Photobiostimulation is a well-researched phenomenon.

Since the original Mester paper first published in 1967, titled “The effect of laser beams on the growth of hair in mice” [PubMed ID: 5732466], a large body of research has been published to report on the medical applications of light-tissue interactions. Recent studies of Low-Level Laser Therapy have examined the mechanisms and effects of such therapeutic energy on hair growth, wound healing, tissue in-vitro, acne, and skin rejuvenation.

Medical Literature 

“Hair Regrowth and Increased Hair Tensile Strength Using the HairMax LaserComb for Low-Level Laser Therapy”

Satino, JL, Markou, M.
International Journal of Cosmetic Surgery and Aesthetic Dermatology.2003. Volume 5, Number 2.
Request a copy of this paper.

The authors wished to confirm the efficacy of low level laser therapy (LLLT) using a Hair-Max LaserComb for the stimulation of hair growth and also to determine what effect LLLT with this device had on the tensile strength of hair. Thirty-five patients, 28 males and 7 females, with androgenetic alopecia (AGA) underwent treatment for a six-month period. Both the hair counts and tensile strength of the hair were affected very beneficially in both sexes in the temporal and vertex regions, with the males and vertex areas showing the most improvement.

“HairMax LaserComb(R) Laser Phototherapy Device in the Treatment of Male Androgenetic Alopecia: A Randomized, Double-Blind, Sham Device-Controlled, Multicentre Trial.”

Leavitt M, Charles G, Heyman E, Michaels D.
Private Dermatology Practice, Maitland, Florida, USA.
Clin Drug Investig. 2009;29(5):283-92. doi: 10.2165/00044011-200929050-00001.
PubMed ID: 19366270

The use of low levels of visible or near infrared light for reducing pain, inflammation and oedema, promoting healing of wounds, deeper tissue and nerves, and preventing tissue damage has been known for almost 40 years since the invention of lasers. The HairMax LaserComb(R) is a hand-held Class 3R lower level laser therapy device that contains a single laser module that emulates 9 beams at a wavelength of 655 nm (+/-5%). The device uses a technique of parting the user's hair by combs that are attached to the device. This improves delivery of distributed laser light to the scalp. The combs are designed so that each of the teeth on the combs aligns with a laser beam. By aligning the teeth with the laser beams, the hair can be parted and the laser energy delivered to the scalp of the user without obstruction by the individual hairs on the scalp.

The primary aim of the study was to assess the safety and effectiveness of the HairMax LaserComb(R) laser phototherapy device in the promotion of hair growth and in the cessation of hair loss in males diagnosed with androgenetic alopecia (AGA). This double-blind, sham device-controlled, multicentre, 26-week trial randomized male patients with Norwood-Hamilton classes IIa-V AGA to treatment with the HairMax LaserComb(R) or the sham device (2 : 1). The sham device used in the study was identical to the active device except that the laser light was replaced by a non-active incandescent light source. Of the 110 patients who completed the study, subjects in the HairMax LaserComb(R) treatment group exhibited a significantly greater increase in mean terminal hair density than subjects in the sham device group (p < 0.0001). Consistent with this evidence for primary effectiveness, significant improvements in overall hair regrowth were demonstrated in terms of patients' subjective assessment (p < 0.015) at 26 weeks over baseline. The HairMax LaserComb(R) was well tolerated with no serious adverse events reported and no statistical difference in adverse effects between the study groups. The results of this study suggest that the HairMax LaserComb(R) is an effective, well tolerated and safe laser phototherapy device for the treatment of AGA in males.

“Cellular chromophores and signaling in LLLT”

M. R. Hamblin, Massachusetts General Hospital

The use of low levels of visible or near infrared light for reducing pain, inflammation and edema, promoting healing of wounds, deeper tissues and nerves, and preventing tissue damage by reducing cellular apoptosis has been known for almost forty years since the invention of lasers. Originally thought to be a peculiar property of laser light (soft or cold lasers), the subject has now broadened to include photobiomodulation and photobiostimulation using non-coherent light. Despite many reports of positive findings from experiments conducted in vitro, in animal models and in randomized controlled clinical trials, LLLT remains controversial. This likely is due to two main reasons; firstly the biochemical mechanisms underlying the positive effects are incompletely understood, and secondly the complexity of rationally choosing amongst a large number of illumination parameters such as wavelength, fluence, power density, pulse structure and treatment timing has led to the publication of a number of negative studies as well as many positive ones.

