Hair Thrives Under Forest Light
- Thomas P Seager, PhD
- Jul 12
- 7 min read
Green, red, and near-infrared light energizes hair follicles
Anatomy of the Hair Follicle
Hair grows from tiny organs called hair follicles that are embedded 1/8" to a 1/4" (4-7 mm) below the surface of the skin. The follicles are rich in stem cells that participate in both the generation and pigmentation of the hair. Hair follicles progress through four cyclical stages:
Phase | Description | Duration |
Anagen | energy intensive growth | weeks for body hair 2-7 years for scalp |
Catagen | transition - shrinking hair follicle | 2-3 weeks |
Telogen | attached, not growing | months |
Exogen | shedding | days |
These stages are essential for adaptation of hair to seasonal changes in temperature and light. Like other mammals, human beings exhibit some seasonality in their hair cycles, adding in the Fall and shedding (e.g., molting) in Spring. However, human hair serves a purpose that is unique from animals.
Human anatomy has several unusual features that suggest our body's are built for a semi-aquatic environment -- i.e., fishing, wading, foraging and birthing in the water. For example, we have subcutaneous fat like dolphins, whales, seals, and manatee to keep us warm in cold water. Our nostrils point downwards to avoid driving cold water straight up against our brains when we dive, and (most impressively) human babies are born with an instinct to swim. It was exactly these anatomic features that allowed our ancient ancestors to survive long Ice Ages at the waters edge, foraging for shellfish, aquatic plants, and finfish rich in the fatty acids that our massive brains require (Cunnane 2005).
Human beings are also unique in the coverage of hair on our bodies. Mammals that live in the water all the time are hairless (e.g., whales), while mammals that live sometimes in the water and sometimes on land have fur (e.g., otters, seals). However, humans are neither hairless nor furry. Our hair is confined almost exclusively to our heads, and there are likely two reasons for it.
The first reason may be that long hair gives a human infant something to hold on to when its Mother is wading through deep water. Wet skin is slippery, but a breastfeeding child is capable of gripping Mom's long hair so that they don't get lost, washed away, or left behind when Mom is in the water (Morgan 1972).
The second reason relates to light. The only part of the human body that is exposed to sunlight when wading in the water is the scalp. The rest of the body is protected from direct sunlight by the water, which absorbs ultraviolet, most visible, and all near-infrared light. Only the scalp remains exposed during the long hours when a body might be spearfishing, foraging, or bodysurfing.
Bald surfers who do not protect their scalp with hats or sunscreen are notorious for experiencing painful sunburns. Kelly Slater, a famously bald surfing champion, markets his own line of zinc-oxide based sunscreen to protect his scalp. By contrast, big-wave surf champion Laird Hamilton, who sports a thick shock of blonde hair, scorns sunscreen altogether.
What most dermatologists overlook is the fact that human hair is the primary mediator between the body and the light environment. A healthy light environment combines sunshine, shady forest light, and darkness. By contrast, an unhealthy light environment is saturated with artificial blue and fluorescent light. The difference between these two may be the primary determining factor between a thick, healthy head of hair, and a thin, receding hair line.
Photobiomodulation for Hair Growth
The molecules in the human body that absorb light are called chromophores. The four most important in the skin are: 1) melanin in the outer layers, which pigments the skin and protects it from ultraviolet damage, 2) cytochrome c oxidase (CcO) in the mitochondria, 3) hemoglobin in your blood, and 4) water. Different wavelengths of light target different chromophores at different depths of skin (Zhang & Wu 2025). For example, ultraviolet (UV) light is incapable of penetrating any further than the outermost layers of the skin, where it is absorbed my melanin. UVA light will darken melanin, which gives skin an almost immediate tan. UVB stimulates the production of new melanin, resulting in a tan several days after exposure, and is essential for photosynthesis of Vitamin D from 7-dehydrocholesterol precursors.
Melanin isn't just one molecule. There are dozens of different types, and they are essential for healthy skin. Several studies have documented the necessity of regular sun exposure for human health, both because it relates to Vitamin D and because melanin is a broad spectrum chromophore that converts light into energy for skin cells. Dermatologists and social media influencers who warn against regular sun exposure are giving poor health advice. However, too much UV without enough protective melanin can damage skin. This explains why shady forest light (green and red/nearinfrared, NIR) is so healthy for human skin. It energizes the melanin without disturbing it.
