Allergic contact dermatitis to topical prodrugs used in photodynamic therapy

Topical photodynamic therapy (PDT) is a well-established treatment for actinic keratosis, Bowen's disease and superficial basal cell carcinoma and its use has also been explored for a variety of other indications.(1,2,3) Treatment involves application of a pro-drug (either 5-aminolaevulinic acid (ALA) or its methlyester, methylaminolevulinate (MAL)) which is preferentially taken up by dysplastic or neoplastic cells and converted into the active photosensitiser protoporphyrin IX (PPIX). Subsequent activation of PPIX by red light results in the production of cytotoxic oxygen species, inflammation and relatively selective diseased tissue destruction. This article is protected by copyright. All rights reserved.