What it is
Red light therapy — photobiomodulation (PBM) or low-level laser therapy in the literature — exposes tissue to red (630–670 nm) and near-infrared (810–850 nm) light at an intensity too low to heat it. The light is absorbed mainly by cytochrome c oxidase in the mitochondria, which transiently increases ATP production, releases a small burst of nitric oxide and reactive oxygen species, and sets off a signalling cascade that, in the right dose, is reported to reduce inflammation and speed tissue repair.
Red wavelengths penetrate a few millimetres and are the skin wavelengths. Near-infrared penetrates deeper — muscle, tendon, joint capsule — and is the recovery wavelength. Most serious panels and clinic beds combine both. The source can be LED or laser; for whole-body or large-area use the difference matters less than the dose.
What the research says
| Use | Evidence grade | What was found |
|---|---|---|
| Muscle soreness and recovery after exercise | Moderate — multiple small RCTs, meta-analyses (Leal-Junior and others) | Lower creatine kinase, less soreness, slightly better repeated performance when light is applied before exercise. Effects are modest and the trials are small. |
| Skin — fine lines, collagen density, photo-ageing | Moderate — RCTs including a 136-person split-face trial (Wunsch & Matuschka 2014) | Improved skin roughness and measured collagen density after 30 sessions over 15 weeks. Real, but gradual. |
| Androgenetic hair loss | Moderate — several device RCTs; devices cleared by regulators for this use | Increased hair density versus sham over 16–26 weeks. Works best early in thinning. |
| Tendinopathy and joint pain | Moderate / mixed | Positive for some tendons and knee osteoarthritis pain at correct dose; many negative trials used doses too low to matter. |
| Sleep | Early — one small trial in athletes (Zhao 2012), mechanism via melatonin | Improved sleep quality scores and serum melatonin after 14 nights of whole-body red light. Not replicated in the general population. |
| Wound healing, oral mucositis | Strong for mucositis in cancer care; moderate for wounds | A clinical use with guideline backing, which is why clinics have the equipment at all. |
| Testosterone, fat loss, "cellular energy" | Hype | One rodent study, a few unblinded body-contouring trials with tiny changes, and marketing. |
Protocols that are studied
The dose is the whole game. Too little does nothing; too much reverses the benefit — the response is biphasic, and several negative trials simply overdosed.
- Wavelengths. Skin: 630–670 nm. Muscle, tendon, joint: 810–850 nm. Combination panels cover both; a device that lists only "red" with no number is a lamp.
- Irradiance. 20–100 mW/cm² at the skin. Panels quote a figure at zero distance; at 30 cm it is often a third of that. Ask for the measured value at the distance you will use.
- Dose. 3–10 J/cm² per area for skin and muscle in most positive trials; up to 30–60 J/cm² for deep joints with near-infrared. Dose = irradiance × seconds ÷ 1000, so at 50 mW/cm², ten minutes gives 30 J/cm² — more than the skin needs.
- Session time. 5–15 minutes per area is the usual range at clinic-grade intensity.
- Frequency. Skin: three to five times a week for 8–15 weeks. Recovery: before each hard session. Hair: three times a week for at least four months.
- Distance. 15–30 cm from a panel; direct contact for hand-held devices.
Who it suits — and who should avoid it
It suits anyone with a skin, hair or soreness target who can be consistent for weeks — the evidence is for repeated use, not one visit. It is one of the few therapies on this site with a sensible home version, provided the device publishes wavelength and measured irradiance.
- Photosensitising medicines — some antibiotics, retinoids, St John's wort, certain diuretics. Check with the prescriber.
- Active cancer in the treated area — the mitochondrial stimulus is non-selective; a precaution in every guideline.
- The eyes. Near-infrared is invisible and the blink reflex does not protect you. Goggles for face and whole-body sessions.
- Pregnancy over the abdomen, epilepsy with pulsed devices, open tattoos — relative; a physician conversation.
- Thyroid area — avoid direct near-infrared on the front of the neck without a reason.
Where it fits in a personal protocol
Two placements. In a skin protocol, red light runs alongside the compounds studied for collagen and repair: GHK-Cu on its own or inside the GLOW combination. The mechanisms are separate — copper-peptide signalling versus a mitochondrial light stimulus — so stacking is plausible, and coaches usually schedule the light on the same days, after the skin has been cleaned and before any topical.
In a training or recomposition protocol, near-infrared goes on the muscles about to be worked, 5–10 minutes before the session. This is the timing the positive trials used; applying it afterwards is less consistently helpful, and unlike cold it does not appear to blunt adaptation. The recomposition goal page shows where recovery levers sit in a twelve-week plan, and the cycle guide explains why they are front-loaded in the heavier blocks.
The hype vs the evidence
- "Boosts testosterone." One rat study with a bulb pointed at the testes. No human trial shows it; do not aim a panel there.
- "Melts fat." Body-contouring trials with 635 nm lasers report circumference changes of a centimetre or two, unblinded, with no change in weight. The fat is not going anywhere.
- "More power is better." The dose–response is biphasic. Bigger panels at closer range frequently push past the useful window.
- What is solid: skin texture and collagen with a 10–15-week course, hair density in early androgenetic thinning, less soreness when used before training, and mucositis in cancer care.
Frequently asked questions
Before or after training?
Before. The trials showing less soreness and better repeated performance applied near-infrared to the working muscles 5–10 minutes before exercise. After is not harmful, just less supported.
What dose should I use on the face?
Around 3–10 J/cm² of red (630–670 nm) per session, three to five times a week. At a measured 30 mW/cm² that is roughly two to five minutes. More is not better.
Can red light replace GHK-Cu or GLOW in a skin protocol?
They act differently — light on mitochondria, the copper peptide on signalling and collagen synthesis — and both are studied separately for skin. Most skin protocols that include one include the other; neither replaces the other.
Is a home panel as good as a clinic bed?
A good panel with published wavelengths and measured irradiance covers the face, a limb or a muscle group well. A clinic bed covers the whole body at once and is more consistent. For most goals the home panel, used consistently, wins on adherence.
Does red light help sleep?
One small trial in athletes reported better sleep scores and higher melatonin after two weeks of evening whole-body red light. It is plausible and unproven. Sleep hygiene and the sleep goal page move more.
Want these built into a plan for you?
If a panel or a clinic bed belongs in your plan, the protocol says which wavelengths, which days and what it sits next to — and your physician says whether it is right for you. €399, follow-up included.
Build my protocol Book a 15-minute call