A red rash usually forming concentric rings with purplish centres
- Most common in children and young adults
- More common in males
- Genetics and lifestyle are not significant factors
Erythema multiforme develops rapidly and is characterized by distinctive red spots that grow bigger over a few days. The rash is widespread, and often includes the palms of the hands and the soles of the feet. It may affect the mucous membranes, such as the lining of the mouth and nose. The rash is most common in young people and affects more males than females. The disorder is not contagious and is usually mild, although a serious form sometimes occurs.
In most cases, the cause of erythema multiforme is unknown, but the rash can be triggered by infection with a virus such as herpes simplex, the virus that produces cold sores. Other factors that can trigger the rash include taking certain drugs, such as the antigout drug allopurinol, penicillins (see Antibiotic drugs), and phenytoin (see Anticonvulsant drugs). Erythema multiforme can also be caused by cancer or by radiotherapy.
What are the symptoms?
The symptoms, which develop suddenly, may include:
Many small, red spots distributed symmetrically over the body. The spots usually enlarge to form red rings with purplish centres, called target lesions. The lesions may blister in the middle.
Itching of the affected area.
Painful, inflamed lesions within the mouth and nose.
Fever, headache, and sore throat.
In rare instances, most of the skin and mucous membranes throughout the body become severely inflamed and ulcerated. Such cases require emergency treatment because the condition may be life-threatening if it is left untreated.
What might be done?
Your doctor will probably make a diagnosis from the appearance of the rash. If the rash appeared shortly after you started taking a prescribed drug, the doctor may prescribe an alternative treatment. If itching is a problem, he or she may suggest an oral antihistamine (see Antipruritic drugs). In the case of severe erythema multiforme, particularly if the mouth is inflamed, you may need treatment in hospital; intravenous fluids, painkillers, and corticosteroids may be given in an intensive therapy unit.
Erythema multiforme usually disappears over a few weeks. However, there is a possibility that it may recur. If a drug is thought to be the cause, you should avoid taking it in future.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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