Causes of erythema multiforme

The cause oferythema multiforme is often unclear, but some cases are the result of a reactionto an infection or medication.

The condition can't be passed from person to person.


Most cases are caused by a viral infection often the herpes simplex (cold sore) virus. This virus usuallylies inactive in the body, but it can become reactivated from time to time.

Some people willget a cold sore a few days before the rash starts.

Erythema multiforme can also be triggered bymycoplasma bacteria, a type of bacteria that sometimes cause chest infections .


Medication can occasionally cause the more severeform oferythema multiforme. Possible medication triggersinclude:

  • antibiotics ,such assulfonamides, tetracyclines, amoxicillin and ampicillin
  • non-steroidal anti-inflammatory drugs (NSAIDs) , such as ibuprofen
  • anticonvulsants (used to treat epilepsy ), such as phenytoin and barbiturates
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Medically Reviewed by a doctor on 21 Dec 2018