Erythema multiforme

Erythema multiforme is a hypersensitivity reaction characterised by target lesions. Lesions tend to start distally and spread proximally. 

It most commonly affects those aged 20 to 40. 

Causes include: 
  • Infections – account for 90% of cases 
    • Herpes simplex – commonest infective cause - infection precedes erythema multiforme by up to 2 weeks.
    • Mycoplasma pneumoniae 
    • Fungal infections 
    • Orf 
    • CMV 
    • Herpes varicella zoster 
    • Viral vaccines 
  • Medications 
    • Penicillin 
    • NSAIDs 
    • Sulfonamides 
    • Barbituates 
    • Metformin 

Often no treatment is required – most cases resolve spontaneously with no scarring. 
If the cause is an infection, treating the infection will help (eg acyclovir for herpes) 
Oral antihistamines and topical corticosteroids may help the itch 
In severe disease prednisolone, dapsone or azathioprine may be considered. 

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