This introductory review will cover some of the proposed cellular chromophores responsible for the effect of visible light on mammalian cells, including cytochrome c oxidase (with absorption peaks in the near infrared) and photoactive porphyrins. Mitochondria are thought to be a likely site for the initial effects of light, leading to increased ATP production, modulation of reactive oxygen species and induction of transcription factors. In particular signaling cascades are initiated via cyclic adenosine monophosphate (cAMP) and nuclear factor kappa B (NF-kB). These signal transduction pathways in turn lead to increased cell proliferation and migration (particularly by fibroblasts), modulation in levels of cytokines, growth factors and inflammatory mediators, and increases in anti-apoptotic proteins.

The results of these biochemical and cellular changes in animals and patients include such benefits as increased healing in chronic wounds, improvements in sports injuries and carpal tunnel syndrome, pain reduction in arthritis and neuropathies, and amelioration of damage after heart attacks, stroke, nerve injury and retinal toxicity.

"Therapeutic photobiomodulation for methanol-induced retinal toxicity"

Proc Natl Acad Sci U S A. 2003 Mar18; 100(6): 3439-44.
PubMed ID: PMC152311

Methanol intoxication produces toxic injury to the retina and optic nerve, resulting in blindness. The toxic metabolite in methanol intoxication is formic acid, a mitochondrial toxin known to inhibit the essential mitochondrial enzyme, cytochrome oxidase. Photobiomodulation by red to near-IR radiation has been demonstrated to enhance mitochondrial activity and promote cell survival in vitro by stimulation of cytochrome oxidase activity. The present studies were undertaken to test the hypothesis that exposure to monochromatic red radiation from light-emitting diode (LED) arrays would protect the retina against the toxic actions of methanol-derived formic acid in a rodent model of methanol toxicity. Using the electroretinogram as a sensitive indicator of retinal function, we demonstrated that three brief (2 min, 24 s) 670-nm LED treatments (4 J/cm2), delivered at 5, 25, and 50 h of methanol intoxication, attenuated the retinotoxic effects of methanol-derived formate. Our studies document a significant recovery of rod- and cone-mediated function in LED-treated, methanol-intoxicated rats. We further show that LED treatment protected the retina from the histopathologic changes induced by methanol-derived formate. These findings provide a link between the actions of monochromatic red to near-IR light on mitochondrial oxidative metabolism in vitro and retinoprotection in vivo. They also suggest that photobiomodulation may enhance recovery from retinal injury and other ocular diseases in which mitochondrial dysfunction is postulated to play a role.

“Effect of NASA light-emitting diode irradiation on wound healing.”

Whelan HT, Smits RL Jr, Buchman EV, Whelan NT, Turner SG, Margolis DA, Cevenini V, Stinson H, Ignatius R, Martin T, Cwiklinski J, Philippi AF, Graf WR, Hodgson B, Gould L, Kane M, Chen G, Caviness J.
Department of Neurology, Medical College of Wisconsin, Milwaukee 53226, USA.
J Clin Laser Med Surg. 2001 Dec;19(6):305-14.
PubMed ID: 11776448

