| DERMATOLOGY | PEER-REVIEW of the population1


experience variable degrees of acne at some point during their lives. Acne may occasionally be resistant to conventional medical-cosmetic treatments2–4


A . . Besides


conventional medical treatments, chemical peels and different energy sources, either alone or in sequential combinations, have been proposed with variable degrees of success. Energy sources, such as lasers (585–595 nm pulse dye laser, 800 nm diode, 532 nm KTP, and 1064 nm Nd:YAG), 515–950 nm intense pulsed polychromatic light (IPPL), 415 nm and 633 nm light emitting diodes (LED), as well as photodynamic therapy (PDT) with or without topical photosensitizers have been proposed. Light-based acne treatments usually achieve three main goals: reduction of intra-follicular concentrations of P. acnes, a decrease of biological sebaceous gland activity, and the decongestion of skin pores5–7


There is a need for


new, safe, and effective alternative


treatment


strategies for patients affected by moderate-to-severe acne, who cannot or do not want to take oral medications, mainly isotretinoin. This particular group of patients is slowly increasing in number and may include women who are or want to become pregnant; individuals intolerant or allergic to acne-specific oral medications; and those affected by congenital or acquired pathological conditions, such as congenital or familial hyperlipidaemia and liver diseases. Conventional single-wavelength single-


exposure (SW-SE) acne-PDT seems to negatively interfere with the biological activity of sebaceous glands despite the constant bio-stimulation of pilo- sebaceous units provided predominantly by androgens, which are the strongest


CNE VULGARIS IS THE most common skin alteration


adolescents and young adults,


driving force behind this skin condition4 among affecting


approximately 80–95% . Both genders


.


More specifically, the photo-chemical reaction triggered by SW-SE acne-PDT can be used to selectively destroy intra- follicular P. acnes as well as photo- modulate sebaceous activity within affected anatomical areas. It is universally accepted that three fundamental elements are needed to start and maintain an effective PDT reaction:  Specific photosensitizers in suitable concentrations and selective micro-anatomical distributions


 Light wavelengths to be selectively absorbed by specific photosensitizers


 Sufficient concentrations of molecular oxygen within irradiated tissues throughout the full PDT process.


To produce the best clinical effects, specific photosensitizers should be allowed to concentrate within affected target tissue, located within reach of selective


light


To produce the best clinical


effects, specific photosensitizers should be allowed to concentrate within


affected target tissue, located within reach of selective light wavelengths.


wavelengths. Presently, there is no


universally accepted agreement on pro-drug concentrations, occlusive contact time (OCT), light wavelengths, and exposure


times.


Nevertheless, acne-PDT continues to produce significant clinical results irrespective of a standardization of treatment protocols. The


authors are convinced that relatively short OCT (1–2 hours) may provide suitable concentrations of active porphyrins within selected tissue and that intra- cellular pro-drug conversion continues after a single irradiation of porphyrin- specific wavelengths. The choice of wavelength is not an easy decision to make since blue light (414–440 nm), even if better absorbed by MAL/5-ALA-derived PpIX, does not penetrate deep into the skin; while red light (633–690 nm), does penetrate deeper into skin layers but is not as well absorbed as blue light. For these reasons the authors decided to introduce a new treatment protocol based on three sequential irradiations starting with blue light as a superficial, efficient photo- bleacher, opening the way for two


prime-journal.com | August/September 2015  23


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