The Science Behind Red Light Therapy
The idea that light can support biological processes is not new.
It earned a Nobel Prize over a century ago, drove NASA research in the 1990s, and today underpins a growing body of peer reviewed science.
The scientific term for it is photobiomodulation — but it's the same thing as red light therapy. Different name, same science..
At Red Light Rising, we build every device around this research — selecting specific wavelengths, power outputs, and dosing parameters based on what the evidence actually supports.
This page explains the science in plain language, references the key studies, and helps you understand why wavelength, distance, and timing matter.
A Nobel Prize For Light As Medicine
In 1903, Danish physician Niels Ryberg Finsen got the Nobel Prize in Physiology or Medicine for demonstrating that concentrated light radiation could be used to address skin conditions, specifically lupus vulgaris.
Finsen was himself chronically ill — he spent his final years in a wheelchair, and his personal experience with the effects of light and darkness on his own energy levels inspired his research.
While Finsen's work used UV wavelengths rather than the red and near infrared light used today, his contribution established a foundational principle: that light itself can influence biological processes.
Over 40 Finsen Institutes were established across Europe following his work, and phototherapy became an accepted branch of medicine.
The Hungarian Physician And The Ruby Laser
More than sixty years passed between Finsen's Nobel Prize and the next major chapter in the story.
In 1967, a Hungarian physician named Endre Mester at Semmelweis Medical University in Budapest got hold of a newly invented ruby lasers and decided to test whether laser radiation could cause cancer in mice.
He shaved the hair from their backs, divided them into two groups, and aimed the 694nm laser at one group.
The laser was too weak to do much of anything harmful — it certainly didn't cause cancer.
But Mester noticed something he wasn't expecting.
The hair on the treated mice grew back noticeably faster than on the untreated group.
And the cuts he'd made to transplant experimental tumours were healing more quickly in the laser treated mice too.
He called it "laser biostimulation" and published his findings that same year.
The paper, written in Hungarian, appeared in Kiserl Orvostud in 1967 (Mester E, Szende B, Tota JG. "Effect of laser on hair growth of mice." Kiserl Orvostud. 1967;19:628-631).
It remains one of the most cited papers in the entire field. Mester went on to publish over 100 papers on the biological effects of low power laser light, founded the Laser Research Center at Semmelweis in 1974, and continued working there until his death in 1984.
What makes Mester's story important is the accidental nature of the discovery.
He wasn't looking for a therapeutic effect. He was trying to cause cancer!
The fact that a low powered laser could stimulate tissue repair rather than damage it was completely unexpected and it took decades for the rest of the medical world to take it seriously.
The field he accidentally founded is now called photobiomodulation, and the highest honour in the discipline — the Endre Mester Lifetime Achievement Award — bears his name.
Michael Hamblin received the first one in 2017.
NASA And The Accidental Discovery
In the late 1980s, researchers at NASA's Marshall Space Flight Center began studying red LEDs for growing plants in space.
The goal was to drive photosynthesis in microgravity.
In October 1995, an LED plant growth unit went into space on the Space Shuttle Columbia, successfully growing potatos using red and blue LEDs during a 16 day mission.
The unexpected finding came from the researchers themselves — scientists working under red LED light panels noticed that cuts and injuries on their hands appeared to be clearing faster than expected.
This observation triggered a formal investigation led by Dr Harry Whelan at the Medical College of Wisconsin, funded by eight NASA research contracts between 1995 and 2003.
Whelan's team studied LEDs at 670nm, 720nm, and 880nm and reported significant increases in cell growth of fibroblasts, osteoblasts, and skeletal muscle cells.
The research was recognised with entry into the Space Technology Hall of Fame in 2000, and the landmark findings were published in the Journal of Clinical Laser Medicine and Surgery in 2001 (PMID: 11776448).
From Lasers To LEDs
Early phototherapy devices used expensive and dangerous lasers that were impractical for home use.
