Phototherapy has been an alternative method of treating acne for some time. But does phototherapy really work? Let’s take a good look at how phototherapy actually works by looking at some trials and acne research.
Ultraviolet light is scarcely used. Yet, it is well known that acne often improves clinically after exposure to sunlight or artificially produced solar radiation and more than 70% of patients report definite improvement after exposure to the sun during the summer.
Reddening, as well as ultraviolet light-induced tan,produce a camouflage effect. Its therapeutic action might be linked to a biologic effect of the sunlight on the pilosebaceous system. It may have an anti-inflammatory action in acne, possibly by its effect on follicular Langerhans cells. P. acnes produce porphyrins which absorb light energy at the near ultraviolet and blue light spectrum.
Irradiation of P. acnes colonies in vitro with blue visible light leads to photoexcitation of bacterial porphyrins, singlet oxygen production and eventually bacterial destruction.
As well, they have comedogenic potential because squalene is oxidized to squalene peroxide, which, in turn, may irritate the follicular keratinocytes. The use of visible light alone is perhaps the most practical, common and free treatment existing. However, it is carcinogenic and the photoaging effects render its use unwise.
Blue light is theoretically the most effective visible wavelength for photoactivation of the major endogenous porphyrin component of P. acnes, but has poor depth of skin penetration. The red light is less effective at photoactivating porphyrins, but penetrates more deeply into tissue.
Red light may also have anti-inflammatory properties by influence of cytokines released from macrophages. Light in the violet-blue range (407–420 nm) has been shown to exhibit a phototoxic effect on P. acnes when irradiated in vitro. This effect is most likely due to the destruction of porphyrins necessary in heme biosynthesis.
Researchers have conducted a study to determine if the levels of P. acnes decreased when irradiated in vivo with this phototherapy radiation. This study examined two groups of patients simultaneously irradiated twice a week with a high-intensity fiber optic lamp emitting visible light in the violet-blue range for a total of 4 weeks. Different parts of the face were treated either on the forehead or the cheek for a 20-min session with the lamp placed 5 cm from the skin.
After 6 sessions, both the treated and the untreated symmetric area demonstrated a significant reduction in the levels of P. acnes. They also observed that 7 of 10 patients with mild-to-moderate acne showed significant improvement in reducing the number of non-inflammatory, inflammatory and total facial lesions.
The authors conclude that the use of visible light may inhibit heme production in P. acnes. Some other researchers have conducted a study to evaluate the use of blue light (peak 415 nm) and a mixed blue and red light (peaks at 415 and 660 nm) in the treatment of acne vulgaris.
They examined 107 patients with mild-to-moderate acne vulgaris that were randomized into four treatment groups: blue light, mixed blue and red light, cool white light and 5% benzoyl peroxide cream. Patients in the phototherapy group used portable light sources and irradiation was carried out daily for 15 min.
Assessments were performed every 4 weeks. After 12 weeks of active treatment, a mean improvement of 76% in inflammatory lesions was achieved by the combined blue-red light phototherapy and the result was significantly superior to that obtained with the other treatments.
Regarding comedones treated with the blue-red light combination, a 58% of improvement again indicates better results than those achieved by the other treatments.
Considering all the groups under study, the authors concluded that phototherapy with mixed blue-red light, probably by combining antibacterial and anti-inflammatory action, is an effective means of treating acne vulgaris of mild-to- moderate severity, with no significant short-term adverse effects. Further studies are required to elucidate the exact mechanism of action.
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