— The research

The science of red light.

Red and near-infrared light is one of the most-studied areas in cellular biology. For decades, universities and hospitals have asked a single question: what happens when specific wavelengths of light reach the cells of the body? This page gathers that research, with a link to every study.

SOURCE 630 nm VISIBLE RED 660 nm DEEP RED 830 nm NEAR-INFRARED SHORTER WAVELENGTH DEEPER · LONGER WAVELENGTH
Thousandsof peer-reviewed
studies on PBM
1903first Nobel Prize
for light therapy
~8 cmhow deep near-infrared
light reaches in tissue
01 — How it works

How light talks to your cells.

The whole field rests on one finding: certain wavelengths of light are absorbed deep inside your cells, where they change how those cells make and manage energy. Here's the mechanism, in four parts.

01

Light fuels the mitochondria

Red and near-infrared photons are absorbed mainly by cytochrome c oxidase — the cell's energy enzyme, deep inside the mitochondria. Absorbing that light is associated with smoother electron transport and more ATP, the fuel every cell runs on.

02

It shifts the cell's redox balance

The same light triggers a brief, controlled shift in the cell's redox signalling and has been linked to more melatonin made inside the cell — not the kind that makes you sleepy, but a local antioxidant that helps buffer oxidative stress (Reiter & Zimmerman, 2019).

03

More is not better

The dose-response is biphasic: a moderate amount stimulates the cell, while too much loses the benefit. In practice that points to short, sensible sessions — commonly on the order of ten to twenty minutes — rather than longer or more intense exposure.

04

Wavelength sets the depth

How deep the light reaches depends on its wavelength. Visible red (~630–660 nm) works nearer the surface; near-infrared (~830 nm) passes deeper into the tissue beneath. Pairing them covers both.

02 — Wavelength & depth

How deep each wavelength reaches.

Longer wavelengths reach deeper into tissue — the same physics that lets bass travel further than treble. Visible red works nearer the surface; near-infrared reaches deepest. The wavelengths below are among the most-studied in their bands.

630 nmVisible red

Acts more superficially — skin and the tissue just beneath it.

660 nmDeep red

Sits near a key absorption peak of the cell's energy machinery.

830 nmNear-infrared

Invisible and deepest-reaching — the most-studied PBM near-infrared wavelength.

03 — What researchers are exploring

The research, by theme.

Photobiomodulation is studied far beyond any single organ, because it works at the level of the cell — and every tissue is made of cells. Below are the areas researchers explore most, grouped by the everyday wellbeing they touch. Tap any study to read the original.

Recovery & inflammation

Some of the strongest light research sits in exercise science: trials and meta-analyses asking whether red and near-infrared light, used around training, is linked to less soreness and faster recovery — plus reviews of the anti-inflammatory pathways involved.

Sleep quality

Researchers have asked whether red and near-infrared light is associated with how well people sleep — including one trial using a worn near-infrared neck collar. The findings lean on self-reported sleep and are still early.

Mood & emotional balance

A Harvard-led group and others have run trials shining near-infrared light at the forehead and tracking mood. The picture is genuinely mixed — some trials and a pooled analysis report a signal, a larger sham-controlled trial found none.

Stress & relaxation

Small studies have explored whether near-infrared light directed at the forehead is associated with lower self-reported anxiety and a greater sense of calm. The work is early, the samples are small, and no large trial has yet confirmed the effect.

Mental clarity & focus

Among the most-replicated findings: single sessions of forehead near-infrared light associated with faster reaction times, better attention and working memory in healthy adults — though reviewers stress the trials are small and not all randomized.

Cellular energy & vitality

This is where the mechanism lives. Reviews describe how light absorbed in the mitochondria is associated with more available cellular energy (ATP); exercise trials then test whether that shows up as less fatigue.

Skin & collagen

The best-controlled red-light trials are in skin. Split-face and placebo-controlled studies have reported increases in collagen density and smoother, less-lined skin in treated areas.

Thyroid-area research

Interest in light over the neck traces mainly to one Brazilian group, who ran a series of trials — including randomized, placebo-controlled ones — applying 830 nm light over the neck, and followed participants for years afterward. It remains early, single-group work.

04 — A short history

Light therapy isn't new.

