Science · Health
Red light: what it really does, and what is just marketing
Light therapy is in fashion and the lamps sell themselves. The evidence says it works for a few very specific things, and barely at all for almost everything else.
Search for “red light” and you will find everything: that it rejuvenates the skin, that it burns fat, that you will sleep better, that it gives you energy, that it cures almost anything. Behind all that sits a real technique with a serious name (photobiomodulation) and dozens of devices on sale. The useful question is not whether it “works”, but what it works for and what it doesn’t.
Photobiomodulation uses red light (around 630-700 nanometres) and near infrared (around 780-1,100 nanometres), delivered by LED or low-level laser. It has solid clinical evidence for a few specific uses, and very little for almost everything the advertising promises. Here we separate one from the other, selling nothing.
Where the evidence is real
Recent clinical reviews back it most strongly in two uses: the healing of wounds and ulcers, and mucositis (the mouth sores caused by chemotherapy and radiotherapy), which is probably its best-documented indication. In acne and skin rejuvenation the results are promising, with a caveat that is almost never mentioned: the reference trial (Goldberg and Russell, 2006, twenty-four patients) did not test red light on its own, but blue light at 415 nanometres alternated with red at 633. Since photobiomodulation is defined by red and near infrared, that result cannot be credited to it in full. The evidence is patchier and the protocols less standardised, so it should not be sold as settled. There is also reasonable support in hair loss and positive results in some trials on joint and muscle pain, where the evidence is clearly more limited.
Where it is oversold
The jump from “it works on skin” to “it works on everything” is pure marketing. The generic wellness uses (burning fat, “detox”, energy) have no solid backing, though the bag is worth separating out: in 2010 the US Food and Drug Administration authorised a low-level laser for body contouring through the De Novo route, so “no evidence at all” would be false. That said, a marketing authorisation is not proof of efficacy, and for “detox” and “energy” there is neither one nor the other. And be wary of the round numbers that circulate on the blogs selling lamps (“cuts inflammation by 38%”, “three times better than placebo”): they are poorly supported, and some of them put words into prestigious journals that those journals never said.
Does it work? Level of evidence, use by use
Degree of clinical evidence for photobiomodulation (red light / near infrared), use by use.
| Use | Evidence | Type of light | Note |
|---|---|---|---|
| Healing of wounds and ulcers | Solid | Red/NIR | LED or low-level laser |
| Mucositis (chemotherapy/radiotherapy) | Solid | Red/NIR | One of its best-supported uses |
| Acne and skin rejuvenation | Moderate | Blue 415nm + red 633nm, combined | The reference trial alternates the two colours; it is not red light on its own |
| Hair loss (alopecia) | Moderate | Red/NIR | Positive results, less consistent |
| Joint and muscle pain | Limited | NIR 780-1,100nm | Positive in some trials |
| “Fat burning” / detox / energy | Very limited | Low-level laser | The FDA authorised a body-contouring device in 2010; “detox” and “energy” have no backing |
| Night-time light for sleeping | Solid (different use) | Red/amber, ambient | Not a clinical therapy |
Source: JAAD 2024 (CME review of photobiomodulation); IJMS/MDPI 2024. Two rows also rest on sources of their own: the acne row on Goldberg and Russell 2006 (PMID 16766484), which alternates blue at 415 nm and red at 633; the fat-burning row on the FDA De Novo file DEN090008, granted on 24 August 2010, which is a marketing authorisation and not proof of efficacy.
The use that does hold up: light at night
There is one use that never appears in the medical reviews of light therapy and that does, nonetheless, have solid backing: the light in your house at night. Our body clock is set by the light that reaches the eyes, and blue light (the light of screens and of many LED bulbs, peaking at around 460-480 nanometres) is the one that most suppresses melatonin, the hormone that prepares the body for sleep. Red or amber light barely touches it. So swapping the hard, bluish lights of the last hours of the day for a soft red lamp is not a treatment: it is, quite simply, not sabotaging your own rest. I swapped my own living-room lamp for one of these a while back, and the logic is the same: it cures nothing, it just stops getting in the way. Mind the distinction: this is ambient light, not a clinical dose or a “therapy” panel for the skin.
Melatonin suppression by colour of light
No figures: the percentages that were here had no source. What holds up is the order, not the size.
What separates one from the other
There is an enormous difference between a clinical use (a medical device, with a measured dose and measured parameters, applied to a specific indication) and a consumer gadget that promises everything and specifies nothing. If you are thinking of buying one, the question is not “does red light work?”, but “for my particular problem, and at what dose?”.
Red light is neither a scam nor a miracle: it is a tool with real, narrow uses that fashion has stretched to the absurd. Knowing what it is good for is also knowing what it isn’t.
Sources
- Journal of the American Academy of Dermatology (2024), CME review of photobiomodulation — primary/review.
- Review in IJMS (MDPI, 2024) — primary/review.
- Goldberg DJ, Russell BA, “Combination blue (415 nm) and red (633 nm) LED phototherapy in the treatment of mild to severe acne vulgaris”, J Cosmet Laser Ther 2006;8(2):71-75, PMID 16766484. Twenty-four patients. This is the trial behind the acne row, and it alternates the two colours.
- FDA, De Novo database, file DEN090008 (associated 510(k) number K082609): “fat reducing low level laser”, Erchonia ML Scanner, decision granted on 24 August 2010, regulation 878.5400. It is a marketing authorisation, not a demonstration of efficacy.
- Declared gap. Chart 2 (melatonin suppression by colour) has been withdrawn: its three percentages had no source and this list contains no work on circadian rhythm. Brainard 2001 and Thapan 2001, the canonical studies, publish no figures by colour and did not measure red or amber.
- A commercial reference page on red light lamps, used only as market context, with no promotional intent.