Discuss light and laser therapy of acne vulgaris.

One of the important pathogenic mechanisms of acne is Propionibacterium acnes growth in the follicle. P. acnes produces porphyrins, which can be activated by visible light, inducing a photodynamic reaction that kills the bacteria. Several studies have shown improvement in acne utilizing visible light, especially in the blue light spectrum (400 to 420 nm) where these porphyrins are most strongly activated. Blue and red (660 nm) light combined has also been used, as well as light in the yellow and green spectrum (500 to 600 nm). Several studies have shown improvement in acne lesions with relatively few side effects. However, clearing seems to be variable among patients and relapse rates are high.

Photodynamic therapy utilizes a lower-power visible light source in which the effectiveness is amplified by the use of a topical photosensitizing agent, most often aminolevulinic acid (ALA). Photodynamic therapy tends to have more side effects, such as burning at the sites of treatment and postinflammatory hyperpigmentation. Existing studies suggest promise for this therapy, with sustained improvement in acne for up to 20 weeks after several treatments. Several laser devices have been employed and studied in the treatment of acne. There are a few small studies evaluating the 1450-nm diode laser was used to target and destroy sebaceous glands. Due to differences in treatment regimen and other allowed acne treatment, no comparisons can be made between studies.

Elman M, Lebzelter J: Light therapy in the treatment of acne vulgaris, Dermatol Surg 30:139–146, 2004.

Theboutot D, Gollnick, H, Bettoli V, et al: New insights into the management of acne: an update from the Global Alliance to Improve Outcomes in Acne Group, J Am Acad Dermatol 60:S1–S50, 2009.