What is erythema multiforme?
Erythema multiforme (EM) is a hypersensitivity reaction that tends to develop suddenly. It is predominantly seen in young adults. It is rarely seen in children but can occur in any age group.
The sudden development of few spots characterizes erythema multiforme to hundreds of red spots. The spots usually begin on feet and hands and spread upwards towards the trunk. The face is often involved.
Over time these spots change to plaques (raised patches) and then typical target-shaped lesions, which have a dusky red center, a paler area around this, and then a dark red ring round the edge. Sometimes the center of the target can be crusted or blistered.
The targets can be different shapes and sizes, hence the Latin name: erythema (redness) multi (many), forme (shapes). Erythema multiforme is usually mild – ‘erythema multiforme minor’ – with only skin involvement, and clearing up in days to weeks.
There is also a rare but more severe type, ‘erythema multiforme major,’ which has similar skin features to EM minor. However, additionally, there is the involvement of one or more mucosal membranes (e.g., the lips, the inside of the mouth, the windpipe, the gullet, the anus or genital area, and the eyes) and usually some associated symptoms, such as fever or joint pain.
What causes erythema multiforme?
The cause of erythema multiforme is not fully understood. It is thought to be a skin reaction that occurs following exposure to a trigger or irritant.
It is thought that around 90% of cases are caused by infections such as the herpes simplex virus (the cold sore virus) or mycoplasma bacteria, which causes pneumonia.
Medications are a less common cause of erythema multiforme. When medications are the cause, it is more likely that an individual will develop a worse form of the rash called erythema multiforme major.
Drugs that have been identified as causing EM to include non-steroidal anti-inflammatory drugs (given for joint and muscle pain), antibiotics and anticonvulsants (used to treat epilepsy) as well as statins, immunotherapy drugs, and vaccinations.
What are the symptoms of erythema multiforme?
The symptoms will vary with the severity of the rash. If it is mild, you may feel perfectly well, and your rash may be asymptomatic or associated with a mild itch or burning sensation.
If your erythema multiforme is more severe (erythema multiforme major), you may have a fever and a headache and feel unwell for a few days before the rash appears.
Blisters on your skin may rupture and leave painful raw areas. If your eyes are affected, you may become sensitive to light and notice the blurring of your vision.
Raw areas inside the mouth can make it hard to eat and drink. Genital soreness can interfere with passing urine.
How does erythema multiforme look like?
In erythema multiforme minor:
- The spots usually develop over the course of 3 – 4 days, starting on the hands and feet, and then spreading up the limbs to the trunk and face.
- At first, the spots are small, round, slightly raised red areas, some of which turn into the ‘target lesions’ described above. Small blisters form in the center of some of the targets
- The rash usually fades over 2 – 4 weeks.
- There are usually no complications from this type of erythema multiforme.
- Recurrences are common in some individuals, especially where the herpes simplex virus is the cause. In erythema multiforme major: ● You may feel ill and have a high temperature.
- The spots are usually larger and run into each other more than those of erythema multiforme minor. ‘Target lesions’ can usually still be seen.
- Large blisters may form, and then burst to leave red oozing areas.
- Your lips may be covered with crusts, large raw areas may appear inside your mouth, and your eyes may swell up and turn red.
- Complications are rare and are mainly from scars of the skin in the mouth or the eyes.
How is erythema multiforme diagnosed?
There are no specific tests for erythema multiforme. The diagnosis is usually made by identifying the characteristic rash on the skin and a story of recent exposure to one of the possible causes mentioned above.
Occasionally it is necessary to do a skin biopsy (to remove a small sample of skin under a local anesthetic) to confirm the diagnosis under the microscope and exclude other possibilities.
Can erythema multiforme be cured?
Most patients with erythema multiforme recover completely; however, there can be a risk of further attacks, particularly following cold sores.
How can erythema multiforme be treated?
Your doctor will look for known causes for the skin condition. If a particular medication is suspected, it should be stopped straight away.
If an infectious cause is identified, then treatment specifically for this (where it exists) should be given.
The treatment will then depend on the severity and symptoms of the erythema multiforme:
- Mild rashes will need topical treatment.
- Severe rashes can be life-threatening. Patients may need to be nursed in the hospital for dressings of the skin, pain relief, and fluid and electrolyte replacement.
Antibiotics may be needed if the damaged skin is infected. An eye specialist is required if the eyes are affected. Oral steroids are sometimes given, especially in the early stages. Other immunosuppressant medications may also be used in cases that are difficult to treat.
- Recurrent attacks may be a problem that may need prophylaxis for many months.
Self-care (What can you do?)
- If you have had one attack of erythema multiforme, remember there is a risk that you will have another.
- If a medication was suspected to be the cause, this must be avoided in the future.
- If your attacks follow cold sores, you may want to ask your doctor about taking antiviral tablets for the long-term.