When sun damages the skin it damages the entire are that has been exposed. As time passes precancerous lesions know as actinic keratosis develop within these areas. Surgery or freezing with liquid nitrogen can treat individual lesion, similar to a gardener pulling weeds in a garden. If there is more widespread damage then photodynamic therapy is used to treat the entire area of sun damaged skin, similar to weed killer being applied to a garden.

The objective of treatment is to treat visible pre-cancers, to reduce the subsequent risk of skin cancer development and to improve the appearance and function of the skin.

This is a light activated chemotherapy. The photosensitizing drug is applied to the treatments site where it is preferentially absorbed by sun damaged or precancerous cells. The cream is then removed and the skin is exposed to a red LED light that activates the drugs and kills the abnormal cells

PDT has many advantages over alternate treatments. The treatment is carried out in the office and is safe and well tolerated and only mildly uncomfortable. It treats individual lesions and back round sun damage. It reduces the subsequent risk of developing skin cancer in the treated area and also results in an improved appearance to the skin. Following treatment the skin is very light sensitive for 48 hours: patients need to stay indoors. Patients usually get a sun burn like reaction that can be mild, moderate or severe. Even severe cases resolve completely but these cases sometimes need to take antibiotics and antiviral medication.