If you've shopped for a red light device, you've seen numbers like 660nm and 850nm on the box. They're the most useful spec on any red light product, and usually the least explained. Here's what they mean in plain English, and how to use them when you compare devices.
What does "nm" mean?
"nm" stands for nanometers, the unit used to measure the wavelength of light. Different wavelengths are different colors. Shorter wavelengths look blue, longer ones look red, and past the red end of the spectrum the light becomes near-infrared, which our eyes can barely see, if at all.
Red light therapy (the clinical name is photobiomodulation) mostly uses two bands: red light, roughly 600–750nm, and near-infrared light, roughly 750–1100nm (Serrage et al., 2019, a review in Photochemical & Photobiological Sciences).
The big difference: how deep the light goes
Wavelength affects how far light travels into the body. Shorter, visible wavelengths stop closer to the surface, while longer, infrared wavelengths reach deeper into tissue (VCA Animal Hospitals). The same 2019 review notes that near-infrared light can penetrate up to about 5mm through tissue.
How much light actually gets there also depends on the device's power, your dog's coat and skin, and how close the light sits to the body. Light spreads out as it travels, which is one reason fit matters: a panel that lies flat against the back beats one that floats above it.
660nm: visible red light
- You can see it. It's the red glow in our videos of Maya.
- It stays closer to the surface, where it's absorbed by the skin and the tissue just beneath it.
- It sits squarely in the red band used throughout photobiomodulation research.
850nm: near-infrared light
- You mostly can't see it. At most, you might notice a faint, dull red on the LEDs.
- It travels deeper into tissue than red light does.
- It's often paired with red light, so a single session covers both depths.
Do you need both?
Not necessarily. There's very little published research comparing single-wavelength and dual-wavelength home devices, and almost none in dogs. So the practical questions matter more than the spec sheet:
- How big is your dog? Bigger dogs have more back (and chest) to cover, and getting the size right matters more than the number of wavelengths.
- Where do you want coverage? Back only, or back and chest?
- What will you keep up with? One wavelength and one button is the easiest routine to stick with.
- What does your vet think? They know your dog; we don't.
How to read a red light product listing
- Look for listed wavelengths. If a listing doesn't say what wavelength it uses, you don't know what you're buying.
- Check for a timer. An automatic shut-off keeps every session the same length.
- Compare the panel to your dog. Measure from the base of the neck to the base of the tail and check it against the panel size.
- Be realistic about power. Consumer devices rarely publish a measured power output (ours included), and none of them match a clinic laser. Our research post explains why that matters.
- Look for a real guarantee. The only way to know whether your dog will use it is to try it.
Where Solaura's vests fit
| Vest | Wavelengths | Coverage | Sizes |
|---|---|---|---|
| Back Therapy Vest | 660nm red | Back | Small (up to ~20 lbs), Medium (~20–55 lbs) |
| Pro Vest | 660nm red + 850nm near-infrared | Back and chest | Medium and Large (~30–80 lbs) |
The Pro Vest also has four light modes: steady, a slow "breathe" pulse, 10Hz and 40Hz. Steady light is the simplest place to start, and your vet can weigh in if you're curious about the others. Not sure about size? See the Back Therapy Vest size guide or the Pro Vest size guide.
The short version
660nm is visible red light that stays closer to the surface. 850nm is near-infrared light that travels deeper. Neither number tells you everything, but a listing without them tells you nothing.
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Every Solaura product comes with a 30-day money-back guarantee, because the only way to know if it suits your dog is to try it.
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This article is for general information only and isn't veterinary advice. Always talk to your veterinarian before starting any new wellness routine for your pet. These statements have not been evaluated by the Food and Drug Administration. Solaura products are not intended to diagnose, treat, cure, or prevent any disease.