Does red light therapy work? The evidence for skin, hair, muscles, joints and aging

What the evidence shows, use by use

Two meta-analyses found higher hair density with laser and LED hair devices in pattern hair loss^{8, 9}. But Cochrane rated the hair-count evidence low quality, and women using laser combs didn’t rate their hair as improved more often than sham users¹⁰.

In placebo-controlled trials, lasers aimed at the knee lowered osteoarthritis pain by about 14 points out of 100¹³. Trials that used recommended doses saw about 19 points of relief¹³. Results varied widely between trials, though, and major osteoarthritis guidelines don’t recommend laser therapy¹³. After the evidence for each use, this review covers dose, what FDA clearance means, safety and what to check before you buy.

Pattern hair loss has the largest body of pooled studies. A 2025 meta-analysis included 38 studies with 3,098 patients, 2,930 of them with androgenetic alopecia⁹. In androgenetic alopecia, hair density rose more with low-level laser or LED therapy than with placebo⁹. For treatment shorter than 20 weeks, the standardized mean difference was 1.14 (95% CI 0.51 to 1.78)⁹. For longer treatment it was 1.44 (95% CI 0.97 to 1.91)⁹. The studies disagreed a lot about how big the effect was, with heterogeneity (I²) of 88% and 81%⁹.

A 2019 meta-analysis of 11 double-blind trials from eight studies compared laser devices with sham devices⁸. It also found higher hair density with the laser (standardized mean difference 1.32, 95% CI 0.99 to 1.64)⁸. It reported increased hair growth in both men and women, and with both comb-type and helmet-type devices⁸. Its authors said heterogeneity among the trials limited the review⁸.

The Cochrane review of female pattern hair loss is more cautious. Two trials with 141 women compared laser combs with sham devices¹⁰. In each trial, total hair count rose by about 17 more with the laser comb, but Cochrane rated that evidence low quality¹⁰. Women weren’t more likely than sham users to rate their hair as improved (moderate-quality evidence)¹⁰. The authors called the results for laser devices inconsistent¹⁰.

For knee osteoarthritis, there’s a 2019 meta-analysis of 22 placebo-controlled trials with 1,063 participants (mean age about 60)¹³. At the end of treatment, low-level laser therapy reduced pain by 14 points on a 0 to 100 scale compared with placebo (95% CI 7 to 21)¹³. Trials that used the doses recommended by the World Association for Laser Therapy saw about 19 points of relief¹³. Disability also improved, and no trial reported an adverse event¹³. Results varied widely between trials, though (I² 93% for the main pain analysis)¹³. These were lasers applied to treatment spots on the knee at set doses per spot, not whole-body panels¹³.

For exercise, a 2023 systematic review found 15 randomized trials with 428 participants¹¹. Trial sizes ranged from 6 to 96 people¹¹. Most reported better maximal strength, oxygen uptake or time to exhaustion, and lower creatine kinase, a marker of muscle damage¹¹. Results were better when the light was applied before exercise¹¹. The trials varied too much in laser settings and muscles treated to be pooled in a meta-analysis¹¹.

A 2024 meta-analysis looked at injured athletes: six randomized trials with 205 competitive and recreational athletes¹². Pain was lower with photobiomodulation than with the control treatments (standardized mean difference 1.03, 95% CI 0.43 to 1.63)¹². The controls were placebo light in four trials, standard physical therapy in one and aloe gel in one¹². But the two trials that measured time to return to play didn’t support a benefit¹².

For skin, a 2018 systematic review covered 31 randomized trials of LED treatment⁶. It gave a grade B recommendation only to acne, herpes simplex and zoster, and acute wound healing⁶. Every other skin condition it reviewed got a weaker grade C or D⁶. Skin rejuvenation, the closest match to wrinkle claims, got grade C, based on six trials with 23 to 112 participants each⁶. The authors flagged limitations in some of the studies: small samples (fewer than 20 people), missing blinding, no sham control and varied treatment settings⁶.

The Cochrane review of light therapies for acne included 71 trials with 4,211 people⁷. It covered light alone and light combined with a drug applied to the skin⁷. Most trials were small (median 31 participants), and the authors couldn’t draw firm conclusions⁷.

