Photo-dynamic Therapy uses a natural colorless medicine that makes individual areas of skin very responsive to light. After this painless application and a short wait we then use a special “blue light” illuminator to apply a carefully controlled amount of ordinary visible blue light. This combination has been proven to reduce or eliminate much of the damage caused by sunlight. It also improves many cases of adult acne.
This is well accepted therapy. The major drawback is that you should avoid additional light exposure for 48 hours after the natural photosensitizer is applied in order to avoid a sunburn on the areas where the medicine was applied.
Dermatology 101: Blue Light for Sun Damage