In 2007, Lee et al. set out to examine the efficacy of combining blue and red LED phototherapy for acne in a study of 24 patients with mild to moderately severe facial acne. Twice weekly for 4 weeks, patients were treated with quasi-monochromatic LED devices, alternating blue (415 nm) and red (633 nm) light. Fourteen patients self-reported improvements in skin tone and texture. Improvements in noninflammatory and inflammatory lesions were substantial (34.28% and 77.93%, respectively). The researchers concluded that combined blue and red LED phototherapy is a safe and effective option, especially for papulopustular acne (Lasers Surg. Med. 2007;39:180-8).
In 2009, Sadick evaluated the efficacy of the combination of blue (415 nm) and near-infrared (830 nm) LED therapy for moderate acne in 13 females and 4 males ranging in skin type from II to VI and in Burton acne grade at baseline from 1 to 5. Twice-weekly 20-minute sessions were conducted for 4 weeks, alternating between blue and near-infrared light. Eleven patients exhibited improvement ranging from 0% to 83.3%, and 6 patients discontinued the study. A decreasing trend was observed in the Burton grade. Noninflammatory lesion counts improved in seven patients but increased in four. Sadick noted that these results paled in comparison to the effectiveness of the blue and red combination at lowering inflammatory lesions seen previously, but encouraged the study of the combination phototherapy in a much larger population (J. Cosmet. Laser Ther. 2009;11:125-8).
Several recent reviews have found that red light–activated MAL-PDT, the combination of blue and red light, and aminolevulinic acid as a photosensitizing agent before treatment with blue light, red light, or the 595-nm pulsed dye laser are among the most promising evidence-based laser- and light-based therapies for acne (Semin. Cutan. Med. Surg. 2008;27:207-11; J. Eur. Acad. Dermatol. Venereol. 2008;22:267-78; Dermatol. Surg. 2007;33:1005-26).
In a systematic literature review of randomized controlled trials of light and laser therapies for acne vulgaris (using the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, CINAHL, PsycINFO, LILACS, ISI Science Citation Index, and Dissertation Abstracts International), Hamilton et al. found that trials of blue light, blue-red light, and infrared radiation were more successful, especially when multiple treatments were used. Notably, blue-red light demonstrated better short-term effectiveness than did topical 5% benzoyl peroxide cream (Br. J. Dermatol. 2009;160:1273-85).
Kim and Armstrong have noted that blue light has been demonstrated to photoinactivate P. acnes, but it does not penetrate deeply into the skin. It is believed to work synergistically, however, with red light, which is less effective than blue light at exciting porphyrins but can reach deeper sebaceous glands and may impart an anti-inflammatory effect by inciting cytokine release from macrophages (Dermatol. Surg. 2007;33:1005-26). Indeed, Kim and Armstrong found that combined blue-red light therapy was more effective at lowering the number of inflammatory acne lesions than were benzoyl peroxide monotherapy and blue light monotherapy (Lasers Surg. Med. 1989;9:497-505).
Conclusions
A lengthy review of the literature and personal experience treating patients have convinced me that blue light is an effective treatment for acne. P. acnes is most susceptible to the blue light wavelengths of 407-420 nm. Addition of red light may help speed resolution of inflammatory lesions through an anti-inflammatory effect. Blue and red light devices are efficacious when used in the office if the devices deliver enough joules.
Many at-home devices and iPhone apps have hit the market. These are a great alternative to irritating topicals and antibiotics, and they may help increase compliance. However, many at-home light devices are too weak (do not emit enough joules), or emit a broad range of light (rather than 407-420 nm). The manufacturers of some of these products claim that the heat produced by the devices improves acne, but there is a paucity of research proving this point. In my opinion, using an at-home device twice a day that delivers 407-420 nm (with or without the addition of red light), and delivers enough joules (at least 25 J/cm2), is an effective method of treating acne. For comparison purposes, the in-office Omnilux delivers around 49 J/cm2 but is used only two or three times per week. Know your wavelengths and joules when trying to decide which device to sell in your practice or recommend to patients.