These endogenous porphyrins (mainly coproporphyrin III[1]) photosensitize the bacterium and, upon illumination, result in the formation of singlet oxygen, which combines with cell membranes to destroy the P. acnes. This process is dependent on the rate of production of excited porphyrin molecules, which is influenced by the concentration of porphyrins, the concentration of photons, the temperature, and the wavelength of the photons.[2]
Blue light and blue-red combinations have demonstrated efficacy in mild to moderate inflammatory acne, having a physical modality comparable to treatment with topical clindamycin but inferior to benzoyl peroxide plus clindamycin.[3] The viability of 24-hour in vitro P. acnes cultures was reduced by four and five orders of magnitude after two and three illuminations, respectively, with intense blue light (407-420 nm).[4] In a randomized controlled trial evaluating the use of blue light (peak at 415 nm) and mixed blue and red light (peaks at 415 and 660 nm, respectively) in the treatment of mild to moderate acne vulgaris, a mean improvement of 76% in inflammatory lesions was achieved by the combination blue-red light phototherapy after 12 weeks of daily treatment. This result was statistically superior to that achieved by blue light at Weeks 4 and 8 ( p =0.02); benzoyl peroxide at Weeks 8 ( p =0.02) and 12 ( p =0.006); and white light at all assessments ( p <0.001)[5] ...
Wound Healing/Antiaging
The wound-healing process has been used in the rejuvenative model. This process consists of overlapping phases of inflammation, proliferation, and remodeling. During inflammation, neutrophils, leukocytes, monocytes, and/or macrophages migrate to the site of the wound; monocytes differentiate into phagocytic cells to phagocytose debris and secrete growth factors. Complement system proteins are activated, stimulating mast cell degranulation and attracting more neutrophils. Macrophages release platelet-derived growth factor, which stimulates the chemotaxis and proliferation of fibroblasts. Leukocytes and macrophages also secrete fibroblast growth factor, which promotes the recruitment and growth of more fibroblasts, establishing the proliferative phase of the wound-healing process.[6,7] Leukocyte numbers decrease, and macrophages begin to diminish slowly as fibroblast levels peak days later. The remodeling phase begins with a fall in the number of fibroblasts; active fibroblasts either differentiate into myofibroblasts or dedifferentiate into dormant fibrocytes. The fibroblast plays a key role in the dermis during the second and third phases: it not only synthesizes collagen and elastin but also regulates the homeostasis of the ground substance in addition to maintaining the collagen fibers. Myofibroblasts position themselves along collagen fibers and exert a longitudinal force that tightens and aligns the latter. Remodeling may take 3-6 months or longer. The end result is the deposition of new collagen fibers in a better organized cellular matrix accompanied by elastogenesis and angiogenesis. A layer of new, tightly-organized collagen runs below and is attached to the basement membrane of the dermoepidermal junction.
Red light (633 nm) may aid in effectively healing long-term torpid ulcers and may enhance angiogenesis in the rabbit ear chamber model.[8] Six hundred thirty-three nm light significantly stimulates a faster and better linearly-oriented monolayer formation of fibroblasts in vitro as compared with controls. It accelerates mast cell degranulation and increases the synthesis of fibroblast growth factor from photoactivated macrophage-like cells.[9,10] Irradiation with low-level narrowband 660 nm red light induced the release of growth factors from macrophages in vitro and significantly improved postoperative wounds in vivo.[11,12]
Red light, in the absence of a wound, may be beneficial as an antiaging therapy. Mast cells are always present in the dermis; 633 nm red light may have the same effect on them regardless of their involvement in the inflammatory process. The surrounding tissue recognizes this degranulation as inflammation, and so the wound healing process is jump-started. Visible yellow light (588 nm) may also be beneficial as antiaging therapy through mechanisms similar to the action of red light (see Gentlewaves, Light BioScience, LLC, Virgina Beach, VA).
-- William Abramovits, MD; Peter Arrazola, BA; Aditya K. Gupta, MD, PhD, FRCP(C)
SKINmed. 2005; 4 (1): 38-41. ©2005 Le Jacq Communications, Inc.

Effects of phototherapy on pressure ulcer healing in elderly patients after a falling trauma: A prospective, randomized, controlled study
Background:
The effects of infrared and red pulsed monochromatic light, with varied pulsations and wavelengths, on the healing of pressure ulcers were evaluated in this prospective, randomized, controlled study.
Methods:
Elderly patients ( 65 years) with Stage 2 or 3 skin ulcers were enrolled and assigned to one of two groups. Both groups were given the same standard ulcer therapy. One group was also given phototherapy with pulsed monochromatic infrared (956 nm) and red (637 nm) light. Treatments lasted 9 min each time using a regimen with pulse repetition frequency varied between 15.6 Hz and 8.58 kHz. Patients were followed for 10 weeks or until the ulcer was healed, whichever occurred first. The ulcer surface area was traced weekly.
Results:
Patients treated with pulsed monochromatic light had a 49% higher ulcer healing rate, and a shorter time to 50% and to 90% ulcer closure compared with controls. Their mean ulcer area was reduced to 10% after 5 weeks compared with 9 weeks for the controls.
Conclusion:
The results are encouraging as pulsed monochromatic light increased healing rate and shortened healing time. This will positively affect the quality of life in elderly patients with pressure ulcer.
-- V. Schubert, Photodermatology Photoimmunology & Photomedicine, Volume 17, Number 1, February 2001, pp. 32-38(7)
Publisher:Blackwell Publishing

Low Level LASER Therapy
Physiological effects
Many papers suggest low-level laser therapy (LLLT) may be of use in a wide variety of conditions, due to the physiological effects it exerts on soft tissue (Karu, 1988; Dyson, 1990; Young et al., 1989). LLLT is non-thermal as it does not produce heat in the target tissue. Instead, it triggers a photochemical response, triggering normal cell function. The photon emission with red or infra-red light is absorbed by photoreceptors in the tissue. Changes in the cell membrane alter its permeability, increase ATP synthesis and other metabolic activities, and therefore promote a range of physiological changes. Different wavelengths appear to be absorbed by different receptors (Young et al., 1989). Most authors agree that enhanced wound healing is due to the increased proliferation of cells (Baxter, 1994). The photochemical changes stimulated by the action of light on either the cell membrane or the nucleus of the cell are listed in Table 1.
This type of therapy is, therefore, of use in stimulating healing in soft tissues, to resolve inflammation, give pain relief, improve the tensile strength of the wound, increase the speed at which it heals and stimulate the immune system to resolve infection. Rochkind et al. (1989) also found that the effect of irradiating one area was gleaned elsewhere on other wounds of the body, suggesting the systemic effects of LLLT.

Table 1: Physiological changes as a result of laser light on soft tissue

• increased local vasodilation
• angiogenesis
• fibroblast production
• collagen synthesis
• mast cell population and degranulation
• T and B lymphocyte production
• the release of local endorphins
• changes in local prostaglandins
(Karu, 1988; Dyson, 1990; Baxter, 1994)

-- Yvonne Franks, Journal of Community Nursing. (April/1999) Volume 13, Issue 04