The Science of Red Light Therapy
If you're curious about red light therapy and wondering what the research actually shows, you're in the right place. Scientists call it photobiomodulation, and it has been studied in hundreds of human trials — so we gathered ten of them here, in plain language.
No jargon and no hype. Just what researchers looked at, what they found, and a link to each study so you can read it yourself if you'd like.
On this page
First, how does it actually work?
It starts inside your cells. Your mitochondria are the tiny structures that turn oxygen and nutrients into usable energy, and researchers believe red and near-infrared light is absorbed by a specific enzyme in that energy chain called cytochrome c oxidase.
The leading theory is that light nudges a molecule out of the way that was slowing that enzyme down — a bit like clearing a blockage in a pipe. Once it clears, cells can go back to producing energy more efficiently, which may help explain the wide range of effects researchers see across skin, muscle, and joint studies (de Freitas & Hamblin, 2016).
Red vs. near-infrared: what reaches how deep
This is the single most useful thing to understand before choosing a device. Red light and near-infrared light do different jobs because they travel to different depths in your body.
Red light works closest to the surface, which is why skin and collagen studies use it. Near-infrared is invisible to your eye but passes deeper, which is why muscle recovery and joint studies rely on it. Hooga panels combine both, so one session covers the full range.
There's one more detail worth knowing: the gap between those two ranges — roughly 700 to 780 nm — is comparatively ineffective, which is why quality devices cluster their LEDs around specific wavelengths rather than spreading across the spectrum. You can see the exact wavelengths in each device on our Learn page.
What researchers have found
Here's what ten peer-reviewed studies found, grouped by area. Each one links to the full paper if you'd like to dig in.
Smoother skin and firmer collagen
Red light increased the density of collagen beneath the skin and left skin measurably smoother. Fine lines and wrinkles looked visibly improved in roughly 7 out of 10 people who used it.
Wunsch & Matuschka, 2014, Photomedicine and Laser Surgery — read the study
Helping stubborn wounds heal
Adding red and near-infrared light to standard wound care roughly doubled how often slow-healing wounds closed completely, and they tended to close faster.
Huang et al., 2021, International Wound Journal — read the study
Less soreness after a hard workout
People who used red or near-infrared light after tough training reported noticeably less muscle soreness two to four days later, and held onto more of their strength in the first day or two. Most studies found a benefit, though not every one did.
Tsou, Chang & Chang, 2025, Journal of Functional Morphology and Kinesiology — read the study
Easing knee pain and stiffness
Light therapy reduced knee pain more than a placebo and improved how well people moved and functioned. Relief often kept building for two to four weeks after the sessions ended rather than fading right away, and no side effects were reported.
Stausholm et al., 2019, BMJ Open — read the study
Thicker hair in early thinning
At-home red light devices produced consistent gains in hair density over four to six months in people with early pattern thinning — one study counted about 20 additional hairs per square centimeter. Results were similar for men and women.
Lueangarun et al., 2021, Journal of Clinical and Aesthetic Dermatology — read the study
Better sleep in a small athlete study
Red light was linked to better sleep quality, along with a near doubling of melatonin — the hormone that signals your body it's time to wind down. The people whose melatonin rose the most also reported the biggest sleep improvement. This is an early finding.
Zhao et al., 2012, Journal of Athletic Training — read the study
An early look at mood and near-infrared light
Near-infrared light to the forehead was linked to a larger improvement in mood scores than an inactive device. It's a promising early result that researchers are still following up on.
Cassano et al., 2018, Photomedicine and Laser Surgery — read the study
Relief from neck pain that lasted
People who received light therapy were significantly more likely to see their neck pain improve, and that relief held up at follow-ups as far out as 22 weeks. Side effects were mild and no more common than with a placebo.
Chow et al., 2009, The Lancet — read the study
Sharper attention in an older-adult study
Near-infrared light to the forehead was linked to better scores on a standard memory screening test, along with faster and more accurate responses on attention tasks. This is an early finding.