It's older than most people assume — and the modern, cellular understanding has been building for half a century.

  1. 1903

    Phototherapy wins a Nobel Prize

    Danish physician Niels Ryberg Finsen received the Nobel Prize in Physiology or Medicine for treating skin conditions with concentrated light — establishing light as a legitimate medical therapy.

  2. 1967

    Mester discovers laser "biostimulation"

    Hungarian surgeon Endre Mester noticed that low-power laser light sped hair regrowth and wound healing in mice — the first demonstration of photobiostimulation, and the seed of low-level laser therapy.

  3. 1990s

    NASA brings LEDs into the field

    Through SBIR-funded research, NASA and Dr. Harry Whelan adapted plant-growth LED technology for human tissue, showing LED light could speed cell growth — moving the field beyond lasers to practical LED devices.

  4. 2001

    Clinical evidence for LED light

    Whelan's team published research showing NASA-developed LED irradiation promoted faster wound healing, with treated cells growing markedly faster than controls — broadening interest in non-laser light sources.

  5. 2015

    The field is formally renamed

    "Photobiomodulation" was adopted as an official U.S. National Library of Medicine MeSH term, retiring the vague "low-level laser therapy" and acknowledging that LEDs and other light sources are now widely used.

  6. Today

    A maturing evidence base

    Photobiomodulation is now backed by thousands of peer-reviewed studies and ongoing clinical trials, with research into its mechanisms and applications continuing to expand worldwide.

