Red Light Therapy - Wavelengths & dose
Wavelengths and dosing: 660nm, 850nm and the joules that matter
What the numbers on a device actually mean: why 660nm and 850nm come up so often, and why joules - the light dose - are central to the science.
Two numbers dominate discussions of red light therapy: wavelength, measured in nanometres, and dose, usually measured in joules per square centimetre. Understanding what each describes makes marketing far easier to read. Throughout this lesson, dose refers to a dose of light energy, not any drug or supplement.
Wavelength: 660nm and 850nm
Around 660nm sits in the visible red band, and around 850nm in the near-infrared band. These particular figures appear so often partly because they fall near ranges studied in the research and partly because manufacturers have converged on them. Red wavelengths are generally studied for more superficial targets and near-infrared for deeper ones, reflecting how far each tends to travel into tissue. The exact best wavelength for a given outcome is still debated.
Dose: the joules that matter
Dose depends on how intense the light is, how close the source is, and how long the exposure lasts. Two devices quoting the same wavelength can deliver very different doses to your skin. This is why research reports energy delivered rather than simply naming a colour of light - and why quoted times and distances only mean something alongside the device's actual output.
- Wavelength describes which light; dose describes how much energy reaches the target.
- Intensity falls off quickly with distance, so the same panel delivers less the further away you sit.
- A number printed on a box is a claim, not a measurement - independent output figures are more informative.
This is educational material about how the science is measured, not instructions to use any device or a recommended dose for anyone. It is not medical advice. Consult a qualified professional about your individual situation.
Sources for this classroom
Educational content only. Not medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before changing your health regimen.
