In a study done by Elman, 46 patients were treated with blue light (405-420 nm, Clear light™). Of these 46 patients, 80% of them noticed around a 60% improvement of papulonodular acne lesions after eight treatments of 8-15 minutes. These patients had prolonged remission of their acne, which was evident in the eight weeks following the end of their treatment. No side effects were noted in any of the patients [42].
I n another study done by Tzung, they decided to test the efficacy of blue light by treating only one side of the face, and leaving the other side of the face untreated, for comparison. The treated side was selected randomly, and was treated twice weekly for four consecutive weeks. The other half of the face was left untreated as control. Compared with the non-irradiated side, eight sessions of blue light irradiation was found to be effective in acne treatment [43].
In a study by Gold and colleagues, they compared the efficacy between blue light used for 16 minutes biweekly for 4 weeks to 1% clindamycin used twice daily. Blue light therapy was shown to reduce inflammatory acne vulgaris lesions by an average of 34%, as compared to 14% for topical 1% clindamycin solution [44].
I n a study by Tremblay, 45 patients were treated with pure blue light (415 nm and 48 J/cm2), receiving two treatments of 20 minutes per week for a period of 4-8 weeks. They found that the mean improvement score was 3.14 at 4 weeks, and 2.90 at 8 weeks. In fact, nine patients experienced complete clearing at eight weeks. The treatment was well-tolerated, with 50% of patients reporting being highly satisfied with the treatment. This study suggested that blue light is effective in the treatment of acne vulgaris. There were no reported side effects in this study [45].
Kawada and colleagues conducted an open study on acne patients who were treated twice a week up to five weeks with blue light. They found that the acne lesions were reduced by 64%. Two patients experienced dryness, but none of the patients discontinued treatment due to adverse effects [46].
In a study by Omi and colleagues, they investigated the use of blue light on acne. They recruited a total of 28 adult healthy volunteers with facial acne (mean age 28.1 years, range 16-56 years). These patients were treated with a total of 8 serial biweekly 15-min treatment sessions. This study found that overall, there was a 64.7% improvement in acne lesions. They concluded that blue light is a useful treatment for acne [47].
Morton et al. tried to determine the effect of narrow-band blue light in the reduction of inflammatory and noninflammatory lesions in patients with mild to moderate acne. They performed an open study utilizing a blue light source in 30 patients with mild-to-moderate facial acne. Over a 4-week period, patients received eight 10- or 20-minute light treatments, peak wavelength 409-419 nm at 40 mW/cm2. This study concluded that eight 10- or 20-minute treatments over 4 weeks with a narrowband blue light was found to be effective in reducing the number of inflamed lesions in subjects with mild to moderate acne. The onset of the effect was observable at week 5. However, the treatment was found to have little effect on the number of comedones [48].
Although theoretically porphyrins should respond well to blue light, it is a shorter wavelength and therefore does not penetrate well into the skin [49]. Longer wavelengths with Q-bands, such as red light, have been combined with blue light in acne therapy. Red light (wavelength 600-650 nm) penetrates deeper into the skin than blue light. In fact, 635 nm light may penetrate through the skin up to 6 mm, compared with 1-2 mm for light at 400-500 nm. Red light has also been shown to be effective in acne treatment by activating porphyrins in the Q band, and decreases inflammation by controlling cytokine release from macrophages [ 50- 54 ].
Using shorter wavelengths can be more efficient at activation of PplX; however, we have to be concerned that it may not penetrate deeply enough to produce the wanted effects. Photodynamic therapy is described as the use of cytotoxic oxygen-free radicals generated from photoactivated molecular species to achieve a therapeutic response.
5-ALA is a precursor in the heme biosynthesis pathway of protoporphyrin (Pp)-IX. Normally, Pp-IX levels in the tissue are not synthesized high enough to produce major tissue damage [55]. However, exogenous application of 5-ALA can increase the intracellular level of Pp-IX. Hyperplastic cells are believed to uptake Pp-IX more than the normal cells. This is due to hyperproliferating cells needing more Pp-IX for iron to synthesize additional cells and therefore accumulate Pp-IX.
With the knowledge that 5-ALA can increase the intracellular levels of Pp-IX, it is believed that if we apply 5-ALA to the skin, active cells will accumulate this agent and result in accumulation of Pp-IX. This accumulation of Pp-IX can therefore be used as a target for light therapy, which produces reactive singlet oxygen-free radicals that can cause cellular damage. Pp-IX accumulates in the mitochondria and when it is exposed to light, it causes damage to the mitochondria and cause cytochrome C to leak. This stimulates endonuclease activity and plasma and the nuclear membrane loses integrity [56,57].
Topical photodynamic therapy (PDT) has been beneficial for various skin conditions. The FDA approved PDT using a 5-ALA preparation, Levulan (DUSA, USA), for actinic keratoses, and in Europe PDT with methyl ester of 5-ALA (MAL) (Galderma, France) was approved for actinic keratoses and basal cell carcinomas.
However, the problems associated with photodynamic therapy is that it is expensive to perform, it is time consuming, and it is more painful than blue light alone. Patients have reported erythema, stinging, pruritus, pain, and tightening after this intervention [58].