Research explores red light therapy mostly for skin, exercise and hair, plus its safety and how light acts on cells. Many trials are small and use devices unlike home panels, so check each one's set-up and dose. At home, use a panel 8–50 cm from the skin for 10–30 minutes, at most 30 minutes a day on the same area.
How should you read a red light therapy study?
Start with the design. A randomised controlled trial (RCT) compares a group that gets light with a control group, ideally one given a sham light so nobody knows who got which. A systematic review collects many trials and weighs their quality; a meta-analysis also pools their numbers. Cell and animal studies help explain how light acts, but say little about people.
Then look at the dose: wavelength, irradiance (light power per area), session time, distance and the number of sessions. The two papers below show why these details matter. For home routines, see how often to use red light therapy.
Finally, check the device. Many trials used laser probes, LED clusters held on the skin, or helmets, not a panel used from a distance. Our Smart Small and Smart Medium panels measure 132 and 141 mW/cm² at 15 cm (spectrometer-measured), so a study's settings can't be copied one to one. They are made by a partner manufacturer to RedLightMed's specification and European (CE) requirements, and every unit is checked in Hungary.
The dark art of light measurement: accurate radiometry for low-level light therapy (Hadis MA et al., Lasers Med Sci, 2016). Of 74 light therapy papers published in 2014–2015, 73% gave no information on how the light was measured and relied on manufacturer-stated values.
Biphasic dose response in low level light therapy (Huang YY et al., Dose Response, 2009). This review describes a biphasic dose response, in which low levels of light often had a better effect than higher levels, and notes that the many possible settings have produced negative as well as positive studies.
What has research on skin looked at?
Skin is one of the most studied areas for LED light, partly because wrinkles, roughness and collagen density can be measured. The two trials below report changes in their participants; the review shows how strong the skin evidence is overall. How people fit red light into a skincare routine is covered in what red light therapy does and how to use it.
A prospective, randomized, placebo-controlled, double-blinded, and split-face clinical study on LED phototherapy for skin rejuvenation … (Lee SY et al., J Photochem Photobiol B, 2007). 76 adults with facial wrinkles had 830 nm, 633 nm, both or a sham light on half of the face twice a week for four weeks; over the study and a three-month follow-up, the light groups showed wrinkle reductions of up to 36% and elasticity gains of up to 19% against their starting values.
A controlled trial to determine the efficacy of red and near-infrared light … (Wunsch A, Matuschka K, Photomed Laser Surg, 2014). 113 of 136 volunteers received red (611–650 nm) or broadband (570–850 nm) light; after 30 sessions the light groups showed better complexion, lower skin roughness and higher collagen density, and blinded photo ratings favoured them over 23 controls without light.
Light-emitting diodes in dermatology: a systematic review of randomized controlled trials (Jagdeo J et al., Lasers Surg Med, 2018). This review of 31 RCTs of LED light on the skin rated none of the uses at the top grade of recommendation (the best received B, the rest C or D) and points to small samples of fewer than 20, missing blinding or sham groups, and varied settings.
What do studies on exercise and recovery measure?
Sports research measures performance, such as repetitions, time to exhaustion and maximum strength, and blood markers of muscle damage from exercise, such as creatine kinase. Most trials placed laser or LED probes directly on the muscle. For how these results fit with the limits of the evidence, see does red light therapy work.
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 (Leal-Junior EC et al., Lasers Med Sci, 2015). Of 13 RCTs of acceptable quality, 12 applied light before exercise; compared with placebo, repetitions rose by 5.47 and time to exhaustion by 4.12 seconds, while the creatine kinase results varied too much to pool (13 of 16 comparisons were positive).
What is the best moment to apply phototherapy when associated to a strength training program? A randomized, double-blinded, placebo-controlled trial (Vanin AA et al., Lasers Med Sci, 2016). 48 men in a 12-week strength programme received light and/or placebo before and/or after each session; the group with light before and placebo after showed the largest gains in the leg extension and leg press strength tests.
Photobiomodulation in human muscle tissue: an advantage in sports performance? (Ferraresi C, Huang YY, Hamblin MR, J Biophotonics, 2016). This review of 46 studies with 1,045 trained, untrained and elite participants sorts the light settings used before or after exercise into those with and without effects on performance and recovery.
What has hair research looked at?
Hair studies mostly test caps or helmets that hold lasers or LEDs close to the scalp, and count hairs in a marked patch of skin. These devices sit much closer than a panel and light only the scalp.
The growth of human scalp hair mediated by visible red light laser and LED sources in males (Lanzafame RJ et al., Lasers Surg Med, 2013). 44 men with androgenetic alopecia (hereditary hair thinning) used a helmet with 655 nm lasers and LEDs, or an identical-looking placebo, every other day for 16 weeks at home; of the 41 who finished, hair counts in the light group rose by about 39 percentage points more than with placebo, and no side effects were reported.
Photobiomodulation therapy with different wavebands for hair loss: a systematic review and meta-analysis (Zhang Y et al., Dermatol Surg, 2022). This meta-analysis of 36 studies with 966 participants analysed ultraviolet, red and infrared light separately; every analysis favoured light over control, while the authors note that earlier reported effects had been inconsistent.
What does research say about safety and the eyes?
Safety research looks at side effects on the skin and at how much light the eye can take. Our article on whether red light therapy is safe for the eyes explains the eye studies in more detail.
Safety of light emitting diode-red light on human skin: two randomized controlled trials (Jagdeo J et al., J Biophotonics, 2020). In two dose-escalation RCTs with 60 and 55 healthy adults, participants received red LED light or a mock light on the forearm three times a week for three weeks; no serious adverse events occurred, 3 participants had blistering or long-lasting redness at high doses, and darker skin was more sensitive to light.
Red light instruments for myopia exceed safety limits (Ostrin LA, Schill AW, Ophthalmic Physiol Opt, 2024). Two low-power red laser devices made for children to look into for myopia control were measured; 3 minutes of continuous viewing approached or exceeded the safe exposure limit for the retina.
Close your eyes or wear the goggles; there's a pair in every box.
It isn't recommended for children under 12, while breastfeeding, with epilepsy, with known tumours or metastases, or if you're sensitive to light. During pregnancy, only after talking to your doctor.
How do researchers explain the effect of light on cells?
The mechanism is still debated: reviews describe hypotheses, not settled facts. Our article on how red light therapy works explains them step by step.
Mechanisms and mitochondrial redox signaling in photobiomodulation (Hamblin MR, Photochem Photobiol, 2018). This review names cytochrome c oxidase in the mitochondria as the main site where red and near-infrared light is absorbed, with the hypothesis that light releases nitric oxide bound to it, and notes that healthy and stressed cells can respond in apparently opposite ways.
What lies at the heart of photobiomodulation: light, cytochrome c oxidase, and nitric oxide – review of the evidence (Quirk BJ, Whelan HT, Photobiomodul Photomed Laser Surg, 2020). This review finds no reliable demonstration of a light effect on cytochrome c oxidase and proposes the release of nitric oxide as the core of the effect.
Effect of wavelength and beam width on penetration in light-tissue interaction using computational methods (Ash C et al., Lasers Med Sci, 2017). In a computer model of multi-layered skin covering 300–750 nm, penetration depth increased with wavelength; about 1% of 750 nm light reached ≈5.4 mm. Longer near-infrared wavelengths were not modelled.