What the evidence does not show

It doesn’t show that red light slows aging. The reviews above measured outcomes such as hair density, pain, strength, fatigue and acne lesion counts^{7–9, 11, 13}. None of them measured lifespan, biological age or the risk of age-related disease. And none of the sources cited here reports a trial in people that did.

It doesn’t show that any given home panel or mask works. The knee results came from lasers delivering a set number of joules to defined treatment spots¹³. The review’s authors concluded that laser therapy reduced pain and disability at 4 to 8 joules per spot with 785 to 860 nm lasers¹³. With 904 nm lasers, the range was 1 to 3 joules per spot¹³. Major osteoarthritis guidelines also don’t recommend laser therapy, a point the knee review’s authors raise themselves¹³.

It doesn’t show that people will notice a difference. In the Cochrane review, hair counts rose with laser combs¹⁰. Yet women using them didn’t rate their hair as improved more often than women using sham combs¹⁰. In injured athletes, pain fell, but the trials that measured return to play didn’t support a faster return¹².

It doesn’t settle acne either. The Cochrane acne review concluded that high-quality evidence on light therapies for acne is lacking⁷. The comparison it rated moderate quality pitted photodynamic therapy (red light plus a light-activated drug applied to the skin) against red light with a placebo cream⁷. In three trials with 360 people with moderate to severe acne, there was little or no difference in lesion counts⁷. The authors had low certainty that photodynamic therapy is useful as a standard treatment for moderate to severe acne⁷.

Finally, the exercise evidence rests on small, varied trials. The 2023 review’s trials ranged from 6 to 96 participants¹¹. They spanned wavelengths from 640 to 905 nm and energy doses from 5 to 480 joules¹¹. So there’s no single protocol a consumer device can claim to copy.

Dose, irradiance and wavelength

A light dose has three parts: the wavelength, the irradiance reaching the skin and the time. Irradiance is power per area, usually given in mW/cm². Multiply it by the seconds of exposure and divide by 1,000 to get the energy density in J/cm². Trials report dose this way, or in joules per treatment spot.

The knee osteoarthritis meta-analysis found that dose mattered¹³. At the end of treatment, trials that used the recommended doses showed about 19 points of pain relief out of 100¹³. That compares with 14 points across all trials, and about 6 points in trials that didn’t use the recommended doses¹³.

The muscle trials used wavelengths from 640 to 905 nm¹¹. In the knee review, trials that met the recommended doses used 785 to 860 nm or 904 nm lasers¹³. FDA’s infrared lamp regulation describes devices that emit infrared energy from roughly 700 to 50,000 nm to provide topical heating⁵.

Irradiance falls with distance from a panel. So a figure means little unless the distance and the measuring instrument are stated. Without them, you can’t compare two irradiance claims or match either one to a trial dose.

Does FDA clearance mean it works?

A 510(k) is a premarket submission showing that a new device is as safe and effective as one already legally sold¹. FDA’s order “clears” the device for sale¹. Premarket approval (PMA) is a separate route¹. Clearance rests on comparison with that earlier device. The new one must have the same intended use, and any technical differences must not raise different questions of safety and effectiveness¹. That isn’t the same as a trial showing the device delivers a meaningful benefit.

Light devices sold for wrinkles or hair growth go through this route. Over-the-counter wrinkle devices sit in FDA product code OHS, and laser hair combs in product code OAP^{2, 3}. Both are Class II categories that call for a 510(k)^{2, 3}. Clearance is also tied to a specific use: the OAP category describes promoting hair growth in men with androgenetic alopecia at Norwood-Hamilton stages IIa to V³. A device cleared for hair growth or wrinkles hasn’t been cleared for recovery, fat loss or aging.

Infrared therapeutic heating lamps (product code ILY) are a separate category⁴. FDA classifies them as Class II but exempts them from premarket notification, so a 510(k) generally isn’t required^{4, 5}. The exemption is subject to the limitations in 21 CFR 890.9^{4, 5}. Before you rely on any “FDA cleared” claim, ask for the 510(k) number and read the indication in FDA’s database.

