Quick definition: Red light therapy uses low levels of visible red light, usually around 620–700nm (660nm is common), to support the look of skin and scalp. It does not burn or heat tissue the way surgical lasers do. Researchers have studied it for fine lines, skin texture, and thinning hair, with promising but still developing evidence.
What is red light therapy?
Red light therapy (RLT) shines low-intensity red light onto the skin. It sits under the broader scientific umbrella of photobiomodulation, the term researchers use for light that changes how cells behave without damaging them. Cleveland Clinic describes red light therapy as a treatment that uses low levels of red light to reportedly improve the skin's appearance.
Red light is visible, which is why red light devices glow a deep red. Its close cousin, near-infrared light, sits just beyond what the eye can see. Many devices combine the two, and some add blue light for oil-prone skin. Each color is defined by its wavelength, measured in nanometers (nm).
How red light therapy works
The leading explanation is that red and near-infrared photons are absorbed by mitochondria, the energy centers inside cells. Harvard Health explains that the light is believed to stimulate mitochondria, which may help calm inflammation and support collagen, the protein that keeps skin firm and supple.
A few factors shape what reaches the target tissue:
• Wavelength. Longer wavelengths travel deeper. Red light (around 660nm) reaches the upper layers of skin and the scalp, while near-infrared goes further.
• Dose. How much light energy is delivered per square centimeter, often called fluence, matters. Research in this field points to a dose window: too little does little, and more is not automatically better.
• Distance and contact. Light spreads and weakens with distance, so how close the source sits to skin changes what actually arrives.
• Consistency. Studies typically use repeated sessions over weeks or months, not a single session.
Red light therapy for face: what studies found
Facial use is the most common reason people try red light. In a controlled trial published in Photomedicine and Laser Surgery, Wunsch and Matuschka treated 113 volunteers twice a week with red or broad red-to-near-infrared light for 30 sessions. Compared with 23 controls, the treated groups showed improved skin complexion and skin feeling, reduced roughness measured by profilometry, and higher collagen density measured by ultrasound. Notably, the broader spectrum did not outperform red light alone.
Commonly reported red light therapy benefits in the research literature include smoother-looking texture, softer-looking fine lines, and more even tone. Cleveland Clinic lists potential uses such as reducing the look of wrinkles and fine lines and improving acne, while also noting the evidence base is still growing:
"more quality studies with larger numbers of people are needed" — Cleveland Clinic
Red light therapy for hair growth: what the research says
Search interest in "does red light therapy help hair growth" is high, and the research is worth reading carefully. Most hair studies use low-level laser therapy (LLLT) devices, such as laser combs and helmets, often in the red range, and focus on androgenetic alopecia (pattern hair loss).
A 2019 meta-analysis in Lasers in Medical Science by Liu and colleagues pooled 11 double-blinded randomized controlled trials and reported a significant increase in hair density versus sham devices, in both men and women:
"LLLT significantly increased hair density in AGA." — Liu et al., Lasers in Medical Science
Interestingly, the authors found lower treatment frequency performed better than higher frequency, another reminder that more light is not always better. These are findings about specific medical devices in specific study populations. They do not mean every red light product will produce the same results, and hair shedding can have many causes. If you are losing hair suddenly or in patches, see a board-certified dermatologist to find out why.
For more on how hair cycles through growth and rest, see our entries on the anagen phase and the hair follicle.
Red light in beauty and personal care
Red light shows up in several formats:
• In-office treatments. Dermatology and aesthetic clinics use large, high-output panels. Cleveland Clinic notes that at-home products may be less powerful than devices used by skin professionals.
• LED face masks and panels. These flood the whole face with light at once. See our LED light therapy entry for how they compare.
• Handheld wands. These let you target specific zones, such as crow's feet or smile lines, and are often paired with a serum.
• Scalp devices. Combs, caps, and helmets aim light at the scalp through the hair.
660nm red light is a popular choice across these formats because it sits in the visible red range that penetrates the upper skin layers well. Safety-wise, red light is not ultraviolet, so it does not tan or burn. Harvard Health advises keeping the light out of your eyes and using eye shields if provided. If you are pregnant, take photosensitizing medication, or have a skin condition, check with a dermatologist first.
How Reseen fits in
Reseen builds devices around VIPE™ precision light. For the face, Glow is a handheld wand with 12 × 660nm red, 12 × 460nm blue, and 12 × 1064nm near-infrared emitters, plus gentle 108°F warmth and an EMS mode, used in 5-minute sessions 3–5 times a week for firmer-looking, more radiant skin. Many users notice texture and radiance changes around week 4.
For the scalp, Weave is a light comb with 39 × 660nm red emitters, and Halo (coming soon) is a wireless cap liner with 128 red and 128 blue light points. Both are cosmetic tools designed to support scalp health for a healthier-looking scalp and fuller-looking hair.
Frequently asked questions
Does red light therapy for face actually work?
Controlled studies have reported improvements in skin roughness, complexion, and collagen density measured by ultrasound. Evidence is promising, but experts say larger, higher-quality trials are still needed. Results depend on wavelength, dose, and consistent use over weeks.
Does red light therapy help hair growth?
A 2019 meta-analysis of randomized trials found low-level laser therapy increased hair density in people with androgenetic alopecia compared with sham devices. Those results apply to the studied devices and conditions. Anyone with noticeable hair loss should see a dermatologist for a diagnosis.
What is 660nm red light?
660nm is a wavelength of visible deep-red light. It is widely used in red light devices because it falls in a range that reaches the upper layers of skin and the scalp without heat damage.
How often should you use red light therapy?
Follow your device's instructions. Studies typically use several sessions a week over one to several months, and at least one hair meta-analysis found lower treatment frequency worked better than higher frequency.
Browse every term in the Reseen glossary.
Sources
1. Red Light Therapy: Benefits, Side Effects & Uses — Cleveland Clinic, 2021
2. Red light therapy for skin care — Harvard Health Publishing, 2025
3. A controlled trial to determine the efficacy of red and near-infrared light treatment in patient satisfaction, reduction of fine lines, wrinkles, skin roughness, and intradermal collagen density increase — Wunsch A, Matuschka K. Photomedicine and Laser Surgery, 2014
4. Comparative effectiveness of low-level laser therapy for adult androgenic alopecia: a system review and meta-analysis of randomized controlled trials — Liu KH, Liu D, Chen YT, Chin SY. Lasers in Medical Science, 2019
This article is for general education and is not medical advice. Reseen devices are cosmetic devices and are not intended to diagnose, treat, cure, or prevent any disease. If you have a skin or scalp condition, talk to a board-certified dermatologist.