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A century of research
A Nobel Prize in 1903, an accidental discovery in Budapest in 1967, a NASA programme, then twenty years of clinical trials. Here is that history with its sources — and, just as importantly, with what it does not yet prove.
From lab accident to controlled trial
Every milestone links to its original source. Scientific papers open on their DOI, the permanent identifier of the article — not on a second-hand summary.
Denmark's Niels Ryberg Finsen receives the Nobel Prize in Physiology or Medicine for treating lupus vulgaris — tuberculosis of the skin — with concentrated light. Phototherapy enters medicine through the front door.
NobelPrize.org ↗In Zur Quantentheorie der Strahlung, Albert Einstein describes stimulated emission: one photon can trigger a second, identical one. Nobody will build a laser for another forty-three years, but the theory is on paper.
Theodore Maiman fires a working ruby laser at Hughes Research Laboratories and publishes the result in Nature. Light becomes an instrument whose wavelength and intensity can be controlled.
Maiman, Nature 187, 493 (1960) ↗At Semmelweis University, Endre Mester sets out to find whether a low-power laser causes cancer in mice. It causes none — but the hair of the irradiated mice grows back faster than the control group's. Laser biostimulation has just been discovered by accident.
Mester & Mester, Photomed Laser Surg (2017) ↗LEDs originally developed to grow plants in orbit are tested on wound healing. Harry Whelan's team shows they upregulate tissue-regeneration genes. This is the decisive shift: unlike a laser, an LED can go into a consumer device.
Whelan et al., J Clin Laser Med Surg 21(2) ↗The Russian biophysicist identifies the photoacceptor: cytochrome c oxidase, the last link in the mitochondrial respiratory chain. She also shows the role nitric oxide plays in the reaction. For the first time, the effect has a mechanism rather than an observation.
Karu et al., Lasers Surg Med 36(4) ↗Roberta Chow and co-authors pool 16 randomised trials covering 820 patients with neck pain. Pain drops by nearly 20 mm on a 100 mm visual scale, and the effect holds up to 22 weeks after treatment ends. Side effects do not differ from placebo.
Chow et al., The Lancet 374(9705) ↗Twenty elite female basketball players, fourteen days, thirty minutes of whole-body irradiation each evening. The treated group improves its sleep score, its serum melatonin and its twelve-minute run performance. Small sample, but a clean result.
Zhao et al., J Athl Train 47(6) ↗Forty-four men with androgenetic alopecia, a 655 nm helmet, one session every other day for sixteen weeks. The active group gains 35 to 39 % in counted hairs versus placebo. The study is replicated in women the following year, with a 37 % gain.
Lanzafame et al., Lasers Surg Med 45(8) ↗136 volunteers, thirty sessions, two spectra compared against a control group. Skin roughness by profilometry, collagen density by ultrasound, photographs scored blind: all three measures improve. The broadband spectrum adds nothing over red alone.
Wunsch & Matuschka, Photomed Laser Surg 32(2) ↗Ernesto Leal-Junior pools thirteen randomised trials on muscle performance. Repetition counts rise, so does time to exhaustion — but only for red and infrared, applied before exercise, between 50 and 200 mW and 5 to 6 joules per spot.
Leal-Junior et al., Lasers Med Sci 30(2) ↗Michael Hamblin, of the Wellman Center for Photomedicine, synthesises fifty years of work: the photon displaces the nitric oxide that was blocking cytochrome c oxidase, electron transport resumes, ATP rises. This is still the reference cited today.
de Freitas & Hamblin, IEEE JSTQE 22(3) ↗A meta-analysis of ten trials on knee osteoarthritis concludes that laser added to rehabilitation exercise beats exercise alone on pain, stiffness and function. The important word is added: light complements movement, it does not replace it.
Ahmad et al., Physiotherapy 114 ↗The LIGHTSITE III trial follows 100 subjects with dry AMD, treated at 590, 660 and 850 nm against sham. Visual acuity in the treated group improves significantly. It is one of the most rigorous trials in the field — and it concerns a medical device, not a home appliance.
Boyer et al., Retina 44(3) ↗The field now counts thousands of publications, but doses, distances and durations vary from one trial to the next to the point where comparison gets hard. That is exactly why we publish our parameters rather than promises — see how it works and our values.
What the trials measured
We give the sample size and what was actually measured — not just the conclusion. A trial on twenty people and a meta-analysis on eight hundred do not carry the same weight.
Randomised controlled trial, 136 volunteers, 30 sessions. Collagen density measured by ultrasound and roughness by digital profilometry, with blinded photographic assessment.
Wunsch A, Matuschka K. Photomed Laser Surg 2014;32(2):93–100. DOI
Double-blind randomised trial, 42 women, 655 nm, 16 weeks at one session every other day. Hair counted photographically on a tattooed area, scored by a blinded investigator. No adverse events reported.
Lanzafame RJ et al. Lasers Surg Med 2014;46(8):601–607. DOI
Meta-analysis of 16 randomised trials against placebo or active treatment, 820 patients with acute or chronic neck pain. Side effects no different from placebo.
Chow RT et al. The Lancet 2009;374(9705):1897–1908. DOI
Meta-analysis of 13 randomised trials of sufficient methodological quality. Mean gain of 5.5 repetitions and 4.1 seconds to exhaustion, obtained mainly by applying light before exercise.
Leal-Junior ECP et al. Lasers Med Sci 2015;30(2):925–939. DOI
Meta-analysis of 14 studies on the blood marker of muscle damage. Clear effect for localised exercise, inconclusive for general exercise — a nuance most product pages leave out.
Machado AF et al. Clin J Sport Med 2020;30(3):267–274. DOI
Randomised trial on 20 athletes, 14 days, 30 minutes each evening. Pittsburgh Sleep Quality Index, serum melatonin and a 12-minute run. Small sample: treat it as a signal, not as definitive proof.
Zhao J et al. J Athl Train 2012;47(6):673–678. DOI
Meta-analysis of 10 randomised trials on knee osteoarthritis, all with good PEDro scores. Pain, stiffness and function improve when light is added to an exercise programme.
Ahmad MA et al. Physiotherapy 2021;114:85–95. DOI
Reference review from the Wellman Center for Photomedicine (Harvard) on the proposed mechanisms: photoacceptor, light-sensitive ion channels, signalling cascades. The starting point for any serious reading of the field.
de Freitas LF, Hamblin MR. IEEE J Sel Top Quantum Electron 2016;22(3). DOI
Put it into practice
We publish wavelength, irradiance and duration for every product, so you can compare them against what you have just read.
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