Papi et al., 2022, Przegląd Menopauzalny — read the study
Why session length and distance matter
Cells responded well to modest amounts of light and did worse when the amount was cranked up — the benefit rises, then falls off. The practical takeaway: consistency at the recommended distance and duration beats longer, closer sessions.
de Freitas & Hamblin, 2016, IEEE Journal of Selected Topics in Quantum Electronics — read the study
So how long until I see results?
This is the question we get most, and the studies above give a reasonable answer: it depends on the tissue. Fast-turnover things like muscle soreness respond within days. Skin and hair rebuild slowly, so those take months. Here's roughly what the research timelines looked like.
| Goal | When studies saw change | Session pattern used |
|---|---|---|
| Muscle soreness | Within 1–4 days of a hard session | Applied after training |
| Joint comfort | Around 3–4 weeks, often still improving 2–4 weeks after finishing | 8–12 sessions |
| Sleep quality | About 2 weeks | Nightly |
| Skin & collagen | About 12 weeks | 2× per week |
| Hair density | 16–26 weeks | 3× per week or every other day |
The pattern across all of them is consistency. Most of these studies ran several sessions a week for weeks or months, and very few showed overnight changes. Results also vary from person to person — even in the positive studies, not every participant responded.
Why the dose matters
The research is clear that there's a sweet spot: too little light does nothing, and too much can work against you. That makes irradiance — how much light energy actually reaches you — the number that matters most, and it drops off quickly as you move away from a panel.
What this means in practice. Follow the distance and session length in your manual instead of getting closer or going longer to speed things up. The studies that used well-chosen doses clearly outperformed the ones that didn't — and in lab research, piling on more light reversed the benefit.
Studies referenced on this page
- Wunsch A, Matuschka K. Red and near-infrared light treatment for fine lines, wrinkles, skin roughness, and intradermal collagen density. Photomed Laser Surg. 2014. PMC3926176
- Huang J, et al. The effect of low-level laser therapy on diabetic foot ulcers: a meta-analysis of randomised controlled trials. Int Wound J. 2021. PMC8613395
- Tsou YA, Chang NJ, Chang WD. Photomodulation therapy for delayed onset muscle soreness: a systematic review and meta-analysis. J Funct Morphol Kinesiol. 2025. PMC12286287
- Stausholm MB, et al. Efficacy of low-level laser therapy on pain and disability in knee osteoarthritis. BMJ Open. 2019. PMC6830679
- Lueangarun S, et al. Home-use, low-level light/laser therapy devices for pattern hair loss: a systematic review and meta-analysis. J Clin Aesthet Dermatol. 2021. PMC8675345
- Zhao J, et al. Red light and the sleep quality and endurance performance of Chinese female basketball players. J Athl Train. 2012. PMC3499892
- Cassano P, et al. Transcranial photobiomodulation for major depressive disorder: the ELATED-2 pilot trial. Photomed Laser Surg. 2018. PMC7864111
- Chow RT, et al. Efficacy of low-level laser therapy in the management of neck pain: a systematic review and meta-analysis. Lancet. 2009. PMID 19913903
- Papi S, et al. Transcranial photobiomodulation and cognitive function in older women with mild cognitive impairment. Prz Menopauzalny. 2022. PMC9551363
- de Freitas LF, Hamblin MR. Proposed mechanisms of photobiomodulation or low-level light therapy. IEEE J Sel Top Quantum Electron. 2016. PMC5215870
- Quirk BJ, Whelan HT. What lies at the heart of photobiomodulation: light, cytochrome c oxidase, and nitric oxide. Photobiomodul Photomed Laser Surg. 2020. PMC7495914
Reviewed by the Hooga Product Team. Last updated September 3, 2026. Each study above links to its public listing in PubMed or PubMed Central. This page is provided for education and does not constitute medical advice.