Is red light therapy safe? Eyes, medicines and skin

The reviews reported few side effects, but reporting was often thin. No trial in the knee osteoarthritis meta-analysis reported an adverse event, and the 2018 LED review described few^{6, 13}. Where LED trials did report side effects, they included dryness, redness, a burning sensation, swelling, pigment changes and, in one trial, eye symptoms⁶. Acne trials did report blistering with intense pulsed light, infrared light and photodynamic therapy⁷. But most acne trials reported side effects poorly, and the evidence on side effects was rated very low quality⁷.

Eye exposure is a concern with face masks and bright panels. In 2019 Neutrogena recalled its red and blue Light Therapy Acne Mask, saying it acted out of an abundance of caution¹⁴. It cited a theoretical risk of eye injury for a small subset of people with certain underlying eye conditions¹⁴. It named the same risk for users taking medications that could increase the eye’s sensitivity to light¹⁴. The company said reports of visual effects were rare and generally mild and transient¹⁴.

Medicines that increase sensitivity to light are the other flag. The recall named them specifically as a risk to the eyes¹⁴. If you take such a medicine or have an eye condition, read the device warnings and ask a clinician before use.

• Wear the eye protection supplied and follow the device’s instructions about looking at the LEDs
• Neutrogena told users of the recalled mask who had visual discomfort to stop and contact a healthcare professional¹⁴
• Stick to the session length and distance in the device’s instructions
• The knee trials that reported no adverse events used lasers at defined doses on the knee, so they say little about longer or closer sessions with a home panel¹³

What to look for when buying a panel or mask

The benefit depends on dose, and device claims are hard to verify. In the knee review, trials that met the recommended per-spot doses showed larger effects than trials that did not¹³. So buy on documentation rather than on LED counts or wavelength lists. These checks help you compare devices, but they won’t predict your own result.

• Verified irradiance in mW/cm² at your actual distance, with the meter named, since a figure “at the surface” or with no distance can’t be compared or turned into a dose
• A dose you can calculate (irradiance times session length gives J/cm²), not just an advertised maximum power
• The exact FDA status: a 510(k) number whose indication matches your use, or a plain statement that the device is an exempt infrared heating lamp^{1, 4}
• EMF and flicker claims backed by a test report: treat “zero EMF” and “flicker-free” as marketing unless the seller publishes the method, the instrument and the distance used
• Eye protection in the box, plus clear instructions on eye safety and photosensitizing medicines¹⁴
• Warranty and returns: how long the warranty runs, whether LED failure is covered, who pays return shipping and how long the return window is

Sources

1. Premarket Notification 510(k) US Food and Drug Administration, 2024 · regulator
2. Product classification: light based over the counter wrinkle reduction (product code OHS) US Food and Drug Administration · regulator
3. Product classification: laser, comb, hair (product code OAP) US Food and Drug Administration · regulator
4. Product classification: lamp, infrared, therapeutic heating (product code ILY) US Food and Drug Administration · regulator
5. 21 CFR 890.5500 Infrared lamp Electronic Code of Federal Regulations, 2019 · regulator
6. Light-emitting diodes in dermatology: a systematic review of randomized controlled trials Lasers in Surgery and Medicine, 2018 · systematic review
7. Light therapies for acne Cochrane Database of Systematic Reviews, 2016 · systematic review
8. Comparative effectiveness of low-level laser therapy for adult androgenic alopecia: a system review and meta-analysis of randomized controlled trials Lasers in Medical Science, 2019 · meta-analysis
9. Low-level laser and LED therapy in alopecia: a systematic review and meta-analysis Dermatologic Surgery, 2025 · meta-analysis
10. Interventions for female pattern hair loss Cochrane Database of Systematic Reviews, 2016 · systematic review
11. Does photobiomodulation improve muscle performance and recovery? A systematic review Revista Brasileira de Medicina do Esporte, 2023 · systematic review
12. Effects of photobiomodulation on pain and return to play of injured athletes: a systematic review and meta-analysis Journal of Strength and Conditioning Research, 2024 · meta-analysis
13. Efficacy of low-level laser therapy on pain and disability in knee osteoarthritis: systematic review and meta-analysis of randomised placebo-controlled trials BMJ Open, 2019 · meta-analysis
14. Neutrogena recalls light therapy masks for risk of eye damage ABC11, 2019 · news