Red light therapy was invented in 1967. Now that it’s finally getting the attention it deserves, people are asking whether red light therapy is a gimmick or a real therapy.
8,856 red light therapy studies support support its use for reducing wrinkles, acne, depression, demention, and wound-healing time. People naturally ask how one modality can be useful for so many issues. The secret is that red light therapy powers the mitochondria, the energy-making organelles for our cells.
Red light therapy is not a gimmick, but to get the results you want, you need to get the right dose of the right kind of light. These two points are critical. If you get the dose or color wrong, you might not see the results you want. It’s easy to fix this problem, and I’ll show you how.
Does Red Light Therapy Work?
Red light therapy does work for multiple concerns, and is not a gimmick. . There are over 8,000 publications on the US government’s medical publication database website (pubmed.gov) support red light therapy’s use on the skin, hair, bones and brain. The technology goes back to an accidental lab discovery. Dr. Mester discovered that a low energy laser accelerated hair growth in shaved mice. Fifty-five years of research later, the therapy is finally becoming popular.
Does Red Light Therapy Require Lasers?
The first red light therapy discovery used a laser that was accidentally set to a very low energy output. The researchers realized that it was the light, not the heat, that did the healing.
In 2001, NASA commissioned a study of light emitting diodes (LEDs), and whether they could substitute for low energy lasers. The LEDs helps Navy Seals heal faster from the training wounds. LEDs were as effective as lasers at healing the body.
The difference between an LED and a laser is how the devices send light to the target. Lasers send a column of light that concentrates the light into a hot spot. LEDs send light out in a cloud of photons that do not create that hot spot.
Since heat is counterproductive to light therapy, lasers have no advantage over LEDs.
How to Shop for a Real Red Light Therapy Tool
If you are figuring out which type of device to buy, I wrote a complete guide and a shortcut guide just for that purpose. Take a look here:
- The Complete Guide to Choosing a Light Therapy Device and
- The Shortcut Guide to Choosing a Light Therapy Device
How Does Red Light Therapy Work?
Just give me an idea, I don’t want the science
Red light therapy energizes the cellular energy factories that power healing and repair; and it opens the blood vessels, allowing nutrition and oxygen to support more healing and repair.
I want the science
The electron transport chain in the mitochondria slows and fails with injury, disease and aging.
Red light therapy photons absorb in the electron transport chain, adding electron energy back to the energy factory. With the photon energy, the mitochondria is able to ramp up adensoine triphosphate (ATP) production, which gives the cells the energy they need to repair cells and tissues.
In the skin, this produces collagen and elastin. In the bones, this produces fibroblasts. In the brain, this stimulates non-inflammatory immunity that removes plaque and tangles, and energizes neural repair.
Is Red Light Therapy a Pseudoscience?
Red light therapy is not pseudoscience, as thousands of studies support its use for healing.
One reason this is so hard to comprehend is that red light therapy heals so many problems, it seems like it must be a gimmick. Red light therapy heals better than some drugs.
To find the science, you need to know the vocabularly. Red light therapy goes by over 70 names, a state of affairs that makes searching the science a bit tedious. One of the least-used names in the scientific literature is “red light therapy,” compounding the research problem.
Out of the thousands of successful studies that can be found in the links below, I pulled five at random to demonstrate that red light therapy is not psueoscience.
Search for Photobiomodulation Science
“Photobiomodulation” is the use of photons (packets of light) to change (modulate) biology (bio). Search the US government’s scientific database for photobiomodulation, and you will find 2,233 results (as of July 2022).
Click here for a pubmed.gov photobiomodulation search (opens in new window). You can read successful red light therapy studies, such as using photobiomodulation (red light therapy) to:
- reduce neck pain
- accelerated dental healing
- accelerated wound healing
- muscle atrophy recovery
- reduction of brain amyloid plaque deposits
Search for Low Level Light Therapy Science
Click here for a pubmed.gov “low level light therapy” search (opens in new window). There are 7,013 articles as of July 2022. You can read successful red light therapy studies, such as using low level light therapy (red light therapy) to:
- reduce dental swelling
- reduced pain receiving novacaine shots
- increased neural plasticity (brain health)
- prevention and reduction of oral mucositis
- reduction of melasma
Search for Cold Laser Science
Click here to view “cold laser” science (opens in new window).
- improved horse muscle function
- arthritic pain reduction
- Bell Palsy symptom reduction
- increase success rate of vascular dilation surgery
- improved wound healing
Who Uses Red Light Therapy
Did you notice that the “cold laser” science includes horse therapy articles? Veterinarians were one of the first medical groups to adopt red light therapy. Chiropractors, always advocates of non-pharmacological therapies, were also early red light therapy adopters. Veterinarians and chiropractors use red light therapy to speed wound healing and reduce pain.
Spa owners were early adopters of red light therapy. They noted benefits to skin health and rejuvenation. Studies show red light therapy triggers collagen and elastin. Collagen is healthy new tissue, and elastin holds the skin firm.
Biohackers figured out that red light therapy works on the mitochondria, the energy factories in our cells. They adopted red light therapy to recharge their bodies.
Athletes and their trainers adopted red light therapy for injury repair and post exercise healing. Red light therapy reduces delayed onset muscle soreness (DOMS).
What Color is Red Light Therapy?
Red light therapy is a catch-all term for using low-energy light to heal. There are several types of light therapy that fall into the “red light therapy” category. These therapies use red, infrared, blue, green and yellow light.
