Wavelengths explained
Every LED mask is sold on its colours of light. This guide explains what each colour is, how much research sits behind it, and which wavelengths the 21 masks in our UK directory actually publish.
Updated 1 Nov 2026. Luma Index doesn't test or rank masks. This guide isn't medical advice.
Wavelength in one minute
Light is described by its wavelength, measured in nanometres (nm). Visible light runs from violet at about 400 nm to deep red at about 700 nm. Beyond that is near-infrared, which you can't see. LED masks use visible and near-infrared light only; they don't use ultraviolet, the part of sunlight that tans and burns.
Different wavelengths are absorbed by different molecules in the skin, so they're thought to have different effects. As a general rule, longer wavelengths (red and near-infrared) travel further into skin than shorter ones (blue). The process is called photobiomodulation: light absorbed by cells is thought to change how they produce energy and, in turn, collagen [1].
How deep light reaches depends on the wavelength, the light's strength and your skin. Brand claims such as "penetrates up to 10 mm" are marketing statements, usually without a measurement behind them.
Each colour, what it's for
Red, about 630–660 nm
The most studied colour for fine lines, texture and tone. A classic double-blind trial using clinic panels at 633 nm and 830 nm reported less wrinkling and more collagen than a sham light [2]. Two recent sham-controlled mask trials, one using red alone (660 nm) and one red plus near-infrared (630 and 850 nm), also found effects on wrinkles [3] [4].
Near-infrared, about 810–880 nm
Invisible, so a mask's near-infrared LEDs can look dim or off while working. Usually paired with red in wrinkle studies; 830 nm is the most common choice. Near-infrared guide
"Deep" near-infrared, about 1,064–1,072 nm
A newer addition to masks. There's much less published research on it for facial skin, and most of what brands cite is their own testing.
Blue, about 415–465 nm
Used for blemishes because it's absorbed by molecules made by acne bacteria. Reviews disagree on how strong the evidence is [5] [6]. Blue-violet light carries more caution than red for the eyes and for pigmentation in darker skin [1]. Safety guide
Yellow or amber, about 580–610 nm
Marketed for redness and "calming". Far less research than red or blue, and few studies test it alone.
Green, about 520–532 nm
Marketed for uneven tone and pigmentation. Very little independent research for facial use.
In the UK, masks can be sold for cosmetic benefits (how skin looks) but not to treat conditions such as acne or rosacea unless they're registered with the MHRA as medical devices. In November 2025 the MHRA said no LED face masks were registered [7]. That's why UK product pages say "appearance of blemishes" rather than "treats acne".
What UK masks use
Counted from the wavelengths each brand publishes, across the 21 masks in our directory:
| Light | Masks | Wavelengths published (number of masks) |
|---|---|---|
| Red | 21 of 21 | 633 nm (10), 630 nm (8), 660 nm (3), 650 nm (1), 655 nm (1) |
| Near-infrared | 20 of 21 | 830 nm (13), 850 nm (6), 880 nm (1), 940 nm (1) |
| Deep near-infrared | 6 of 21 | 1,072 nm (5), 1,064 nm (1) |
| Blue | 16 of 21 | 415 nm (10), 465 nm (3), 460 nm (2), 440 nm (1), 463 nm (1), 485 nm (1) |
| Yellow / amber | 9 of 21 | 590 nm (4), 605 nm (2), 580 nm (1), 592 nm (1), 600 nm (1), 610 nm (1) |
| Green | 5 of 21 | 520 nm (2), 532 nm (2), 525 nm (1) |
4 masks use only red and near-infrared light. 6 offer five or more colours.
Combinations and "more colours"
- Purple, cyan, white: usually two or three LED colours lit together (for example purple = red + blue), not a new wavelength. Check which LEDs are actually on.
- Simultaneous or in turn: some masks run colours together, others cycle through them. The time each colour gets matters more than the number of colours.
- More colours, less of each: a mask has a fixed number of LED positions. Adding colours can mean fewer LEDs of each, unless the mask uses multi-chip LEDs that switch colour.
- Evidence follows the combination tested: most wrinkle research used red, near-infrared or both. Results from one combination don't automatically carry over to another.
Reading the numbers
- Peak wavelength
- The "633 nm" figure is the wavelength the LED emits most strongly. Real LEDs give off a spread of wavelengths around it.
- Tolerance (± nm)
- How far the actual peak can vary from the stated figure. Only 14 of the 83 wavelength figures in our directory come with a tolerance.
- A range instead of a number
- "Red 620–750 nm" covers the whole red colour band rather than describing the LED. Treat it as not disclosed.
- Wavelength isn't strength
- Two masks at 633 nm can deliver very different amounts of light. Strength is irradiance (mW/cm²) and dose (J/cm²): see the specifications guide. A 2025 analysis of 27 LED skin studies found doses varied more than a thousandfold and none checked their device's output independently [8].
Questions to ask
- Which exact wavelengths does it use, in nanometres, and with what tolerance?
- How many LEDs of each colour, and are they lit together or in turn?
- Can you use red and near-infrared without blue if you don't need it?
- Is any study of the mask, or of these wavelengths, published where you can read it?
- For the less-studied colours, what is the claimed benefit based on?
Sources
- Unlocking the Power of Light on the Skin: A Comprehensive Review on Photobiomodulation. Hernández-Bule ML, Naharro-Rodríguez J, Bacci S, Fernández-Guarino M, International Journal of Molecular Sciences 2024;25(8):4483.
- A prospective, randomized, placebo-controlled, double-blinded, and split-face clinical study on LED phototherapy for skin rejuvenation. Lee SY, Park KH, Choi JW, et al., J Photochem Photobiol B 2007;88:51–67.
- Role of photobiomodulation application frequency in facial rejuvenation: randomized, sham-controlled, double-blind, clinical trial. Bragato EF, … Fernandes KPS (10 authors), Lasers in Medical Science 2025;40(1):170.
- Clinical study to evaluate the efficacy and safety of home-used LED and IRED mask for crow's feet: a multi-center, randomized, double-blind, sham-controlled study. Park SH, Park SO, Jung J-A, Medicine (Baltimore) 2025;104(7):e41596.
- Light Therapies for Acne. Posadzki P, Car J, JAMA Dermatology 2018;154(5):597–598 (Clinical Evidence Synopsis).
- Utilization of light-emitting diodes for skin therapy: systematic review and meta-analysis. Ngoc LTN, Moon J-Y, Lee Y-C, Photodermatology, Photoimmunology & Photomedicine 2023;39(4):303–317.
- LED mask ads banned over acne and rosacea claims. BBC News (Jennifer Meierhans).
- Methodological issues in visible LED therapy dermatological research and reporting. Grimes DR, PLOS ONE 2025;20(9):e0332995.
Directory figures are counted from our 21 UK mask listings and update as listings change. Summaries are written by Luma Index. See the research page for the full evidence library, including each study's limitations.