Light therapy is certainly having a moment. You can now buy glowing gadgets for everything from skin conditions and wrinkles to sore muscles and gum disease, the latest being a toothbrush enhanced with tiny red LEDs, described by its makers as “a breakthrough in at-home oral care”. Globally, the market was worth $1bn in 2024 and is projected to grow to $1.8bn by 2035. You can even go and sit in an infrared sauna, where instead of hot coals (real or electric) heating the air, your body is warmed directly by infrared light. According to its devotees, it’s like bathing in one of those LED-lit beauty masks, boosting skin collagen, relaxing muscles, relieving inflammation and chronic health conditions while protecting against dementia.
“It sounds a bit like witchcraft,” says Paul Chazot, professor in neuroscience at Durham University and a convert to the value of light therapy following 20 years of research in the field. Of course, some of light’s effects on our bodies are well established. Sunlight helps us make vitamin D, needed for bone health, immunity, muscles and more. Sunlight regulates our circadian rhythms, too, triggering the release of neurochemicals and hormones while we are awake, and winding down bodily functions for sleep as it fades into night. Sunlight-imitating lamps are a common remedy for people with seasonal affective disorder (Sad) to boost low mood in winter. So there’s no doubt we need light energy to function well.
While Sad lamps tend to use a mixture of light frequencies from the blue end of the spectrum, most other light therapy devices deploy red or infrared light. In serious clinical research, such as Chazot’s investigations into the effects of infrared on brain cells (more on which, later), finding the right frequency is key. Light is a form of electromagnetic radiation, which runs the spectrum from the lowest-energy, longest wavelengths (radio waves) to the highest-energy (gamma waves). Phototherapy, or light therapy, uses wavelengths around the middle of this spectrum, the highest energy of those being invisible ultraviolet, then visible light (all the colours we see in a rainbow) and then infrared (which we can see with night-vision goggles).
UV light has been used by medical dermatologists for many years to treat chronic skin conditions such as eczema, psoriasis and vitiligo. It works on the immune system within cells, “and dampens down inflammation,” says Dr Bernard Ho at the British Association of Dermatologists. “There’s lots of evidence for phototherapy.” UVA goes deeper into the skin than UVB, whereas the LEDs we see on consumer light-therapy devices (which generally deliver red, infrared or blue light) “tend to be a bit more superficial”.
The side-effects of UVB exposure, such as burning or tanning, are well known but in medical devices the light is delivered in a “narrow-band” form – meaning smaller wavelengths – which minimises the risks. “It’s supervised by a healthcare professional, so the dosage is monitored,” says Ho. And crucially, the lightbulbs are calibrated by medical technicians, “to ensure that the wavelength that’s being delivered is fit for purpose – unlike in tanning salons, where it’s a bit unregulated, and we don’t really know what wavelengths are being used”.
Red and blue LEDs, he says, “aren’t really used in the medical sense, but they may help with certain conditions”. Red LEDs, it is proposed, help boost blood circulation, oxygen uptake and cell renewal in the skin, and stimulate collagen production – a key aspiration in anti-ageing effects. “The evidence is there,” says Ho. “Although it’s not strong.” In any case, amid the sea of devices now available, “we don’t know whether or not the lights emitted are reflective of the research that has been done. We don’t know the duration, how close the lights should be to the skin, whether or not that will increase the risk versus the benefit. There are lots of questions.”
One of the earliest blue-light products targeted Cutibacterium acnes, a microbe associated with acne. The evidence for its efficacy isn’t strong enough for it to be routinely prescribed by doctors – although, says Ho, “it’s often seen in medical spas or aesthetics practices”. Some of his patients use it as part of their routine, he says, but if they’re buying a device for home use, “we just tell them to try it carefully and to make sure it has been assessed for safety. Unless it’s a medical device, the regulation is a bit grey.”
Meanwhile, in a far-flung field of pioneering medical science, Chazot has been experimenting with brain cells, identifying a number of ways in which infrared can boost cellular health. “Pretty much everything I did with the light at that particular wavelength was positive and protective,” he says. It is partly these many and varied positive effects on cellular health that have driven scepticism about light therapy – that it’s too good to be true. But his research has thoroughly changed his mind in that respect.
Chazot mostly works on developing drug treatments for neurodegenerative diseases, but over 20 years ago, a GP who was developing an antiviral light treatment for cold sores sought his expertise as a biologist. “He created some devices so that we could work with them with cells and with fruit flies,” he says. “I was pretty sceptical. It was an unusual wavelength of about 1070 nanometres, that nobody believed did anything biological.”
What it did have going for it, though, was that it travelled through water easily, meaning it could penetrate the body more deeply.
