30th July 2026

Aetiology

FDE is a delayed type IV hypersensitivity reaction with CD8 T cell mediation at the dermo-epidermal layer, causing keratinocyte and melanocyte damage. CD8 T-cells remain quiescent but primed in the resolved lesion until the offending agent is reintroduced.

Drugs most commonly associated with FDE include: 

• Antibacterial agents: trimethoprim – sulfamethoxazole, tetracyclines, penicillin, quinolones, dapsone)
• NSAIDS
• Paracetamol
• Barbiturates
• Antimalarials
• Carbamazepine

FDE can uncommonly occur with food and food additives. There are also some reports of patients developing FDE secondary to COVID-19 vaccinations.