ABSTRACT
Aminolevulinic acid is a topically administered metabolic precursor of protoporphyrin IX. When the proper wavelength of light activates protoporphyrin IX, singlet oxygen is produced, resulting in a local cytotoxic effect. Aminolevulinic acid is indicated for use in photodynamic therapy to treat actinic keratoses and superficial basal cell carcinomas. A 54-year-old woman was treated for the first time with photodynamic therapy using 20% aminolevulinic acid (ALA) gel for Bowen’s disease of the vulva. Patch testing showed positive reactions to the photosensitizing gel ‘as is’ and to a 20% aqueous solution of ALA, but negative reactions to the other ingredients. Ten controls were negative to 20% ALA in water. The patient had previously become sensitized to ALA was unknown. While driving to work on a sunny morning, a 30-year-old dermatology resident experienced intense burning on his forehead that abated abruptly upon arrival at clinic.