The shift to light emitting diodes (LEDs) changed everything.
LEDs can deliver the same therapeutic wavelengths as lasers, at a fraction of the cost, across much larger surface areas, and with an excellent safety profile.
This made it possible to build affordable full body panels, flexible wraps, and portable handheld devices that deliver clinical grade dosing outside a medical setting.
Today, photobiomodulation (red light therapy) is one of the fastest growing areas of wellness and longevity research, with thousands of published studies exploring how specific wavelengths of red and near infrared light may support cellular function.
How Red Light Therapy Works at The Cellular Level
Mitochondria and the energy your cells run on
Every cell in your body contains mitochondria — small structures responsible for producing the energy molecule adenosine triphosphate (ATP).
ATP powers almost every biological process you can name: muscle contraction, tissue repair, immune function, collagen production, nerve signalling.
When mitochondria are functioning well, your cells have the energy they need to do their jobs. When mitochondrial function declines (through ageing, stress, illness, or chronic inflammation) cells become less efficient and recovery slows down.
This is where red and near infrared light enters the picture.
Cytochrome c oxidase — the key enzyme
The mechanism that underpins red light therapy centres on an enzyme called cytochrome c oxidase (CCO), which sits at unit IV of the mitochondrial electron transport chain.
CCO is the final step in the process that produces ATP. It contains both heme and copper centres, and it absorbs light in the red and near infrared spectrum — roughly between 600nm and 900nm.
The leading hypothesis, supported by extensive research from Dr Michael Hamblin and others, is that nitric oxide (NO) builds up on cytochrome c oxidase over time and acts as an inhibitor — essentially blocking the enzyme and slowing down energy production.
When red or near infrared photons are absorbed by CCO, they dissociate the nitric oxide from the enzyme, removing the blockage.
This restores normal electron transport, increases mitochondrial membrane potential, and allows the cell to produce ATP more efficiently (de Freitas and Hamblin, 2016, PMID: 28070154).
In simple terms: the light removes a molecular brake and lets the engine run properly again.
What happens after the photons arrive
The dissociation of nitric oxide from CCO is the initial event — but it triggers a cascade of downstream effects.
The freed nitric oxide itself is a signalling molecule that supports local blood flow and circulation.
Meanwhile, the increase in mitochondrial activity generates small amounts of reactive oxygen species (ROS), which act as cellular messengers.
These ROS activate transcription factors — proteins that switch on specific genes. The result is increased expression of genes related to protein synthesis, cell migration, cell proliferation, anti-inflammatory signalling, and antioxidant enzyme production (Hamblin, 2018, PMID: 29164625).
This is why the effects of red light therapy extend beyond the immediate treatment area and session time. The light provides the initial stimulus, but the biological response unfolds over hours and days as gene expression changes and the cell adapts.
The sunlight connection — nature's missing piece
Humans evolved under natural sunlight, which contains a significant proportion of red and near infrared wavelengths.
In fact, roughly 40% of the solar spectrum that reaches the earth's surface is near infrared — invisible to the eye but present in large quantities during every hour of daylight.
Modern life has fundamentally changed our relationship with light.
We spend the majority of our time indoors, behind glass that filters out much of the infrared spectrum, under artificial lighting that provides almost none of it.
The average person in the UK spends over 90% of their time inside.
The argument for red light therapy is not that it introduces something new to human biology.
It's that it restores something we've lost.
Our mitochondria evolved to receive daily red and near infrared light from the sun. We no longer get that.
Red light therapy devices deliver those same wavelengths in a controlled, convenient, and measurable way.
This doesn't mean red light therapy replaces sunlight — nothing does.
But it may help compensate for the fact that our modern indoor lifestyles deprive our cells of a light stimulus they were built to receive.
The dose matters — the biphasic response
One of the most important concepts in photobiomodulation is the biphasic dose response, sometimes referred to as the Arndt-Schulz curve.
The principle is straightforward: too little light produces no meaningful effect.