OBJECTIVE: The purpose of this study was to assess the effects of hyperbaric oxygen (HBO) and near-infrared light therapy on wound healing. BACKGROUND DATA: Light-emitting diodes (LED), originally developed for NASA plant growth experiments in space show promise for delivering light deep into tissues of the body to promote wound healing and human tissue growth. In this paper, we review and present our new data of LED treatment on cells grown in culture, on ischemic and diabetic wounds in rat models, and on acute and chronic wounds in humans. MATERIALS AND METHODS: In vitro and in vivo (animal and human) studies utilized a variety of LED wavelength, power intensity, and energy density parameters to begin to identify conditions for each biological tissue that are optimal for biostimulation. RESULTS: LED produced in vitro increases of cell growth of 140-200% in mouse-derived fibroblasts, rat-derived osteoblasts, and rat-derived skeletal muscle cells, and increases in growth of 155-171% of normal human epithelial cells. Wound size decreased up to 36% in conjunction with HBO in ischemic rat models. LED produced improvement of greater than 40% in musculoskeletal training injuries in Navy SEAL team members, and decreased wound healing time in crew members aboard a U.S. Naval submarine. LED produced a 47% reduction in pain of children suffering from oral mucositis. CONCLUSION: We believe that the use of NASA LED for light therapy alone, and in conjunction with hyperbaric oxygen, will greatly enhance the natural wound healing process, and more quickly return the patient to a preinjury/illness level of activity. This work is supported and managed through the NASA Marshall Space Flight Center-SBIR Program.

“Low level laser therapy (LLLT) as an effective therapeutic modality for delayed wound healing.”

Hawkins D, Houreld N, Abrahamse H.
Faculty of Health, University of Johannesburg, South Africa.
Ann N Y Acad Sci. 2005 Nov;1056:486-93.
PubMed ID: 16387711

Low level laser therapy (LLLT) is a form of phototherapy that involves the application of low power monochromatic and coherent light to injuries and lesions. It has been used successfully to induce wound healing in nonhealing defects. Other wounds treated with lasers include burns, amputation injuries, skin grafts, infected wounds, and trapping injuries. The unique properties of lasers create an enormous potential for specific therapy of skin diseases. As with any new device, the most efficacious and appropriate use requires an understanding of the mechanisms of light interaction with tissue as well as the properties of the laser itself.

“Phototherapy in anti-aging and its photobiologic basics: a new approach to skin rejuvenation.”

Trelles MA.
Instituto Médico Vilafortuny, Antoni de Gimbernat Foundation, Cambrils, Spain.
J Cosmet Dermatol. 2006 Mar;5(1):87-91.
PubMed ID: 17173579

Intrinsic aging and photoaging of the face are constantly ongoing, and eventually result in the typical "aged" face, with visible lines and wrinkles at rest, a variety of dyschromia and a tired, dull and lax epidermis over poorly organized elastotic dermal architecture characterized by many interfibrillary spaces. Both ablative and nonablative resurfacing have been reported as solutions, the former providing excellent results, but a long patient downtime, and the latter giving little or no downtime, but less-than-ideal results. In ablative resurfacing, the epidermis is removed and replaced with a "new" epidermis, whereas in the nonablative approach the epidermis is spared through some form of cooling. In both approaches, however, the goal is to create controlled amounts of thermal damage in the dermis to stimulate the wound healing process, thus generating a tighter, better organized, "younger" dermal matrix. A better approach might be to apply prevention, rather than the cure, and to treat subjects in their very early 20s, before even fine lines have begun to appear.

This "photoanti-aging" approach could be achieved with the use of very low incident levels of photon energy to stimulate the skin cells, both epidermal and dermal, at cell-specific wavelengths based on the photobiological findings of the literature over the past two decades or so, in order to increase their resistance to the effects of chronological and photoaging. Lasers and IPL systems could be used, but are extremely expensive and therapist-intensive. A new generation of light-emitting diodes (LEDs) has appeared as the result of a spin-off from the US NASA Space Medicine Program, which are much more powerful than the previous generation with quasimonochromatic outputs. These LEDs can offer target specificity to achieve photobiomodulated enhanced action potentials of the skin cells, in particular mast cells, macrophages, endotheliocytes, and fibroblasts, plus increases in local blood and lymphatic flow, in a noninvasive, athermal manner. New phototherapeutic LED-based systems have appeared to meet the need for a less-expensive but clinically useful light source to enable photoantiaging as a reality in clinical practice. Some studies proving the efficacy of LED therapy have already appeared, and based on their results LED therapy represents a potential new approach to prevention in anti-aging, so that further studies are warranted to prove its efficacy.

