Red, Blue and Near-Infrared: What Each Wavelength Does
Every light therapy device lists numbers in nanometres, and almost none of them explain what the numbers mean. A nanometre is simply where that light sits in the spectrum, and the number matters because different wavelengths reach different depths and are absorbed by different things.
Blue, around 415 nm
Blue light does not travel far into skin. It is absorbed by porphyrins produced by Cutibacterium acnes, the bacterium involved in inflammatory acne. In a randomised study of 107 patients published in the British Journal of Dermatology in 2000, daily fifteen-minute sessions of combined blue and red light produced a mean improvement of 76% in inflammatory lesions after twelve weeks, better than blue light alone, white light, or 5% benzoyl peroxide cream.
Red, around 630 to 660 nm
Red light penetrates further, into the dermis, where it is the wavelength most often studied for skin texture, tone and collagen. Most of the published photorejuvenation work sits in this band, usually combined with near-infrared.
Near-infrared, around 830 to 1060 nm
Near-infrared is invisible and goes deepest, which is why it appears in studies on muscle and joint tissue as well as skin. In facial studies it is normally paired with red rather than used alone.
Why devices combine them
Because the targets are different. A blue-only device has little to offer someone concerned about fine lines; a red-only device does nothing to acne bacteria. The combined studies consistently outperform single wavelength arms, which is why most serious devices carry more than one.
Two numbers worth checking
- Irradiance, given in mW/cm². This is how much light actually lands on skin, and together with time it determines the dose.
- Coverage. A device that treats the whole face at once delivers its dose in one session. A small handheld does not.
A device that publishes neither number is asking to be taken on trust.
Kivorla devices are general wellness devices, not medical devices. Individual results vary.