The right amount produces a positive biological response.
Too much light can actually reduce or reverse that benefit (Huang et al., 2009, PMID: 20011653).
This means more is not always better.
A 5 minute session at the right distance may produce a better outcome than a 30 minute session at the same distance. The optimal dose depends on the wavelength, the power density of the device, the distance between the device and your body, and the specific tissue being targeted.
This is why our product guides include recommended session times and treatment distances for each device — they're based on published dosing parameters, not arbitrary numbers. Getting the dose right is what separates an effective protocol from a waste of time.
Wavelengths and What They Target
Not all red light is the same.
The wavelength — measured in nanometres (nm) — determines how deep the light penetrates into your body and which cellular structures it interacts with.
This matters because a device built for skin care needs different parameters than one designed for joint support or eye comfort.
Here's what the research tells us about the wavelengths we use.
| Wavelength | Type | Penetration Depth | Primary Applications |
|---|---|---|---|
| 630nm | Visible red | 1 to 4mm (epidermis and upper dermis) | Skin rejuvenation, surface circulation, complexion |
| 660nm | Visible red | 2 to 5mm (full dermal layer) | Collagen support, skin texture, surface tissue wellness |
| 670nm | Visible red | 2 to 5mm (retinal delivery via the pupil) | Eye comfort, mitochondrial support in ageing retinal cells |
| 810nm | Near infrared | 3 to 5cm under optimal conditions | Deep tissue, joints, muscles, transcranial applications |
| 850nm | Near infrared | 3 to 5cm | Deep tissue, joints, muscles, general cellular wellness |
Penetration depths are approximate and vary depending on tissue type, skin pigmentation, and the amount of blood flow in the area. Near infrared wavelengths are invisible to the naked eye.
A note on wavelength overlap
Most published studies test one wavelength at a time.
That's how controlled research works — you isolate the variable.
But it can give the impression that 660nm does one thing and 850nm does something completely different, and that only the exact wavelength tested in a given study will produce that specific result.
The reality is more nuanced. The expert consensus is that wavelengths within the same band, red or near infrared, produce broadly similar and overlapping benefits.
A 660nm LED and a 670nm LED are not fundamentally different devices.
They sit within the same absorption range of cytochrome c oxidase and interact with the same cellular structures.
The same is true across the near infrared range — 810nm, 830nm, and 850nm all penetrate to similar depths and act through similar mechanisms.
This doesn't mean wavelength is irrelevant.
There are meaningful differences in penetration depth between red and near infrared, and certain wavelengths align more closely with specific absorption peaks. But within each band, the differences are gradual rather than binary.
If a study shows a positive result at 660nm, it would be surprising if 670nm produced nothing at all.
Biology doesn't work like a combination lock.
Near infrared light may go much further than we thought
The penetration depths in the table above are based on decades of established research. But a 2025 study from Professor Glen Jeffery's team at UCL may have rewritten the rules entirely.
In this study, published in Scientific Reports (Jeffery et al., 2025, PMID: 40628952), researchers placed a radiometer against participants' torsos in direct sunlight and measured which wavelengths came out the other side.
Near infrared light — specifically in the 830 to 860nm range — passed through the entire human thorax.
They then recreated this in the lab using LED panels delivering 830 to 860nm light to participants' backs for 15 minutes.
Vision improved measurably 24 hours later, even in participants whose eyes were completely shielded from the light.
Clothing reduced the intensity slightly but did not block it.
The implication is significant.
Near infrared light may not just penetrate a few centimetres into local tissue — it may pass through the body entirely and produce systemic effects on distant organs and tissues.
If confirmed by further research, this changes how we think about the relationship between where you aim a device and what it can affect.
It also reinforces the sunlight argument — if you're outside, near infrared wavelengths from the sun are reaching deep into your body whether you realise it or not.
Why we chose these specific wavelengths
Every wavelength in our range exists for a reason.