“Effective Therapy of Low Level Laser in 810nm Wavelength on Severe Acne”

Y-H Hou, Y-Q Hou, X Fang
Division of Physiotherapy Laser-Acu-Dermatology, Guangzhou TCM Hospital, Guangzhou 510130 China . Email:

Objective: To explore the effective treatment of low level Laser (LLL) in 810 nm wavelength at 186 cases with severe acne in a face, an upper chest, a neck and an upper back, in both ways of local lighting and acupointing around loci, on the basis of a general antibiotic formula. Methods: 186 patients with severe acne were selected from the department of outpatient in the hospital, and the sex ratio was 1:1.5 (male: female), ranged age from 17-58 years old (mean age 31.25±8.63). Before treatment, all cases were scored according to the assessing schedule of 4-point, and those with serious heart problems, chronic infectious disorders and long-term use of corticosterone drug were ruled out of the trial. A sham placebo and single antibiotic groups were carried out throughout the trial. The Laser treatment device, 810 nm wavelength, work power 5-1200 nw, and effect power 4-8 Joules / cm2 , was produced by Sandon Co. in Seoul, South Korea. Every treatment included the acupointing around loci 5 minutes per point and locally lesion lighting 10 minutes per area, and a course consisted of at least 6 treatments with the program once a day. Then, the therapeutic trial was assessed as the above schedule went after two courses were finished. Results: The mixed remedy of both Low level laser with antibiotic formula produced better response, total effective rate 96.45±13 % and fail rate 3.46±2.53 %, than the sham placebo and single antibiotic control groups. Meanwhile, it also showed less scar formation and hypopigmentation or even skin whitening than both control groups did. (see Table and Fig) Conclusion: The results suggest that low level laser treating severe acne had cosmetically an efficacy against scar formation and hyperpigmentation in post-inflammation of acne by the ways of locally lesion lighting and acupointing by low level laser. It further demonstrates that LLL remedy will be an alternative physiotherapy available for some inflammatory lesions of severe acne.

“Effect of low-level laser irradiation and epidermal growth factor on adult human adipose-derived stem cells.”

Mvula B, Moore TJ, Abrahamse H.
Laser Research Group, Faculty of Health Science, University of Johannesburg, Doornfontein, Johannesburg, 2028, South Africa.
Lasers Med Sci. 2009 Jan 27.
PubMed ID: 19172344

The study investigated the effects of low-level laser radiation and epidermal growth factor (EGF) on adult adipose-derived stem cells (ADSCs) isolated from human adipose tissue. Isolated cells were cultured to semi-confluence, and the monolayers of ADSCs were exposed to low-level laser at 5 J/cm(2) using 636 nm diode laser. Cell viability and proliferation were monitored using adenosine triphosphate (ATP) luminescence and optical density at 0 h, 24 h and 48 h after irradiation. Application of low-level laser irradiation at 5 J/cm(2) on human ADSCs cultured with EGF increased the viability and proliferation of these cells. The results indicate that low-level laser irradiation in combination with EGF enhances the proliferation and maintenance of ADSCs in vitro.

“Nonablative laser and light therapies for skin rejuvenation.”

Kim KH, Geronemus RG.
Laser and Skin Surgery Center of New York, 317 E. 34th Street, New York, NY 10016, USA.
Arch Facial Plast Surg. 2004 Nov-Dec;6(6):398-409.
PubMed ID: 15545535

BACKGROUND: Multiple modalities have been described for skin rejuvenation, including ablative and nonablative therapies. Because of the prolonged recovery period associated with ablative procedures that injure the epidermis, nonablative skin treatments have grown increasingly popular. Various laser- and light-based systems have been designed or applied for promoting skin remodeling without damage to the epidermis. METHODS: Studies investigating the use of nonablative procedures for facial rhytids or acne scarring with clinical, histological, and objective quantitative measurements are systematically reviewed. RESULTS: Nonablative treatments are associated with clinical and objective improvements for the treatment of facial rhytids and acne scarring. Dermal remodeling seems to occur as a result of thermal injury, leading to dermal fibrosis without epidermal disruption. CONCLUSIONS: Although results are not as impressive as those of ablative treatments, nonablative procedures are effective in the treatment of photoaging and acne scarring. As technology in nonablative therapies continues to evolve, future laser and light sources may yield even more favorable.

