. What is it?
Photodynamic therapy is a treatment involving the application of aminolevulinic acid (ALA) to the skin followed by exposure to a red or blue light. It is most commonly prescribed for precancerous lesions known as actinic keratosis.
How is it done?
The skin is cleaned with alcohol or acetone and then the ALA is applied to the affected area. This application is followed by a period of incubation and could be from 15-90 minutes depending on the treatment regimen for your condition. After the incubation the skin is exposed to the red or blue light for between 16 and 60 minutes.
What to expect?
The most common reaction is a warm, sometimes mildly uncomfortable, sensation during exposure to the light. Over the next week some patients experience peeling, crusting, and redness.
Importantly, patients will be sensitive to the sun and bright fluorescent light for up to 48 hours after the treatment. It is important to stay indoors and wear a broad hat after the treatment. Sometimes patients who are exposed to direct sun in the 48 hours after treatment (even with sunscreen) experience uncomfortable crusting and blistering.
How effective is it?
Most trials show 80-90% of actinic keratosis resolve after treatment. Sometimes a series of treatments are needed to achieve desired results.