The 670nm in the Target Light 670 is there because of Professor Glen Jeffery's research at University College London showing that this specific wavelength may support mitochondrial function in ageing retinal cells.
The 660nm and 850nm combination in the Target Light 2.0, Target Light 4.0 and the Advantage Wrap covers both surface and deep tissue in a single session.
The 810nm and 830nm in the Target Light 3.0 and our Advantage panels sit at the point where tissue is most transparent to light — the absolute sweet spot of the optical window where melanin, haemoglobin, and water absorption are all at their lowest.
We don't add wavelengths for the sake of a longer spec sheet. Each one maps to published research and a specific use case.
What the research suggests by benefit area
The evidence base for photobiomodulation varies by application.
Some areas have strong clinical trial data.
Others are earlier in the research cycle with promising but smaller studies.
We think it's important to be honest about where the science stands rather than overpromising.
Skin and collagen — strong evidence. A controlled trial of 136 volunteers found that red light between 611nm and 650nm applied twice weekly for 30 sessions was associated with measurable improvements in intradermal collagen density on ultrasonography (Wunsch and Matuschka, 2014, PMID: 24286286).
A separate study using 660nm LED light found a 31% increase in type 1 procollagen — the precursor to collagen — in a tissue model (Barolet et al., 2009, PMID: 19587693). This is why our 660nm devices are positioned for skin and complexion support.
Joints and muscles — moderate to strong evidence.
A 2024 systematic review of 13 randomised controlled trials involving 673 participants found that low level light therapy (LLLT a.ka red light therapy) was associated with meaningful improvements in knee comfort for people with osteoarthritis, with 810nm showing the most promising results (PMID: 39367994).
For muscle support, a meta-analysis found that phototherapy applied before exercise was associated with increased time to exhaustion and reduced markers of muscle stress (Leal-Junior et al., 2015, PMID: 24249354).
This is the evidence behind our near infrared wavelengths in the Advantage panels and the Advantage Wrap.
Eye comfort and mitochondrial support — emerging but compelling.
Professor Glen Jeffery's team at UCL published two studies that changed how we think about 670nm light.
The first (2020, PMID: 32596723) showed that 3 minutes of daily 670nm exposure over two weeks improved colour contrast sensitivity by up to 20% in participants aged 40 and over — particularly on the blue-yellow axis, which is the colour channel most affected by ageing.
The second (2021, PMID: 34819619) found that a single 3 minute morning exposure was enough to produce improvements lasting at least one week.
Afternoon exposure showed no benefit.
This is why the Target Light 670 exists, and why we recommend morning use.
Sleep and circadian rhythm — early research.
A small study of 20 athletes found that 14 days of nightly red light exposure was associated with improved sleep quality scores and higher melatonin levels compared to a control group (Zhao et al., 2012, PMID: 23182016).
The study is small and specific to young female basketball players, so we'd be cautious about generalising the results.
What is well established is that red wavelengths do not suppress melatonin production the way blue and white light do — which makes red light a sensible choice for evening environments.
This is the thinking behind our Dusk Lamp and our blue light blocking glasses range.
Researchers and Further Reading
Dr Michael Hamblin
If one person can be credited with establishing photobiomodulation as a legitimate scientific discipline, it's Michael Hamblin.
He spent over two decades at the Wellman Center for Photomedicine at Massachusetts General Hospital and held the position of Associate Professor of Dermatology at Harvard Medical School.
He has published over 840 peer reviewed papers with an h-index exceeding 170.
In plain terms, that means at least 170 of his papers have each been cited by other researchers at least 170 times — a measure of how influential the work is.
For context, most successful academics spend an entire career reaching an h-index of 20 or 30.
An h-index above 170 puts Hamblin among the most cited researchers in any field of medicine.
In 2017, he received the 1st Endre Mester Lifetime Achievement Award in Photomedicine — essentially the highest recognition in the field.
Hamblin's contribution is not one breakthrough study.