Green light penetrates further than UV, reaching melanin near the boundary of the dermis and epidermis, where new skin cells are formed. Thus, green and red forest light promote healthy skin and accelerates skin healing. For example, when researchers in Japan tested several different wavelengths of light for healing of burn wounds in rats, they found that green (518 nm) and red (638 nm) worked best.
Both green and red/NIR light have also been observed to promote hair growth. Several clinical trials have observed increased hair thickness and density after several weeks of both green (Tantiyavarong & Meephansan 2024) and NIR photobiomodulation therapy (Tantiyavarong et al. 2024, Torres & Lim 2024).
There are two mechanisms by which good results have been obtained via PBM for hair growth. The first is direct stimulation of skin cells in the dermis and epidermis that provides some portion of the necessary energy to promote hair growth. The second is by promoting angiogenesis -- i.e., the growth of new micro blood vessels in the skin to improve circulation of nutrients in the scalp.
Nonetheless, until January 2026 not one study tested red/NIR wavelengths that would directly target hair follicles themselves. That is, previous studies obtained good results by targeting the outer layers of the skin, but ignored the fact that hair follicles are embedded at depths the 630 nm red light will not reach. To correct this oversight, Korean researchers developed a unique organic LED device that produced only narrowband 730 nm NIR light -- the wavelength they estimated would reach the stem cells in the hair follicles on the scalp. They observed a 92% reduction in an enzyme associated with follicle ageing and increased activity in the human dermal papilla stem cells (hDPC) that promote hair follicle regeneration.
Combining Green, Red & NIR PBM for Hair Follicle Energy
While science proceeds by studying independent variables in isolation, Nature is more complex. There has never been a scientific study of the three wavelengths in combination that have individually been proven to energize otherwise dormant hair follicles and produce thicker, denser hair, faster. While it is clear that existing red/NIT PBM hoods, caps, and helmets waste most of the energy in wavelengths that entirely miss the hair follicles, what's not yet obvious is whether a combination that simulates shady forest light might be most effective for recovery of lost hair.
The MyGreen Hair Growth Hood was developed to test this hypothesis. It is equipped with narrowband green (532 nm), red (660 nm), and NIR (732 nm) wavelengths to expose the human scalp to the same light environment of the shady forest that was likely essential for our ancient ancestors good health.
The Hair Growth Hood is an untested hypothesis. We can make no claims about whether it will be better than the clinical trials proving the efficacy of the wavelengths used individually, which is why the Hood is being offered on a discounted, trial basis to those intrepid customers willing to test the hood for their own educational and entertainment purposes, and share their results with me.
References
Cho EH, An J, Chi Y, Choi KC. Wearable textile-based phototherapy platform with customized NIR OLEDs toward non-invasive hair loss treatment. Nature Communications. 2026 Jan 10.
Cunnane SC. Survival of the fattest: the key to human brain evolution.
Fushimi T, Inui S, Nakajima T, Ogasawara M, Hosokawa K, Itami S. Green light emitting diodes accelerate wound healing: characterization of the effect and its molecular basis in vitro and in vivo. Wound Repair and Regeneration. 2012 Mar;20(2):226-35.
Morgan E. The descent of woman. Souvenir Press; 1972.
Rohringer S, Holnthoner W, Chaudary S, Slezak P, Priglinger E, Strassl M, Pill K, Mühleder S, Redl H, Dungel P. The impact of wavelengths of LED light-therapy on endothelial cells. Scientific reports. 2017 Sep 6;7(1):10700.
Tantiyavarong J, Charoensuksira S, Meephansan J, Hanvivattanakul S, Rayanasukha Y, Boonkoom T, Tantisantisom K. Red and green LED light therapy: A comparative study in androgenetic alopecia. Photodermatology, Photoimmunology & Photomedicine. 2024 Nov;40(6):e13004.
Tantiyavarong J, Meephansan J. The Efficacy of Green Light Emitting Diode on Androgenetic Alopecia: A Pilot Study. RSU International Research Conference 2024.
Torres AE, Lim HW. Photobiomodulation for the management of hair loss. Photodermatology, photoimmunology & photomedicine. 2021 Mar;37(2):91-8.
Zhang WF, Wu H. Full-Spectrum phototherapy in hair loss management: a systematic review of wavelength-dependent mechanisms, clinical efficacy, and future directions. Lasers in Medical Science. 2025 Sep 19;40(1):367.
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