In 2021, dermatologist David Ozog was on vacation with his family in the Bahamas, when his 18-year-old son suffered a serious stroke. The teen was flown to Florida and then to Chicago for surgery. As his son lay partially paralyzed in a hospital bed, Ozog received a call from a colleague who made an unconventional suggestion.
The colleague, a dermatologist at Harvard Medical School in Boston, Massachusetts, told Ozog about research he was conducting with the U.S. Department of Defense. Initial results suggest that red and near-infrared light applied to the head could protect neural tissue after brain injury. He urged Ozog to consider trying it on his son.
Ozog stayed up until 4 a.m. that night, reading scientific papers and, eventually, ordering several panels made of red and near-infrared light-emitting diodes (LEDs). “I started sneaking them into the hospital,” says Ozog, who works at Henry Ford Health in Grand Rapids, Michigan.
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Today, her son is walking and returning to college. Ozog can’t prove that light therapy made a difference, but he thinks it helped. He has since converted to an idea that, at the time, was considered fringe. “I was thinking the same thing,” he said, “How could projecting yourself with this thing have a biological effect?”
But what was still on the fringes of medicine a few years ago is now becoming common practice. Red light devices are increasingly appearing in dermatology practices, wellness centers, locker rooms and homes. By some projections, the global market will surpass $1 billion by 2030, propelled by a wave of companies promising benefits in everything from skin aging to attention deficit hyperactivity disorder (ADHD) – claims widely echoed on social media.
Experts warn that there is considerable hype around red light therapy. But a growing number of legitimate scientific works are exploring the benefits of this treatment in several pathologies. Clinical studies have reported improvements in peripheral neuropathy, retinal degeneration, and certain neurological disorders. For certain indications, expert groups now recommend red light diets.
Researchers are also discovering how red and near-infrared light might exert these effects. Mitochondria – the cell power plants– appear as a central piece of the puzzle.
The science behind these benefits is growing at a time when humans are exposed to less red light than ever before. People are spending more time indoors, away from the sun, and efforts to save energy have narrowed the spectrum of indoor lighting, eliminating many red and near-infrared wavelengths. Some scientists are now wondering whether these factors could have biological consequences. “We are literally deprived of something that, biologically, we evolved to receive,” Ozog explains.
From the margins to the clinic
The role of light in human health is not a new idea. For over a century, scientists have known that ultraviolet light causes vitamin D production. The 1903 Nobel Prize in Physiology or Medicine recognized concentrated light as a treatment for cutaneous tuberculosis. Bright light therapy is standard care for seasonal affective disorder, and narrow-band ultraviolet light remains a mainstay for psoriasis.
“The whole spectrum produces a whole range of things that are beneficial to us,” says Glen Jeffery, a neuroscientist at University College London. Modern photobiomodulation – the use of red and near-infrared light comprising wavelengths ranging from about 600 nanometers to 1,100 nanometers to influence cellular processes – emerged in the 1960s after Hungarian scientists accidentally discovered that low-intensity red light stimulated hair growth in rodents. Interest accelerated in the 1990s, when NASA scientists experimenting with using red LEDs to grow plants in space noticed that small cuts on their hands healed unusually quickly under the lights.
Over the past decade, evidence has solidified in several clinical niches. In 2025, Ozog joined more than 20 specialists in a major consensus study, which concluded that the treatment was safe and effective for several types of ulcers, peripheral neuropathy, acute radiation dermatitis and androgenic alopecia, a type of hair loss. Last year, the United States Food and Drug Administration approved a red light device for dry age-related macular degeneration. And since 2020, red light therapy in the mouth has been included in clinical guidelines to prevent and treat cancer treatment-related oral mucositis – painful mouth ulcers that can limit treatment and disrupt nutritional intake.
Ozog laments that the therapy is not more widely applied in cancer care: “Here is a simple, safe and inexpensive treatment that is probably used in about 10% of treatment centers. »
Beyond these anchors, researchers are exploring the therapy’s broader effects. Clinical trials report improved muscle recovery in athletes, as well as reduced depression symptoms and pain in people with osteoarthritis and fibromyalgia. Small human trials and animal studies also suggest potential benefits for metabolic and cardiovascular diseases. A small randomized study in Brazil, published in 2022, found that people with severe COVID-19 who received daily light therapy left the hospital on average almost four days earlier than controls.