It's the cumulative weight of hundreds of papers that established the mechanism, defined the dose response curve, and gave the rest of the research community a framework to work within.
His reviews are the ones other researchers cite when they need to explain how photobiomodulation actually works.
He currently serves as Distinguished Visiting Professor at the University of Johannesburg.
Professor Glen Jeffery
Glen Jeffery is Professor of Neuroscience at the Institute of Ophthalmology, University College London.
His research focuses on how 670nm red light interacts with mitochondria in the retina — the tissue with the highest energy demand of any structure in the human body.
What makes Jeffery's work particularly relevant is its simplicity.
His protocol involves a small LED torch, 670nm, 3 minutes, once in the morning. That's it. And the results in his published studies have been striking — measurable improvements in colour vision in people over 40, from an intervention that costs almost nothing and takes less time than brushing your teeth.
In December 2025, Jeffery appeared as a guest on the Huberman Lab podcast, where he discussed his findings on red light and metabolism, the harmful effects of modern LED lighting, and why morning timing matters for mitochondrial response.
The episode brought his work to a much wider audience.
Further learning
The following researchers, educators, and commentators have helped bring photobiomodulation and red light therapy to a broader public audience.
They are not the primary evidence base for the claims on this page, but their work is worth exploring if you want to go deeper.
Andrew Huberman is a neuroscientist and tenured professor at Stanford University School of Medicine.
His Huberman Lab podcast has covered red and near infrared light across several episodes, most notably Episode 68 ("Using Light to Optimize Health") and his December 2025 interview with Professor Glen Jeffery.
Huberman discusses the CCO mechanism, recommends 630 to 660nm for surface applications and 810 to 850nm for deeper tissue, and emphasises morning timing for red light protocols.
He uses red lighting at night specifically because it doesn't suppress melatonin.
Jack Kruse is a neurosurgeon who writes and speaks about the relationship between light, water, and magnetism in human biology.
His perspective is broader and more speculative than the clinical research cited elsewhere on this page, but his emphasis on the importance of natural light exposure and the problems with artificial lighting environments has resonated with a large community of health conscious readers.
We'd describe his work as thought provoking rather than peer reviewed.
Key studies referenced on this page
All studies cited on this page are accessible via PubMed, the US National Library of Medicine's free database of biomedical research.
Whelan HT et al. "Effect of NASA light-emitting diode irradiation on wound healing." Journal of Clinical Laser Medicine and Surgery, 2001. PMID: 11776448.
de Freitas LF, Hamblin MR. "Proposed mechanisms of photobiomodulation or low-level light therapy." IEEE Journal of Selected Topics in Quantum Electronics, 2016. PMID: 28070154.
Hamblin MR. "Mechanisms and applications of the anti-inflammatory effects of photobiomodulation." AIMS Biophysics, 2017. PMID: 28748217.
Hamblin MR. "Mechanisms and mitochondrial redox signaling in photobiomodulation." Photochemistry and Photobiology, 2018. PMID: 29164625.
Huang YY et al. "Biphasic dose response in low level light therapy." Dose Response, 2009. PMID: 20011653.
Shinhmar H et al. "Optically improved mitochondrial function redeems aged human visual decline." Journals of Gerontology: Series A, 2020. PMID: 32596723.
Shinhmar H et al. "Weeklong improved colour contrasts sensitivity after single 670 nm exposures associated with enhanced mitochondrial function." Scientific Reports, 2021. PMID: 34819619.
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." Photomedicine and Laser Surgery, 2014. PMID: 24286286.
Barolet D et al. "Regulation of skin collagen metabolism in vitro using a pulsed 660 nm LED light source." Journal of Investigative Dermatology, 2009. PMID: 19587693.
Leal-Junior EC et al. "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 in Medical Science, 2015. PMID: 24249354.
Systematic review of LLLT for knee osteoarthritis, 2024. PMID: 39367994.
