Erythema Multiforme

Medical Reviewer

Erythema multiforme (EM) refers to a form of skin rash. The term 'multiforme' refers to the fact that its appearance can vary on the person and may vary from person to person. The main cause is the herpes virus, either as a cold sore, genital herpes, or as a hidden infection.

There are two forms of EM. EM minor, the form associated with herpes,  is not serious, whereas EM major (also known as Stevens-Johnson syndrome) is. EM major is nearly always related to severe reactions from drugs such as penicillin, phenytoin or barbiturates. However, EM minor accounts for roughly 80 per cent of all cases.

Nearly half of all cases of herpes related EM occur in people under the age of 20. Men appear to be slightly more prone than women.

EM minor appears as an itchy red and blotchy rash. The rash usually appears on the hands and forearms but may also appear on the face, legs and feet. The lesions themselves may appear as a bulls-eye shaped raised lump that seems to have three distinct rings. The inner 'ring' may be a fluid-filled blister. Painful blisters may also appear in and around the mouth. Once the eruption begins it may last anything from 2-4 weeks.

Many people with herpes may never experience EM. Those who do may have a single eruption. A very few may be unfortunate enough to have recurrences as many as six times a year for up to 10 years.

The rash will clear by itself and therefore no treatment is needed. If itching is a problem the doctor may prescribe an antihistamine. Oral Aciclovir may be prescribed to help prevent recurrences.