More evidence was emerging at the time that infrared light targeted the mitochondria in cells. Mitochondria are the powerhouses of cells, generating energy for them to function. “Every cell in your body has mitochondria, including the brain,” says Chazot, who, as a neuroscientist, decided to focus the research on brain cells. “It has been shown that in humans this light therapy increases blood flow into the brain, which is always very good.”
With 1070 treatment, mitochondria also produce a small amount of a molecule known as reactive oxygen species. In low doses this substance, says Chazot, “stimulates so-called chaperone proteins which look after your mitochondria, look after your cells and also deal with the unwanted proteins”.
All of these mechanisms appear promising for treating a brain disease: antioxidant, anti-inflammatory, and pro-autophagy – autophagy being the process the cell uses to clear unwanted damaging proteins.
The last time Chazot checked the literature on using the 1070 wavelength on human dementia patients, he says, about 400 people were taking part in four studies, including his own initial clinical trials in the US.
Alzheimer’s Society describes research into light therapy as “promising”. However, it adds: “The research is still in its infancy and there is now not enough evidence to recommend using light therapy as an intervention in dementia.”
One area where professionals have largely ditched light therapy is physiotherapy, according to Lucy Macdonald, a physiotherapist working in Surrey. Not that this stops high-end gyms and consumer devices offering red-light and laser therapy to aid muscle recovery and reduce musculoskeletal aches and pains.
Special red and infrared lasers, it has been claimed, could cause micro-injuries deep into cartilage and help it regrow. “It was considered that lower frequency levels would penetrate deeper,” says Macdonald. “Even when I first qualified, about 25 years ago, it was still being used. But no one uses it now for deep tissues like cartilage. It can be helpful and is still used for superficial lesions, wound healing and that sort of thing, hence where you get the overlap with the beauty industry. But for deep applications, there’s no evidence to show that it works.”
The studies behind the claims that it can heal deep tissue are not randomised control trials, she says. “They’ll take two subject groups, and they’ll do a different type of laser on both of them, and then they’ll look at the outcomes of those two, but they’re not controlling it against no treatment. And obviously the body has an innate healing ability.”
A few decades ago, she recalls, “people would go to the physio, be strapped up to a machine, press the button and off you go”. The placebo effect should never be underestimated, she says: “During that laser session, you’ve been talking to a physio, the problem’s been validated. You’ve got reduced fear levels. You feel more nurtured, and you’re ready to then go and be more active and move more and all the things that we know actually do help with cartilage issues – but it’s not the laser. Because when they control for the laser, it’s not shown to be effective.”
She says that if she or anyone in her family had cartilage issues, she wouldn’t waft a laser over it. “Nowadays there’s so many other highly effective treatments with decent evidence.”
What about the full-body beds studded with red LEDs now available in swanky gyms, and the expensive body mats for sale online, promising to aid muscle recovery? Macdonald can’t find any clinical studies to support their claims. “The best thing people can do to aid muscle recovery,” she says, “is keep moving because this maintains good circulation, eat healthily so that you’ve got all the building blocks for repair, and sleep.” Healing peaks during sleep.
Similarly, Ho wouldn’t necessarily recommend LED products for the skin, although he suspects the risks are minimal if used as directed. “What overdoing it would probably mean is exerting too much heat on the skin, which can induce either pigmentation or even more inflammation in the skin. So there’s some concerns around the use of these products.”
But even Ho has been tempted to try one. “It is kind of fun to use. I used it for a bit of brightening, a bit of anti-pigmentation. Mine has different modes to it, but I have to remind myself that it’s not a medical treatment. I think if you go in with the mindset that it’s a splurge, a fun treat to yourself … but I would avoid overuse, and use as it’s directed.” If you can afford it, you may, he says, “in theory have some nice-looking effects, even if it’s short-lived. If it gives you a little boost, or if it makes you feel a bit better, why not? But don’t rely on it as a holy grail.”
In aesthetic dermatology practises, says Ho, LEDs are used to reduce some of the side-effects from other treatments that can cause inflammation, such as peels or injections. “The idea is the LED light will help reduce some of that downtime.” Professional or medical-grade equipment should have a CE marking, denoting higher standards of testing than with over-the-counter versions. Still, he says, “the evidence on exactly how much to use it, and at what frequency, is still slightly guesswork. Even if you’re using a medical device, it will depend on the device itself and what the manufacturers’ recommendations are based on their testing.” We also don’t know which, if any, beauty products might reduce or enhance their efficacy, and whether treatment should be before or after applying them.
The jury also remains out for the new red-light toothbrush, or the myriad other glowing devices you can buy to fix gum disease. The British Dental Association says this is such a young field its experts aren’t yet in a position to assist. As with so many other consumer light-therapy products, while they could theoretically help reduce inflammation and boost cellular health, in terms of their efficacy and safety we remain largely in the dark.
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