“Acne vulgaris: lasers, light sources and photodynamic therapy--an update 2007.”

Gold MH.
Gold Skin Care Center, Tennessee Clinical Research Center, 2000 Richard Jones Road, Suite 220, Nashville, TN 37215, USA.
Expert Rev Anti Infect Ther. 2007 Dec;5(6):1059-69.
PubMed ID: 18039088

Inflammatory acne vulgaris remains one of the most common dermatologic disorders seen in clinical practice. Medical therapy remains the gold standard for therapy but recent advances have shown that a variety of lasers and light sources may be useful in the treatment of inflammatory acne vulgaris. In addition, the use of 20% 5-aminolevulinic acid has found a useful niche in the treatment of moderate-to-severe inflammatory acne vulgaris.

“Update on non-ablative light therapy for rejuvenation: a review.”

Sadick NS.
Clinical Professor of Dermatology, Weill Medical College of Cornell University, Ithaca, New York, USA.
Lasers Surg Med. 2003;32(2):120-8.
PubMed ID: 12561045

BACKGROUND AND OBJECTIVES: Non-ablative technologies are playing an increasing role in the management of photoaging. Newer radiofrequency technologies have added to this therapeutic armamentarium. Shorter wavelength technologies are more effective in targeting pilosebaceous vascular and pigmentary alterations while longer wavelength technologies are most effective in wrinkle reduction mediated through dermal remodeling. An overview of the various technologies available to the practicing laser surgeon are outlined in the present review. Copyright 2003 Wiley-Liss, Inc.

Online Publications    

"Low Level Laser Light Therapy (LLLT) in the Treatment of Hair Loss in Men and Women"

by Richard Giannotto, MD

"Mechanisms of Low Level Light Therapy"

by Michael R. Hamblin
Department of Dermatology, Harvard Medical School

"Basic Photomedicine"

by Ying-Ying Huang, et al
Department of Dermatology, Harvard Medical School

"Low-Level Laser or LED Therapy is Phototherapy"

by Kendric C. Smith
Stanford University School of Medicine

"Action Spectra: Their Importance for Low Level Light Therapy"

by Tiina Karu
Laboratory of Laser Biomedicine Institute of Laser and Information
Technologies, Russian Academy of Sciences       Articles       "Pivotal Clinical Data Published for the Only Laser Phototherapy Device Cleared by the FDA for Hair Growth"
Press Release, Apr 20, 2009

"Healing with Light Moves Beyond Fiction"

by Dan Ullrich
for HealthLink, online publication of the Medical College of Wisconsin
March 11, 2004

"Low level laser therapy"

From Wikipedia, the free encyclopedia

“Thinning On Top? Lasers Hold Promise”

By Jack Smith
The New York Times
Published June 20, 2005

“Reverse Your Losses”

By Jenna Bergen
Men’s Health
February, 2008 Volume 23, Page 94


by Camille Noe Pagán
Women’s Health Magazine



The Laser Therapy Handbook: A Guide for Research Scientists, Doctors, Dentists, Veterinarians and Other Interested Parties Within the Medical Field

Tunér, J. and Hode, L., (2002), pp 570 with 1400 Refs.
Prima Books AB, Grängesberg, Sweden
“The body of knowledge regarding the properties and uses of laser devices continues to expand and improve our understanding of the mechanisms involved. Several recent developments have expanded and intensified interest in furthering clinical applications in dentistry, dermatology, wound healing and other disciplines. The recent FDA approval of a few low power devices for LLLT is beginning to intensify interest in the United States. Work in these areas has been ongoing elsewhere in the world for more than 30 years.

Tunér and Hode have provided the reader with an excellent text which presents current information on a diverse array of laser related topics with a sound description of laser physics, light profiling and dosimetry. This second edition volume is a major advance over the predecessor, published in 1999.”

