ConditionSkin, hair & nails
Erythema Multiforme: Symptoms, Causes and Treatment
Erythema multiforme is an immune skin reaction that causes round, target-shaped spots, mostly on the hands, arms, feet and legs, sometimes with sores in the mouth. Most cases are triggered by the cold sore virus (herpes simplex), and less often by Mycoplasma infection or medicines. The rash usually clears without scarring in 2 to 4 weeks, though it can come back with each cold sore outbreak.
Also called: EM, erythema multiforme minor, erythema multiforme major
At a glance
- What it is
- An immune reaction in the skin causing target-shaped spots and sometimes mouth sores.
- Most common trigger
- Herpes simplex (cold sore) virus, in about 9 out of 10 cases.
- Who gets it
- Mostly young adults aged 20 to 40. It is less common in children.
- How long it lasts
- About 2 to 4 weeks per episode. It heals without scars.
- Treatment
- Symptom relief, mouth care and sometimes steroids. Antiviral medicine prevents herpes-linked recurrences.
When to get help
Call 911 or go to the ER
- Widespread blistering or peeling skin, or skin that hurts to touch (possible Stevens-Johnson syndrome or toxic epidermal necrolysis)
- Rash after starting a new medicine, with fever and sores in the mouth, eyes and genitals
- Inability to drink, with signs of dehydration such as very little urine
See a doctor within a day or two
- Painful red eyes, light sensitivity or eye discharge with the rash
- Mouth sores so painful that eating and drinking are difficult
- Fever, cough and shortness of breath with the rash (possible Mycoplasma pneumonia)
- Any new target-like rash in a child
Book a routine appointment
- Target spots that come back with each cold sore outbreak
- A mild target rash on the hands and arms in an otherwise well adult
Usually safe to manage at home
- Soothing mouth rinses, cool compresses and soft foods once a doctor has confirmed mild erythema multiforme
What is erythema multiforme?
Erythema multiforme (EM) is a hypersensitivity reaction. The immune system reacts to an infection, most often fragments of herpes simplex virus that reach the skin, and attacks skin cells. "Multiforme" refers to the varied appearance of the spots as they evolve.
It comes in two forms:
- EM minor: skin target spots with little or no mouth involvement. The person usually feels well.
- EM major: target spots plus sores on at least one mucous membrane (mouth, lips, eyes or genitals), often with fever and aches.
EM major used to be considered part of the same spectrum as Stevens-Johnson syndrome, but it is now recognized as a separate condition with different triggers and a much better outlook.
Symptoms
The target rash
- Spots appear suddenly, usually over 24 to 72 hours.
- They start on the backs of the hands and tops of the feet, then spread toward the arms, legs and sometimes face. They are often on both sides of the body.
- Typical target lesions are round, under 3 cm (about 1 inch), with three zones: a dark red or blistered center, a pale swollen ring and a red outer ring.
- Spots may burn or itch mildly. They stay in the same place for a week or more.
Mouth and other mucous membranes
In EM major, painful mouth ulcers, crusted bleeding lips, and sore eyes or genitals can occur. Mouth sores can make swallowing difficult.
General symptoms
A mild fever, tiredness and joint aches may come before or with EM major.
Causes
| Trigger | Clues |
|---|---|
| Herpes simplex virus (most common) | Cold sore on the lip, or genital herpes, 3 to 14 days before the rash |
| Mycoplasma pneumoniae | Cough, fever, more mouth involvement, more common in children |
| Medicines (less common) | Rash within days to weeks of starting antibiotics, anticonvulsants or NSAIDs |
| Other infections | Other viruses, fungal infections |
Many people with recurrent EM do not notice a cold sore before each episode, even though herpes is the cause.
Erythema multiforme vs hives vs SJS
| Feature | Erythema multiforme | Hives (urticaria) | SJS / TEN |
|---|---|---|---|
| Shape | Fixed targets with 3 zones | Raised wheals, often with clear centers | Flat, dusky spots that blister and merge |
| Duration of each spot | 1 to 2 weeks | Under 24 hours, then moves | Spreads over days |
| Itch | Mild burning | Very itchy | Painful skin |
| Mouth sores | Sometimes | No | Almost always, severe |
| Skin peeling | No (small blisters only) | No | Yes, can be widespread |
| Main trigger | Herpes virus | Allergy, infection, unknown | Medicines |
Diagnosis
Diagnosis is usually based on the look of the rash and the history. A doctor will ask about recent cold sores, coughs and new medicines. Tests may include:
- A swab of any active cold sore for herpes PCR
- Chest X-ray and blood tests if Mycoplasma is suspected
- A skin biopsy when the diagnosis is unclear
Treatment
There is no treatment that switches off an episode instantly, but care makes it more comfortable and prevents complications.
- Stop any suspected medicine on a doctor's advice.
- Skin: cool compresses, emollients and strong topical steroid creams. Oral antihistamines can ease itch.
- Mouth: antiseptic or anesthetic mouth rinses, soft cool foods, and plenty of fluids. Avoid spicy, salty or acidic foods.
- Severe EM major: a short course of oral steroids is sometimes used, and hospital care for people unable to drink.
- Eyes: any eye involvement needs an eye doctor (ophthalmologist) promptly, as scarring can affect vision.
- Mycoplasma infection: treated with the appropriate antibiotic.
Preventing recurrent erythema multiforme
People with frequent herpes-related episodes can take daily antiviral medicine (such as acyclovir or valacyclovir) for at least 6 months. Starting antiviral treatment at the first sign of a cold sore is less reliable. Sun protection on the lips helps, since sunlight triggers cold sores. Stubborn cases are managed by a dermatologist.
Outlook
Erythema multiforme is self-limiting and usually heals in 2 to 4 weeks, sometimes leaving temporary darker or lighter patches. Recurrences are common with herpes-related EM, often a few times a year, but tend to become less frequent over time. Lasting complications are rare and mostly involve eye scarring in severe cases.
Frequently asked questions
What causes erythema multiforme?
Most cases are an immune reaction to the herpes simplex virus that causes cold sores. Other triggers are Mycoplasma pneumoniae infection, which is more common in children, and less often medicines such as some antibiotics, anticonvulsants and NSAIDs. In some people no trigger is found.
Is erythema multiforme contagious?
No. The rash is an immune reaction and cannot be passed to others by touch. However, an active cold sore that triggered it does carry contagious herpes virus, so avoid kissing and sharing cups or lip balm while a cold sore is present.
How long does erythema multiforme last?
Each episode typically lasts 2 to 4 weeks. New spots appear for about 3 days, then they fade over the following 1 to 2 weeks without scarring. Mouth sores in erythema multiforme major can take a little longer to heal.
What does erythema multiforme look like?
It looks like small bullseye targets: round spots with a dark or blistered center, a pale ring and a red outer edge. They usually start on the backs of the hands and the feet and spread up the arms and legs, often in a symmetrical pattern.
Can erythema multiforme come back?
Yes. Herpes-related erythema multiforme often recurs, sometimes with every cold sore. Daily antiviral medicine taken for several months can greatly reduce or stop recurrences. Talk to your doctor or a dermatologist if you have more than a few episodes a year.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Dermatology: Erythema multiforme
- DermNet: Erythema multiforme
- MedlinePlus: Erythema multiforme
- Merck Manual Professional Version: Erythema Multiforme
- British Association of Dermatologists: Erythema multiforme patient information leaflet