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Acne therapy is and has always been an important part of every dermatology practice. Whether we are accustomed to treating infantile acne, teenage acne, adult acne or even the Aesthetic complications of acne, therapy for acne is a complicated issue.
Younger patients and their parents are now more involved in decision-making regarding treatments. In addition, with the new isotretinoin regulations making prescribing of the drug more difficult, new therapies are needed for acne. Laser or light therapy for acne could be an option in many of these cases.
Many lasers and light devices have been used to treat acne, including the pulsed dye laser, infrared, nonablative lasers, light-emitting diodes, KTP, 1,320 nm Nd:YAG, 1,450 nm diode, radiofrequency and intense pulsed light (IPL). Below we will discuss the most commonly used devices and those with the most data supporting their use.
The pulsed dye laser (PDL) was the first laser reported to be effective for acne (Seaton et al. Lancet. 2003). In this initial double-blind, controlled study, patients treated with the PDL (low fluence) showed a reduction in lesion count of 53 percent (49 percent being inflammatory lesions).
With its deep penetration and nonablative heat-delivering actions, the 1,450 nm mid-infrared diode laser has been reported to improve inflammatory acne. This laser also has been used as a treatment for atrophic facial scarring and photorejuvenation, with modest results.
The 1,450 nm diode laser uses deep heating to alter the sebaceous glands in the dermis, while using cryogen to cool the epidermis and thereby protect it from damage.
Sebum excretion rates do not change dramatically after treatment with the 1,450 nm diode laser, so the exact mechanism of action is still unknown (Laubach et al. Lasers Surg Med. Feb 2009). In one clinical pilot study, inflammatory lesion counts in 19 patients decreased by 83 percent after three treatments with the laser (Friedman et al. Dermatol Surg. 2004).
This "color-blind" wavelength can be used on all skin types, yet, as with any cryogen-assisted device, risk of postinflammatory hyperpigmentation in darker skin types exists. Additionally, this laser therapy is very painful and is time-consuming to perform.
Of all the light devices to date, photodynamic therapy (PDT) as a treatment for acne has been the most researched. PDT works in several manners.
Propionibacterium acnes produces its own porphyrins, which, when exposed to visible light, produce free radicals that kill the bacteria. Reduction in inflammatory lesions is seen with red and/or blue light alone, but the addition of another prodrug photosensitizer (ALA or MAL) results in added benefit.
Blue light is the best activator of porphyrins, but due to the short wavelength, this light does not penetrate deeply.
Typically, longer wavelengths are the ones capable of reaching the sebaceous glands, including both red and infrared light (IPL). Coherent light, such as is found in lasers, also has better penetration than noncoherent light (LED).
Bacterial destruction is the proposed mechanism of action of PDT, though in reality, the exact mechanism of action may still be unknown.
One recent study indicated that even nonviable "laser/heat-killed" P. acnes was able to induce the inflammatory cascade, indicating that physicians may need synergistic therapies when using light devices (Lyte et al. Exp Dermatol. July 2009).
MAL-PDT or ALA-PDT decreases the lesion count by an average of 59 percent to 69 percent after 12 weeks. ALA and MAL seem equally effective in the treatment for acne (Haedersdal et al. J Eur Acad Dermatol. 2008).
Improvements with PDT are temporary, as with most acne treatments, and typically last approximately six months after the discontinuation of therapy.