30th July 2026

Investigations

Diagnosis is clinical, based upon the history and examination, but if there is diagnostic uncertainty, the following investigations may be considered:

• Skin biopsy: necrotic keratinocytes in the epidermis, lympho-eisinophilic cells in the dermis with dermal oedema 
• Oral provocation test: low dose of the offending agent is administered. It is contraindicated with patients with generalised bullous fixed drug eruption. 
• Patch testing: application of the offending agent to area of recurring lesion to elicit a reaction.