Photodynamic light therapies (PDLs) have emerged as significant adjuvant approaches for treating acne. In particular, such therapies have been used for acne refractory to standard retinoid or combined retinoid and antimicrobial regimens. Why write about PDL in a column devoted to topical cosmeceutical products and ingredients? Blue light warrants inclusion because it has been studied in comparison to topical cosmeceutical treatments, and it is used in conjunction with other topical approaches.
Blue light exerts a phototoxic effect on the heme metabolism of Propionibacterium acnes, and it is considered effective by targeting part of the etiologic pathway of acne. It has become a widely used option for inflammatory acne (J. Drugs. Dermatol. 2006;5:605-10).
In 1990, Meffert et al. were the first to show that a blue light–type, high-pressure lamp could improve acne and seborrhea (10 10-minute treatments, cumulative light dose 325 J/cm2). Given the copious amounts of porphyrins stored in lipophilic P. acnes, the technology could be targeted to destroy propionibacteria, and the researchers observed a decline in the porphyrin content inside acne follicles. They concluded that short-range visible light (400-420 nm) was a viable option for acne treatment during the light-poor season of the year (Dermatol. Monatsschr. 1990;176:597-603). It was subsequently established that treatment with UV-free blue light in the range of 405-420 nm leads to the elimination of acne bacteria by virtue of the effects on the porphyrins generated naturally by P. acnes (J. Cosmet. Laser. Ther. 2003;5:111-7). Notably, blue light appears to photoinactivate P. acnes, but it does not penetrate deeply into the skin (Dermatol. Online J. 2011;17:2).
In an open study of the then-novel high-intensity, enhanced, narrow-band, blue-light phototherapy, Kawada et al. treated 30 acne patients (27 female, 3 male) twice a week for up to 5 weeks. A reduction of 64% was seen in acne lesions, and in vitro data showed a significant decline in P. acnes, but not in Staphylococcus epidermidis (J. Dermatol. Sci. 2002;30:129-35).
Mechanism of action
In 2006, Shnitkind et al. studied the effect of narrow-band blue light on the inflammatory process in the presence and absence of cytokines and ultraviolet B using interleukin-1 alpha (IL-1alpha) and intercellular adhesion molecule 1 (ICAM-1) as markers for inflammation. They found that blue light treatment of HaCaT and hTERT cells decreased levels of IL-1alpha by 82% in HaCaT and by 75% in hTERT. When blue light was combined with ultraviolet B, the respective reductions were 95% and 91%. Similar reductions in ICAM-1 expression were seen in HaCaT, but not in hTERT. The researchers concluded that narrow-band blue light exerts anti-inflammatory effects on keratinocytes by reducing cytokine-induced synthesis of IL-1alpha and ICAM-1. They suggested that these findings imply a broader range of effects is exerted on the inflammatory process by narrow-band blue light than previously understood (J. Drugs. Dermatol. 2006;5:605-10).
In 2000, Papageorgiou et al. randomized 107 patients with mild to moderate acne to four treatment groups: blue light (peak at 415 nm), mixed blue and red light (peaks at 415 and 660 nm), cool white light, and 5% benzoyl peroxide cream, for 12 weeks of active treatment. Phototherapy using portable light sources was conducted daily for 15 minutes; comparative assessments among the three phototherapy groups were done with observers blinded. The investigators found that the greatest improvement in acne lesions occurred in the blue and red light combined group. The blue/red treatment was significantly superior to blue light alone at 4 and 8 weeks but not 12 weeks, benzoyl peroxide at weeks 8 and 12, and white light at all assessments (Br. J. Dermatol. 2000;142:973-8).
Gold et al. performed a multicenter clinical evaluation comparing blue light to topical 1% clindamycin solution with respect to safety and efficacy. They found that clindamycin was associated with a 14% reduction of inflammatory lesions, but blue light reduced such lesions by an average of 34% (J. Drugs. Dermatol. 2005;4:64-70).
In another study, 20 patients with moderate to severe facial acne were treated in four weekly sessions with topical aminolevulinic acid (ALA)-photodynamic therapy with blue light (415 nm) on the right side of the face, or blue light alone on the left side of the face. At 4, 8, 12, and 16 weeks after the start of treatment, the mean percent reductions in inflamed lesions were higher in the ALA-PDT areas (32%, 50.9%, 65.9%, and 71.1%, respectively) than in the blue light–only treatment areas (20.7%, 27%, 57.7%, and 56.7%), but the differences were not statistically significant. Side effects, which included pain, stinging, erythema, itching, peeling, oozing, and pustules, were more pronounced in the areas treated with ALA-PDT (Photodermatol. Photoimmunol. Photomed. 2007;23:186-90).