Adverse Effects of Topical Photodynamic Therapy

A Consensus Review and Approach to Management

S.H. Ibbotson; T.H. Wong; C.A. Morton; N.J. Collier; A. Haylett; K.E. McKenna; R. Mallipeddi; H. Moseley; L.E. Rhodes; D.C. Seukeran; K.A. Ward; M.F. Mohd Mustapa; L.S. Exton


The British Journal of Dermatology. 2019;180(4):715-729. 

In This Article

Allergic Contact Dermatitis to Prodrugs

Topical PDT induces an inflammatory reaction consisting of erythema, often with some oedema and subsequent crusting; these are expected effects of topical PDT. The degree and severity often reflect the severity of photodamage and the area that is treated. While it could be the development of an irritant dermatitis, the possibility of the patient becoming sensitized and having developed allergic contact dermatitis to the prodrug should be considered, especially with a prolonged and persistent inflammation following PDT.

There are independent reports of allergic contact dermatitis arising to MAL.[143–149] In one study, positive patch testing to MAL cream (but not to placebo) was seen, indicating that this is likely to be due to the prodrug itself and not the excipient.[147] The risk of sensitization is predicted to be of the order of 1–2%.[146,147] However, it is important to be aware of this possible adverse effect as a more generalized dermatitis can occur if this is not recognized and PDT is continued.[145,150] Contact dermatitis to MAL has been reported and, more recently, to BF-200 ALA.[149]

Reviewing the separate studies, the risk of sensitization is increased in those patients who have had multiple treatments with PDT and large areas treated.[147,149] It is important to be aware of and have a low threshold for considering patch testing in patients who develop a more severe or atypical reaction to PDT. With increasing use of dPDT for large-area treatment it would be wise to be vigilant in this patient group.