The science of red light
Red and near-infrared light therapy (RLT / PBM) is neither a miracle nor esoterica. It's a well-described photobiological effect with clearly measurable parameters — and clear limits. Here's what we know about it.
How it works: light, mitochondria, ATP
Red light (630–660 nm) and near-infrared light (810–850 nm) penetrate tissue and are absorbed by cytochrome c oxidase — the last enzyme of the respiratory chain in mitochondria. Absorbing a photon releases nitric oxide bound to the enzyme, which unblocks electron transport and lets the cell produce more ATP, its energy currency.
A side effect is a short, controlled rise in reactive oxygen species (ROS). That acts as a signal — it triggers the cell's repair and adaptation pathways.
Hormesis and the Arndt-Schulz curve
RLT is a textbook example of hormesis: a mild stressor improves function, a strong one degrades it. The dose response is therefore not linear but biphasic — described by the Arndt-Schulz curve.
- • Too little energy — no measurable effect.
- • The therapeutic window — maximum benefit.
- • Too much energy — the effect declines and can reach zero.
In practice this means one thing: longer ≠ better. Doubling the session time doesn't double the result; it usually makes it worse.
Wavelengths and penetration depth
| Wavelength | Penetration | Typical use |
|---|---|---|
| 630 nm | surface | skin, scars, surface inflammation |
| 660 nm | skin and subcutis | collagen, healing, skin quality |
| 810 nm | deep | nerve tissue, deeper muscle layers |
| 830 nm | deep | healing, circulation, joints |
| 850 nm | deepest | muscles, joints, post-exercise recovery |
Combining several wavelengths in one panel covers surface and deep tissue at the same time. That's why our panels mix all five wavelengths on a single chip.
How the dose is calculated
The dose is given in joules per square centimetre (J/cm²) and the maths is simple:
dose [J/cm²] = irradiance [mW/cm²] ÷ 1000 × time [s]
Irradiance is a property of the panel and drops with distance. At 30 cm our panel delivers roughly 85 mW/cm² — so a 25 J/cm² dose takes about five minutes. For an exact number for a specific model and goal, use the dosing calculator.
What the research supports — and what it doesn't
The strongest evidence is for skin quality and collagen production, wound healing, reduced muscle soreness after exercise and faster recovery. It is weaker or inconclusive for systemic claims such as weight loss, detoxification or treating chronic disease. Differences between studies most often come down to dose — many negative studies used a dose outside the therapeutic window.
Safety and limits
- • Don't look straight into the diodes without eye protection.
- • Don't exceed the recommended time — it won't strengthen the effect.
- • Consult a doctor if you're pregnant, have a cancer diagnosis, photosensitivity, or take photosensitising medication.
- • RLT is not a replacement for medical care. The information on this page is educational and is not medical advice.
"Medical-grade" panels
Medical certificates aren't issued for large, non-targeted panels — only small devices aimed at a specific diagnosis carry them. That doesn't mean lower efficacy. What actually tells you something about a panel is measured irradiance, the wavelength mix, real power draw from the socket, and independent spectrometric measurement.