Walk down any wellness aisle and you will see the same two numbers printed on boxes: 660nm and 850nm. They sound like part numbers. They are actually wavelengths — and they behave quite differently once they leave the device.

660nm: the visible red

660nm sits at the red end of the visible spectrum. You can see it, which is why red LED masks glow red. It is absorbed close to the surface — roughly the top few millimetres of skin — which is why visible red light is the one you see on face masks, neck wraps and handheld devices aimed at the skin itself.

850nm: the near-infrared you cannot see

850nm is just past the red end of what the human eye can detect. A near-infrared panel can look almost dark while it is running, and that surprises people. It penetrates deeper, which is why NIR is the wavelength you find on panels, mats and belts aimed at larger areas of muscle and tissue rather than the surface of the face.

How to tell what a device really uses

• Look for the number, not the colour. “Red light therapy” on a box tells you nothing about the wavelength. Check the specification for 630, 660, 810 or 850nm.
• Count the LEDs, not the modes. A mask advertising seven colours usually has a handful of LEDs per colour. Density is what determines how much light reaches your skin.
• Check whether both are used at once. Many panels run visible red and NIR together, which is fine — just be aware which one you actually wanted.

Which should you choose?

If your goal is a face mask routine, visible red (630–660nm) is the wavelength you want, and a well-made mask will state it. If you are buying a panel for a larger area, look for dual-band devices that combine visible red with 850nm near-infrared.

A note on expectations

Light therapy devices are general wellness products. They are not medical devices and they are not intended to diagnose, treat, cure or prevent any disease. If you are pregnant, photosensitive, taking photosensitising medication or under medical care, speak to a healthcare professional before you start.

Questions about which of our devices uses which wavelength? Email support@dembor.cn and we will tell you exactly what is inside.