Photodynamic therapy (PDT) is mainly used in the treatment of actinic keratoses (pre-cancerous lesions) but also for basal cell and superficial squamous cell carcinomas (in situ).

PDT uses photosensitizing agents to destroy pre-cancerous or cancerous cells.

First, the photosensitizing drug dispensed as a cream is applied to the area to be treated for 3 hours (methyl aminolevulinate (Metvix)). The cells absorb the photosensitizing drug.

After some time, the area to be treated is exposed to low intensity red light or outdoor daylight. The photosensitizer in cancer cells absorbs light, causing a chemical reaction that destroys the cancer cells (normal cells are usually not affected).

The main side effects reported are of short duration and self-limited. They include sensitivity to light for the first few days after treatment, localized redness and burning pain at the treatment site, and swelling and itching.