PDT works via application of a photosensitizing agent immediately prior to light exposure.
At 23MD, we use a highly sophistacated photosensitizer containing 5% aminolevulinic acid (5-ALA). Acne Ellipse Photo Spray encapsulates 5-ALA in a liposome, which aids penetration into the top layer of the skin. Once absorbed, 5-ALA can be activated by specific wavelengths of light, to produce reactive oxygen that kills bacterial overgrowth of P. acnes, the bacteria that causes acne (1, 2, 3). At 23MD, Ellipse Nordyls Laser is used to deliver light at these specified wavelengths.
A 2009 systematic review of laser and light therapies for treatment of acne analyzed data from two trials comparing PDT to placebo. This study showed a significant reduction in inflammatory lesion counts in the PDT group compared with placebo. (4)
The two studies showed a reduction in inflammatory lesions of 27.6%, 7.9%, and 41.9% at 1, 3, and 6 months using ALA with 630 nm light for mild-to-moderate acne.
More recently, in a large self-controlled multicenter trial with 397 patients in China low-dose ALA (5% gel) with one hour incubation and 633 nm LED light resulted in overall clearance rates of 82.1% after three or four treatment sessions. (5) The efficacy of ALA-PDT was noted to increase with corresponding baseline acne severity.