Zhao J et al. "Red light and the sleep quality and endurance performance of Chinese female basketball players." Journal of Athletic Training, 2012. PMID: 23182016.
Jeffery G, Fosbury R, Barrett E, Hogg C, Rodriguez Carmona M, Powner MB. "Longer wavelengths in sunlight pass through the human body and have a systemic impact which improves vision." Scientific Reports, 2025; 15:24435. PMID: 40628952.
Frequently Asked Questions About Red Light therapy
Is red light therapy actually backed by science? +
Yes. Photobiomodulation — the scientific term for red and near infrared light therapy — has been studied in thousands of peer reviewed papers.
The core mechanism involves an enzyme in your mitochondria called cytochrome c oxidase, which absorbs red and near infrared photons and increases ATP production.
This mechanism was first proposed by Tiina Karu at the Russian Academy of Sciences and has since been validated across hundreds of studies, including comprehensive reviews by Dr Michael Hamblin at Harvard and Massachusetts General Hospital.
The field also has roots in NASA funded research from the 1990s, where LED light at 670nm, 720nm, and 880nm was shown to increase cell growth in human tissue cultures.
None of this means red light therapy is a cure for anything — but the biological mechanism is well understood and the evidence base is substantial and growing.
Is red light therapy safe for eyes? +
The wavelengths used in red light therapy (600nm to 900nm) are non ionising and do not carry the risks associated with ultraviolet light.
For targeted eye protocols, the most studied approach is Professor Glen Jeffery's work at UCL using 670nm at very low power (around 8 mW/cm²) for just 3 minutes in the morning.
His published studies showed improvements in colour contrast sensitivity with no adverse effects reported.
For general red light therapy panels and handhelds, we recommend keeping the device at a comfortable distance (up to arms length away with our devices) from your face during sessions, and using red mode only (not near infrared) for facial sessions, as near infrared is invisible and you cannot gauge intensity by looking at the device.
If you have a pre existing eye condition, consult a healthcare professional before starting.
How often should I use red light therapy? +
Most research protocols use sessions of 5 to 15 minutes per area, 3 to 5 times per week.
Daily use is common and appears safe based on the published literature. However, more is not always better — photobiomodulation follows a biphasic dose response, meaning there is an optimal range.
Exceeding that range doesn't necessarily cause harm, but it may reduce the benefit.
We recommend starting with the session times around 5 minutes per area and building a consistent routine rather than doing long infrequent sessions.
Consistency matters more than intensity.
What wavelength is best for skin compared to joints? +
For skin, complexion, and surface tissue, red wavelengths between 630nm and 670nm are the most studied.
These penetrate the outer layers of skin where fibroblasts produce collagen and elastin.
For joints, muscles, and deeper tissue, near infrared wavelengths around 810nm to 850nm penetrate significantly further — up to several centimetres under the right conditions — reaching structures that visible red light cannot.
Many of our devices combine both red and near infrared wavelengths so you can address surface and deep tissue in a single session.
How long before I notice a difference? +
This depends entirely on what you're using it for, how consistently you use it and several other lifestyle factors.
Some people report noticing changes within a few days — particularly with skin texture and general sense of wellbeing.
Joint and muscle related benefits tend to take longer, with most studies running 2 to 4 weeks before measuring outcomes.
Professor Jeffery's eye study showed measurable improvements after 2 weeks of daily 3 minute sessions.
The honest answer is that results are typically modest and cumulative.
This is not an overnight transformation — it's a long term wellness practice, similar to exercise or nutrition.
Is red light therapy a replacement for medical treatment? +
No. Red light therapy is a wellness tool, not a medical device or a substitute for professional medical care.
It does not diagnose, treat, cure, or prevent any disease.
The research referenced on this page describes biological mechanisms and reports findings from controlled studies — it does not constitute medical advice.
If you have a specific medical condition, please consult your healthcare provider before using any red light therapy device.
We position our products as supportive wellness tools designed to be used alongside, not instead of, appropriate medical care.