How red light works on skin.

Red light therapy is the everyday name for photobiomodulation: exposing skin to specific wavelengths of visible red and near-infrared light, at low intensity, for a few minutes at a time. There is no heat worth mentioning, no UV, and nothing is stripped, peeled or injected. The light is absorbed by the cells themselves, and the cells do the rest.

It is one of the few skincare technologies that started in clinics and hospitals and then moved into the home rather than the other way round. That history matters, because it means the questions worth asking — which wavelengths, how much, how often — already have answers.

How light changes what skin cells do

Inside every skin cell are mitochondria, the structures that turn nutrients into usable energy (ATP). Red and near-infrared light happens to be absorbed by an enzyme in the mitochondria called cytochrome c oxidase. When that enzyme absorbs light in the 600–900 nm range, the cell's energy output rises for a while, nitric oxide is released, and local blood flow increases.

In skin, the cells that respond most visibly are fibroblasts — the cells that build collagen and elastin. When fibroblasts have more energy and better circulation, they are more active. That is the whole premise of red light therapy for skin: not adding anything from outside, but giving the skin's own repair cells the conditions to do their job.

Light doesn't do the work. It gives the cells that already do the work a better shift.

The wavelengths, and what each is for

"Red light therapy" is shorthand. A well-designed mask uses several wavelengths, because each one reaches a different depth and interacts with a different target.

Red · 630–660 nm

The workhorse. Red light reaches the dermis, where collagen is made, and is the most-studied wavelength for the appearance of fine lines, firmness and overall texture. If you only ever used one setting, it would be this one.

Blue · 415 nm

Blue light barely penetrates — which is the point. It is absorbed by porphyrins produced by the bacteria involved in breakouts, and that absorption is unfriendly to the bacteria. Blue is typically paired with red, which calms the redness that comes with a blemish.

Green · 520–560 nm

Green sits between blue and red in depth. It is used for the look of uneven tone and dullness. The evidence base here is smaller than for red or blue, so we describe it as supportive rather than primary.

Near-infrared · 830–850 nm

Invisible to the eye and the deepest-reaching of the group. Near-infrared is associated with recovery and calm — it is the setting for skin that looks stressed, and for the evenings after sun, wind or a long day.

White · full spectrum

A combined session that runs the whole range at once, for the nights you don't want to choose.

What the research suggests

The clinical literature on light and skin is broader than most people expect. A few studies are worth knowing about, because they shaped how home devices are designed:

• A controlled trial by Wunsch and Matuschka (2014) treated 136 participants with red and near-infrared light twice a week for 30 sessions, and reported improvements in skin roughness and intradermal collagen density compared with an untreated group.
• A split-face, placebo-controlled study by Lee and colleagues (2007) used 630 nm and 830 nm LEDs and observed changes in wrinkle appearance and elasticity, with increases in collagen and elastic fibres on biopsy.
• Papageorgiou and colleagues (2000) compared blue (415 nm) and red (660 nm) light with benzoyl peroxide for mild-to-moderate acne and found the combined light group improved meaningfully over twelve weeks.

Two honest caveats. First, most studies use clinic-grade devices and defined schedules, so results at home depend on using the mask consistently. Second, light therapy supports the appearance and comfort of skin; it is not a treatment for any medical condition, and it does not replace a dermatologist.

How to use it well

The variable that matters most is not intensity. It is consistency. The studies above worked because people showed up several times a week for months.

• Clean, dry skin. Light has to reach the skin, so use the mask after cleansing and before serums, oils or moisturiser.
• Ten minutes, three to five evenings a week. Aeterna's sessions are auto-timed, so the mask ends the session for you.
• Serums afterwards. Skin is warm and circulation is up; this is a good moment for hydrating and peptide serums. Retinoids and acids are best kept to separate evenings.
• Expect weeks, not days. Most people notice tone and texture first, within a few weeks, and firmness and fine lines over eight to twelve weeks.

Is it safe?

Red, blue and near-infrared LED light contains no ultraviolet and, at the intensities used in home masks, does not burn or thin the skin. Aeterna's mask uses flexible medical-grade silicone with shaped eye openings, and the recommended session length keeps exposure well within the ranges used in published studies.

A few situations call for a conversation with your doctor or dermatologist first: pregnancy, a photosensitivity disorder, medication that increases light sensitivity, or an active skin condition under treatment. If a session ever feels uncomfortable, stop.

Which Aeterna is for skin

The Aeterna™ Red Light Neck & Face Mask brings all five wavelengths above into a single device that follows the contours of the face and neck, with ten-minute auto-timed sessions. It is the device we designed for exactly this ritual. See everything for skin in the Skin collection, or read on for how the same light works on hair and muscle recovery.