Reviewed by: Raymond J. Lanzafame, MD, MBA, FACS
Clinical Journal of Laser Medicine & Surgery

Ten Lectures on Basic Science of Laser Phototherapy

Tiina Karu, (2002)
Prima Books AB, Grängesberg, Sweden

 “…Low Level Light Therapy, whether using lasers or light emitting diode devices, has had a checkered history. Many people untrained in photobiology, or even science in general, started using lasers to treat everything, and claimed ‘‘miracles’’ that were unsupported by the facts. This has had a bad effect on the field of Low Level Light Therapy, such that it has been largely ignored by the main stream of science and medicine (particularly in the United States), to the detriment of the welfare of patients who could benefit from this treatment, when performed appropriately.

Fortunately, a few highly qualified scientists have worked in this field to determine how Low Level Light Therapy works at the cellular and biochemical levels. The leading scientist in this area is Dr. Tiina Karu, and the author of this book.

In this book, Dr. Karu not only reviews her own wealth of research, but she also provides an extensive review of the literature on Low Level Light Therapy…

…In classical photobiology, the photoreceptors for such things as photosynthesis, phototropism, photomovement, photoperiodism and vision have been studied for many decades. However, little attention has been given to the study of the photoreceptor(s) for Low Level Light Therapy. However, Dr. Karu has identified cytochrome c oxidase in mitochondria as the receptor, and has performed numerous studies on this enzyme that catalyzes the final step in the mitochondrial respiratory chain (the transfer of electrons from cytochrome c to molecular oxygen), and the cascade of molecular events that follow the absorption of light, which lead to the observed biological effect.

Low Level Light Therapy has been found, e.g. to reverse the detrimental effects of certain toxic chemicals in the eye, stimulate the recovery of damaged peripheral nerves and spinal cord, stimulate the healing of oral mucositis that results from anticancer therapy, the healing of chronic ulcers in the legs of diabetic patients and the treatment of pain.

A number of phototherapy studies have also been performed at the cellular level, e.g. the stimulation by light of the adhesion of mammalian cells to glass (laboratory test system), improving the fertility of sperm, stimulating the proliferation of satellite (stem) cells, and stimulating DNA and RNA synthesis.

Using the cDNA microarray technique, when human fibroblasts were irradiated at 628 nm, 111 genes were up-regulated. Most of these genes were those that directly or indirectly play roles in the enhancement of cell proliferation, and the suppression of apoptosis.

The magnitude of the Low Level Light Therapy effect is dependent upon the initial redox status of the cells. The response is stronger when the redox potential of the target cells is in a more reduced state. The response to light is weak or absent when the overall redox potential of a cell is optimal or near-optimal for the particular growth conditions. These facts help explain why the results for Low Level Light Therapy may differ from experiment to experiment, and investigator to investigator, and why sometimes the results are negative (cells were in an optimal state). Of course, there are other reasons for false-negative experiments, e.g. wrong wavelength, wrong dose, poor experimental design, etc.

Much of the book is devoted to experiments to determine the optimum use of light, e.g. pulsed vs continuous wave light, coherent vs noncoherent light, polarized vs nonpolarized light, monochromatic vs dichromatic light, single vs consecutive irradiation, dose and intensity effects, optimum techniques for irradiating cells, lasers vs conventional light sources, and of course, the effect of wavelength, by determining action spectra (the relative effectiveness of wavelengths between 600 and 850 nm).

Another large section of the book is devoted to identifying the photoreceptor(s) for Low Level Light Therapy, and studying the molecular basis for their action, determining the multiple functions of mitochondria (where cytochrome c oxidase resides), explaining cellular signaling pathways, and studying cell proliferation.

Some may find this book difficult to read, as some sections are written more like a scientific paper than a general lecture. Although the experts will appreciate all the formulas, the nonexperts will appreciate the summaries at the end of each chapter, which give the ‘‘take home lesson.’’

This reviewer hopes that this book will stimulate further scientific studies on Low Level Light Therapy, so that this therapy will be more widely accepted, and be used in a responsible manner.”

Reviewed by: Kendric C. Smith
Radiation Oncology (Radiation Biology)
Stanford University School of Medicine
Founding President, American Society for Photobiology