of bigger spots that may fuse to produce large red areas. They may blister to reveal raw, painful sores. You might also have:
Most cases of EM, especially EM minor, are caused by a viral infection – usually the herpes simplex (cold sore) virus. The cold sore virus lies dormant and tends to be reactivated by certain triggers. This explains why EM can flare up repeatedly.
Children with EM will usually develop a cold sore a few days before the rash starts.
The second most common trigger is a chest infection caused by mycoplasma bacteria.
Medication can sometimes trigger the more severe type of EM. Medicines that can cause EM include:
Experts believe that an EM reaction involves damage to the tissues and blood vessels of the skin.
If you think you have EM, see your doctor immediately. Your doctor may be able to diagnose EM just by looking at your skin.
If your doctor is uncertain of the diagnosis, you'll be referred to a skin specialist (dermatologist).
Treatment aims to control the illness that is causing the EM, prevent infection and manage the symptoms.
Your doctor may advise you to stop taking medication that may be triggering the EM. Don't stop any medication without speaking to your doctor first.
Symptoms can be treated with:
If you have severe EM, you may need to stay in hospital and be treated in an intensive care unit or a burns unit.
You may also need:
Possible complications of EM include:
Occasionally, internal organs may be affected, causing inflammation of the heart (myocarditis), lungs (pneumonia), kidneys (nephritis) or liver (hepatitis).
Mild cases of EM usually get better in two to three weeks using simple lotions or steroid cream, but the disease can return (usually when the cause is the herpes simplex virus). If this is the case, you may be prescribed a small daily dose of a drug to suppress the herpes simplex virus for several months.
More severe cases may take up to six weeks to get better. A few people are left with scars on their skin after the rash clears up and damaged vision if their eyes have been effected.
Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.