Causes of Erythema Multiforme
Infections usually cause erythema multiforme, and certain medications cause it less commonly. Erythema multiforme is considered a hypersensitivity reaction, meaning the immune system overreacts to a trigger, leading to inflammation and the characteristic rash.
Infectious Triggers
The majority of cases—particularly mild ones—are caused by infections. The most frequent culprits include:
Herpes simplex virus (HSV) – The leading cause, especially in recurring cases. The rash often appears a few days after a cold sore or genital herpes flare-up.
Mycoplasma pneumoniae – A respiratory infection that is more commonly linked to erythema multiforme major.
Other viruses, such as Epstein-Barr virus, cytomegalovirus, and HIV, may occasionally trigger the condition.
Fungal and bacterial infections – Though less common, can sometimes play a role.
Medication Reactions
In some people, drugs can trigger erythema multiforme. Common offenders include:
Antibiotics, especially sulphonamides and penicillins
Non-steroidal anti-inflammatory drugs (NSAIDs)
Anticonvulsants, such as phenytoin and carbamazepine
Barbiturates
Drug-related cases are more often associated with erythema multiforme major and may take longer to resolve. If suspected, the medication should be stopped immediately under medical supervision.
Other Triggers
Rare causes include:
Vaccinations
Radiation therapy
Underlying autoimmune conditions
Causes of Erythema Multiforme In South Africa
In South Africa, limited access to viral testing may make it difficult to confirm the exact cause of erythema multiforme. Many rural clinics may not associate skin eruptions with herpes or pneumonia. Education of frontline health workers is key to identifying patterns and treating the condition early.
Prevention is possible in recurring cases by suppressing the triggering infection—often with antiviral medication in the case of HSV.
Recognising the causes of erythema multiforme helps guide both treatment and prevention. Identifying the trigger allows for more targeted therapy and reduces the risk of recurrence.
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