Erythema multiforme
Erythema multiforme is a skin reaction to a trigger, almost always an infection. Its lesions are highly characteristic: round patches with concentric rings…
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Medicines commonly prescribed for Erythema multiforme
For informational purposes only. Always consult a doctor before using any medicine.
Dosage form: TABLET, 800 mgActive substance: aciclovirManufacturer: Aristo Pharma Iberia S.L.Prescription requiredDosage form: TABLET, 800 mgActive substance: aciclovirManufacturer: Towa Pharmaceutical S.A.Prescription required
Erythema multiforme is a skin reaction to a trigger, almost always an infection. Its lesions are highly characteristic: round patches with concentric rings that look like a target. The usual form is benign and resolves on its own within a few weeks; what matters is recognising it, finding the trigger and distinguishing it from severe drug reactions that look similar and are emergencies.
How it looks
- round patches 1–3 cm across with three concentric zones: a dark or blistered centre, a paler ring around it and a red outer border;
- they appear symmetrically and start on the hands and feet;
- they spread towards the forearms, legs, face and trunk;
- they favour extensor surfaces: backs of the hands, elbows, knees;
- palms and soles can be involved;
- burning or mild itching rather than pain;
- new lesions keep appearing over several days, and each lasts one to two weeks;
- in the major form there are also painful erosions on the lips, in the mouth, on the eyes or the genitals.
Causes
- herpes simplex virus — by far the most common cause. Lesions appear one to three weeks after a cold sore, which has sometimes gone unnoticed;
- Mycoplasma pneumoniae — particularly in children and adolescents, after a respiratory infection;
- other viral and bacterial infections, and some fungal ones;
- medicines, though less often than commonly believed: anti-inflammatories, antibiotics, antiepileptics;
- vaccines, rarely;
- in a proportion of cases no trigger is identified.
When to see a doctor
- target lesions have appeared;
- there are erosions or blisters on the lips, in the mouth, on the eyes or genitals;
- eating or drinking is difficult;
- there is eye pain or redness — the eyes need specific assessment;
- there is fever and marked malaise;
- the lesions appeared after starting a new medicine;
- the episode is recurring;
- a child has this rash with cough and fever — mycoplasma infection is possible.
Seek urgent care if the skin is painful to touch, peels in sheets, there are extensive blisters, significant involvement of two or more mucous membranes and the person is generally unwell. Those signs point to Stevens-Johnson syndrome or toxic epidermal necrolysis, which are different conditions, almost always drug-induced, and treated in hospital.
How it is diagnosed
By the appearance and distribution of the lesions. The doctor will ask what infections you have had in the past two weeks, what medicines you have taken and whether you have had a cold sore. Blood tests are usually unnecessary; if the picture is unclear, a skin biopsy is taken or herpes and mycoplasma are investigated. If the episode recurs, recurrent herpes is looked for, as that is the most common explanation.
Treatment
The mild form resolves on its own; treatment relieves symptoms and prevents complications.
- treat the trigger: antivirals for active herpes, antibiotics for mycoplasma;
- withdraw the suspected medicine, always on medical advice;
- antihistamines for itching;
- topical corticosteroids for the skin lesions;
- mouthwashes and anaesthetic gels for the mouth, with a soft, cool, non-acidic diet;
- ophthalmology assessment if the eyes are involved: do not wait here, as it can leave lasting damage;
- oral corticosteroids in selected cases, at the doctor's discretion;
- long-term preventive antiviral treatment if episodes recur because of herpes — this is what breaks the cycle;
- fluids and pain relief if swallowing is painful.
What you can do
- keep your fluid intake up, even in small sips or through a straw;
- soft, cool food, avoiding acidic, spicy and very hot items;
- gentle mouth care with a soft brush;
- cool compresses on the lesions;
- sun protection for cold sores if sunlight triggers them;
- write down what happened in the preceding fortnight: infections, medicines, cold sores. That list is the most useful thing you can bring;
- do not scratch.
Course
An episode lasts two to four weeks and leaves no scarring, although dark marks remain and fade over months. Some people have several episodes a year, almost always from recurrent herpes, and in those cases preventive treatment works well.
Common questions
Is it contagious? Erythema multiforme is not. The infection that triggered it, such as herpes, may be.
Is it an allergy? Not in the usual sense. It is an immune reaction, and in most cases the trigger is an infection rather than a drug.
Is it the same as Stevens-Johnson syndrome? No. They are different processes with different causes and severity. That is why recognising the warning signs matters.
Will it scar? Not on the skin. Lasting damage is possible if the eyes are affected and not treated.
Can it be prevented? If herpes is the cause, yes — by treating the herpes preventively.
Online consultation
In an online consultation the doctor reviews photographs and the distribution of the lesions, works with you to find the trigger among recent infections and medicines, recognises the signs that require hospital care, and — if episodes recur — arranges preventive treatment for herpes.
This material is for information only and does not replace a medical consultation.
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Reviewed on Jul 20, 2026
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