However, for some scientists, the most striking first results concern the brain. In mouse models of Parkinson’s disease (PD), photobiomodulation applied to the top of the head preserved dopamine-producing neurons deep in the brain, cells whose loss leads to disease progression.
Researchers have found that benefits in animal models of Parkinson’s last for weeks after treatment, and the first human trials are underway, using optical fibers that bring light closer to diseased cells. “The holy grail of neuroscience research is finding an effective neuroprotective treatment that protects cells from death,” says John Mitrofanis, a neuroscientist at the University of Grenoble Alpes in France.
Several transcranial devices are under development that could offer more practical delivery of photons, to treat various psychiatric and neurological diseases. Unpublished results from Mitrofanis’ team suggest that transcranial light “makes an older brain look like a younger brain,” he says. Yet getting enough photons through the human skull to produce a significant effect remains a challenge. Brian Pryor, chief executive of BWtek Medical, a medical device company based in Newark, Delaware, says his team has found that higher doses of photons have a greater impact on the brain. Devices with such high wattages “may be too powerful to sell over the counter,” he says. Several other clinical trials are planned or are currently underway.
Much remains unresolved: wavelengths, intensities, timing, delivery methods, and even optimal pulse rates for different indications. It’s also unclear whether people’s age or skin color should determine the dose they receive. And behind all this lies a deeper question: how can light produce biological effects of such magnitude?
Transforming light into cellular fuel
Converging lines of biophysical and biochemical evidence have led researchers to focus on mitochondria, the energy-producing organelles found in most cells in the body.
Red to near-infrared light wavelengths scatter much less than shorter blue and ultraviolet wavelengths. As a result, some photons – mainly near-infrared ones – can pass through clothing and a fraction can penetrate a few centimeters into tissue, increasing the possibility that they will affect cells well beneath the skin. Wavelengths between 600 and 700 nanometers and between 760 and 940 nanometers are often reported to produce biological responses. These ranges closely correspond to the wavelengths most easily absorbed by cytochrome c oxidase, a key enzyme in the mitochondrial electron transport chain that contributes to the formation of the cellular fuel called adenosine triphosphate (ATP).
Evidence suggests that cells can absorb these wavelengths and that the light pushes the electron transport chain toward a more active state, thereby stimulating ATP production. Downstream effects include improved blood flow and changes in inflammation and oxidative stress. Some researchers have proposed an additional mechanism: red and near-infrared light reduce the viscosity of water, allowing power-producing machines to move more easily. “For the mitochondrial engine to function properly, it needs a lubricant,” says Robert Fosbury, an astronomer turned photobiomodulation researcher at University College London.
Much research has focused on cells with densely populated mitochondria, including those in human embryos and the eye. A new clinical trial sponsored by Columbia University in New York, will test whether brief exposure to red light can improve the quality of embryos produced during in vitro fertilization. Jeffery’s lab studies retinal aging, in which functional decline correlates with mitochondrial deterioration. Work from his group and others suggests that photobiomodulation could help protect retinal health. Work by Jeffery’s team even suggested that light might not need to be delivered directly to the eyes to have an effect.
In previous research, his group found that 15 minutes of red light exposure on the back blunted blood sugar spikes after a meal. Jeffery speculates that mitochondria could communicate with each other and “behave as a community throughout the body.”
Such discoveries have sparked not only enthusiasm, but also debate. Juanita Anders, researcher photobiomodulation at the Uniformed Services University in Bethesda, Maryland, who spoke independently of its government role, questions this assumption and says that larger, more carefully controlled studies are needed to determine potential distal or systemic impacts. One hypothetical pathway involves biophotons, or faint light produced by the cells themselves. Mitochondria are a major source of these particles and could use them to signal cellular health, Mitrofanis says. He co-authored a 2025 study that found that photobiomodulation altered biophoton production, particularly in stressed cells.
A trend could emerge: when cells are healthy, external light often has little effect. But in cases of disease or metabolic stress, in which mitochondrial dysfunction is common, its impact appears to be stronger. This distinction could help explain why results vary across studies.
Yet mitochondria probably don’t tell the whole story. “Even if you use a mitochondrial inhibitor, we still see a therapeutic response,” says Praveen Arany, a dentist and oral biologist at the University at Buffalo in New York, who studies the effects of red light.