Full reference list
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  2. Karu TI. Multiple roles of cytochrome c oxidase in mammalian cells under action of red and IR-A radiation. IUBMB Life. 2010. PMID 20681024.
  3. Huang YY, Chen ACH, Carroll JD, Hamblin MR. Biphasic Dose Response in Low Level Light Therapy. Dose-Response. 2009. PMID 20011653.
  4. Zimmerman S, Reiter RJ. Melatonin and the Optics of the Human Body. Melatonin Research. 2019. doi:10.32794/mr11250016.
  5. Vanin AA, Verhagen E, Barboza SD, Costa LOP, Leal-Junior ECP. Photobiomodulation therapy for the improvement of muscular performance and reduction of muscular fatigue associated with exercise in healthy people: a systematic review and meta-analysis. Lasers Med Sci. 2018. PMID 29090398.
  6. Luo WT, Lee CJ, Tam KW, Huang TW. Effects of Low-Level Laser Therapy on Muscular Performance and Soreness Recovery in Athletes: A Meta-analysis of Randomized Controlled Trials. Sports Health. 2022. PMID 34428975.
  7. Nampo FK, Cavalheri V, Ramos SP, Camargo EA. Effect of low-level phototherapy on delayed onset muscle soreness: a systematic review and meta-analysis. Lasers Med Sci. 2016. PMID 26563953.
  8. Hamblin MR. Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS Biophysics. 2017. PMID 28748217.
  9. Zhao J, Tian Y, Nie J, Xu J, Liu D. Red Light and the Sleep Quality and Endurance Performance of Chinese Female Basketball Players. J Athl Train. 2012. PMID 23182016.
  10. Kennedy KER, Wills CCA, Holt C, Grandner MA. A randomized, sham-controlled trial of a novel near-infrared phototherapy device on sleep and daytime function. J Clin Sleep Med. 2023. PMID 37141002.
  11. Gaggi NL, Parincu Z, Peterson A, et al. Enhancing sleep, wakefulness, and cognition with transcranial photobiomodulation: a systematic review. Front Behav Neurosci. 2025. PMID 40822571.
  12. Cassano P, Petrie SR, Mischoulon D, et al. Transcranial Photobiomodulation for the Treatment of Major Depressive Disorder: The ELATED-2 Pilot Trial. Photomed Laser Surg. 2018. PMID 30346890.
  13. Ji Q, Yan S, Ding J, et al. Photobiomodulation improves depression symptoms: a systematic review and meta-analysis of randomized controlled trials. Front Psychiatry. 2024. PMID 38356614.
  14. Iosifescu DV, Norton RJ, Tural U, et al. Very Low-Level Transcranial Photobiomodulation for Major Depressive Disorder: The ELATED-3 Multicenter, Randomized, Sham-Controlled Trial. J Clin Psychiatry. 2022. PMID 35950904.
  15. Salehpour F, Mahmoudi J, Kamari F, Sadigh-Eteghad S, Rasta SH, Hamblin MR. Brain Photobiomodulation Therapy: a Narrative Review. Mol Neurobiol. 2018. PMID 29327206.
  16. Maiello M, Losiewicz OM, Bui E, et al. Transcranial Photobiomodulation with Near-Infrared Light for Generalized Anxiety Disorder: A Pilot Study. Photobiomodul Photomed Laser Surg. 2019. PMID 31647775.
  17. Helali H, Samani N, Tabeie F, Eiliaei S, Kheradmand A. The effectiveness of transcranial photobiomodulation therapy (tPBM) on reducing anxiety, depression, and opioid craving in patients undergoing methadone maintenance treatment: a double-blind, randomized, controlled trial. BMC Psychiatry. 2025. PMID 39901090.
  18. Caldieraro MA, Cassano P. Transcranial and systemic photobiomodulation for major depressive disorder: A systematic review of efficacy, tolerability and biological mechanisms. J Affect Disord. 2019. PMID 30248638.
  19. Barrett DW, Gonzalez-Lima F. Transcranial infrared laser stimulation produces beneficial cognitive and emotional effects in humans. Neuroscience. 2013. PMID 23200785.
  20. Blanco NJ, Maddox WT, Gonzalez-Lima F. Improving executive function using transcranial infrared laser stimulation. J Neuropsychol. 2017. PMID 26017772.
  21. Salehpour F, Majdi A, Pazhuhi M, et al. Transcranial Photobiomodulation Improves Cognitive Performance in Young Healthy Adults: A Systematic Review and Meta-Analysis. Photobiomodul Photomed Laser Surg. 2019. PMID 31549906.
  22. Lee TL, Ding Z, Chan AS. Can transcranial photobiomodulation improve cognitive function? A systematic review of human studies. Ageing Res Rev. 2023. PMID 36371017.
  23. Hamblin MR. Mechanisms and Mitochondrial Redox Signaling in Photobiomodulation. Photochem Photobiol. 2018. PMID 29164625.
  24. Leal-Junior ECP, Vanin AA, Miranda EF, de Carvalho PdT, Dal Corso S, Bjordal JM. Effect of phototherapy (low-level laser therapy and light-emitting diode therapy) on exercise performance and markers of exercise recovery: a systematic review with meta-analysis. Lasers Med Sci. 2015. PMID 24249354.
  25. Bezerra LO, de Macedo LES, da Silva MLA, et al. Effects of photobiomodulation therapy on the functional performance of healthy individuals: a systematic review with meta-analysis. Lasers Med Sci. 2023. PMID 38150056.
  26. Rossato M, Dellagrana RA, Sakugawa RL, Baroni BM, Diefenthaeler F. Dose-Response Effect of Photobiomodulation Therapy on Muscle Performance and Fatigue During a Multiple-Set Knee Extension Exercise: A Randomized, Crossover, Double-Blind Placebo-Controlled Trial. Photobiomodul Photomed Laser Surg. 2020. PMID 33232629.
  27. Wunsch A, Matuschka K. A controlled trial to determine the efficacy of red and near-infrared light treatment in patient satisfaction, reduction of fine lines, wrinkles, skin roughness, and intradermal collagen density increase. Photomed Laser Surg. 2014. PMID 24286286.
  28. Lee SY, Park KH, Choi JW, et al. A prospective, randomized, placebo-controlled, double-blinded, and split-face clinical study on LED phototherapy for skin rejuvenation. J Photochem Photobiol B. 2007. PMID 17566756.
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  30. Le Thi Nhu Ngoc, Moon JY, Lee YC. Utilization of light-emitting diodes for skin therapy: Systematic review and meta-analysis. Photodermatol Photoimmunol Photomed. 2023. PMID 36310510.
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Every reference links to its record on PubMed.

This page summarises independent, peer-reviewed research on photobiomodulation and red/near-infrared light, for educational purposes only. It describes studies of light in general, not any specific product, and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. Always consult a qualified healthcare professional before making changes to your health routine.