The dosage seems crucial. Many researchers point out that there is a biological “golden mean” between too little and too much light. Others argue that wavelengths should not be considered in isolation, emphasizing the importance of a broad spectrum of light – as nature delivers it. “I like to think about light relationships,” says Elke Buschbeck, an evolutionary biologist at the University of Cincinnati in Ohio.
The light we no longer see
Humans evolved under sunlight, a spectrum that extends from about 300 to 2,500 nanometers. For most of human history, indoor lighting had similar characteristics. Today, as scientists discover the biological effects produced by red and near-infrared light, buildings have largely removed these wavelengths from the spaces where people spend about 90 percent of their time.
Modern window coverings filter out many of the longer wavelengths of sunlight to reduce the amount of heat entering buildings. Energy-efficient fluorescent fixtures and LEDs concentrate their power in a relatively narrow part of the visible spectrum. They are rapidly replacing incandescent bulbs, whose light filaments produced a much wider range of wavelengths. In fact, about 90% of an incandescent bulb’s energy is emitted as infrared radiation. The next updates to U.S. building and lighting standards, scheduled for 2028, are ex The spectrum of light available indoors is expected to be even more restricted.
Some scientists have raised the possibility that long-term deprivation of these and other wavelengths lost internally may subtly affect health. Human tissues can respond to light in ways that go beyond vision – through photoreceptor signaling in the eye that regulates circadian rhythms, mood, alertness and other functions, as well as through light-sensitive metabolic processes in cells. This has sparked calls for the restoration of wider spectrum electric lighting and better access to natural light in buildings, while again encouraging people to spend more time outdoors.
According to Buschbeck, just one minute outside in the sun provides her with as many visible photons as she would receive in about three hours in her office. “And if we included infrared, the difference would be even more dramatic,” she says.
Over the past two decades, studies have linked better access to natural light to better academic performance and shorter hospital stays. A study published this year in a controlled office-like environment suggests that daylight and near-infrared-enriched artificial light can improve markers of physiological and psychological health, including mood, heart rate variability, and glucose regulation. A preprint published in January, based on data from more than 400,000 adults, found that higher average sun exposure was associated with longer life expectancy, after accounting for skin cancer.
The questions are multiplying: could light be used not only to treat disease, but also to prevent it?
A better future
More than 150 years ago, Florence Nightingale, one of the founders of modern nursing, insisted that full-spectrum light was essential for recovery. “People think that the effect is only on minds,” she wrote in 1859. “This is by no means the case. »
Researchers are returning to this idea while trying to distance the field of photobiomodulation from the commercial frenzy that surrounds it. The wellness industry has rushed forward with little regulation, and scientists fear the trend is obscuring legitimate science. Consumers can now purchase red light wands, masks, helmets, signs, full mats and even units that look like tanning beds. Devices often come with bold promises that rely on weak data. “They give us a bad name,” Jeffery says. “There are all these companies saying, ‘You’ll live forever,’ and people like us saying, ‘This is a very important and interesting area of science.'”
Scientists who have begun testing commercial products are finding that while some are beneficial, they often do not live up to their claims. Many fail to administer a therapeutic dose. More independent testing – and clearer standards – are needed, says Anders. “There are people who do things right,” she says. “And if we can get the dosage right, it could be a real game-changer.” »
Looking ahead, researchers are exploring wearable or implantable LED devices combined with artificial intelligence algorithms to optimize processing in real time. NASA is studying near-infrared light therapy to support mitochondrial function during spaceflight. At the same time, others argue that the most consequential changes could be much less high-tech: rethinking lighting in the spaces where most people spend their lives.
Jeffery and Fosbury supplement their home’s lighting with a few incandescent bulbs, and they’re not the only ones experimenting on themselves. Ozog began using red light panels himself during his son’s recovery and says he quickly noticed the benefits: fewer cold sores, faster healing of wounds after abdominal surgery, clearer vision and reduced ADHD symptoms. Mitrofanis wears an LED-lined helmet daily as a hopeful preventative measure. And Anders is testing an anti-red light mask that has been independently tested. Buschbeck, however, remains cautious.
“It makes me nervous. We still don’t really understand what we’re doing,” she says. For those looking to improve their daily light diet, his advice is simple: get outside.
This article is reproduced with permission and has been published for the first time on March 25, 2026.