Light travels in waves. The distance from peak to peak of each wave is the wavelength of that light. Wavelengths of color visible to the human brain are billionths of a meter long (nanometers).
Red Light Therapy Colors
The red in “red light therapy” is 630 nm to 670 nm wavelengths. The exact wavelength does not matter. In fact, the wavelength we absorb changes as we do the therapy. So there’s no “correct” single wavelength. LEDs output ranges of wavelengths, not a single pinpointed color. Red light reaches the skin for rejuvenation, wound healing, and wrinkle reduction. Red is also a part of the arsenal for acne therapy, which also includes blue and infrared light.
Infrared Light Therapy Colors
Infrared is more complicated. Some ranges of infrared work, and some do not. 810 nm, 940 nm and 1070 nm are bioactive, with wavelengths near those points working just as well. Infrared is also anti-inflammatory and stimulates skin and tissue healing.
Infrared at 810 nm and 1070 nm reaches the brain through the scalp and nostrils, having positive effects on people with Alzheimer’s, Parkinson’s and Huntington’s diseases.
Green, Blue and Yellow Light Therapy Colors
The science on blue, green and yellow light is still defining the best wavelengths to use.
Blue light kills bacteria such as P acnes. Green light calms migraines and encourages wound healing.
Yellow light has an anti-redness effect on the skin.
Ultraviolet Light Therapy Colors
Ultraviolet light is therapeutic but is not low energy and is therefore not “red light therapy.”
Dermatologists use UV light to treat psoriasis. UV is not available in home light devices because it is dangerous to the eyes and skin. Blue and infrared can harm the eyes but are available in home devices. UV is more dangerous.
Does Wattage Matter for Red Light Therapy?
Wattage is one of the least understood aspects of red light therapy.
Wattage is the amount of power going into the device.
We care much more about the power coming out of the device rather than what’s going in.
Since red light therapy is “low energy,” a high wattage can be counter productive. But, too little energy is useless.
The better metric is “irradiance,” or how much light reaches the target.
What Strength Should Red Light Therapy Be?
The best irradiance is one-half milliwatt (1/2 mW) to 100 milliwatts (100 mW). So look for the “mW” rather than the wattage. The irradiance is how much photonic (light) energy reaches the skin. The wattage is how much electricity reaches the red light therapy device.
A Secret Trick to Judging Red Light Therapy Strength
To avoid gimmick devices pretending to be real red light therapy, look at the irradiance and treatment time. The weaker the device, the more time you need each session. The stronger the device, the less time you need. So you have a secret weapon to see if the vendor is truthful about its device’s power.
A treatment time of 5 minutes is very fast. This is a powerful device, and likely very expensive.
A treatment time of 15 minutes is normal. This is a normal treatment time for a high-quality device
A treatment time of 25 minutes indicates a weak device, or a difficult to penetrate spot. The only device for which this is a good treatment time is a neoprene brain helmet. It’s just that hard to penetrate the brain, so 25 minutes with that type of device is reasonable. But a panel that takes 25 minutes is too weak.
An Easy Trick to Discover the Light Device’s True Irradiance
Almost all vendors say their devices output greater than 100 milliwatts (mW), but almost all vendors use the wrong type of meter to get this value.
Solar meters are cheap, and almost all vendors use them. Mito Red Light, for example, says that they use solar meters for a relative comparison to other therapeutic devices. To compare apples to apples, they’re forced to use the solar device. Otherwise their numbers seem too low.
But you need to know if your device is really 100 mW, or you will get the wrong dose.
The easy way to solve this problem is to look at time per session. Vendors might amp up their power specs with solar meters, but the real proof is in time. So use the table above to see how powerful the device really is. Five to 15 minutes of time per treatment indicates a strong, healthy device.
It doesn’t matter what the stated irradiance is. The truth is in the treatment times. Using this trick, you can avoid the 100 mW/cm^2 jargon altogether. Should you want to learn how to read irradiance, though, please enjoy my articles on EMF Channel: Irradiance Definition and What is a “Dose” of Red Light Therapy?
Are Cold Lasers as Effective as “Hot” Lasers?
Red light therapy can be a laser or some other form of light. LEDs usually light at-home therapeutic devices. Both lasers and LEDs can output the light the body finds therapeutic.
In the beginning, there were only lasers. When researchers discovered getting equivalent results with LEDs, the science and the markets both opened up to new products. LEDs are cheaper and safer than lasers. That means the functionality that used to be only from lasers is now available in home products.
Studies repeatedly show that LED and laser deliver therapeutic energy.
Laser light reflects at the skin, leaving the amount absorbed equal with LEDs.
The photons of light energy do the healing. Not how fast they get there or how energetic (hot) they are on arrival. Lasers produce photons. LEDs produce photons. Both send healing photons to the body.
A laser output beams of light in one direction. Those beams converge on a spot. The concentration of light is hot enough to burn the skin or blind an eye. That is why we have not had “at home” light therapy with lasers.
An LED sends out light in several directions. The beams do not converge on one spot. They are not hot. They don’t burn anything. LED light is safe because it is “cold.”
The issue is not 100% settled. We don’t yet have absolute proof that anything you can do with a laser you can also do with an LED. Thousands of studies show that LEDs are as effective as lasers.
Red Light Therapy Works on Aging
Low Level Light Therapy (LLLT) is “possibly the ultimate non-invasive approach to treating the skin.” – Dr. Michael Hamblin
There are many benefits to using infrared, red and blue light therapy on the skin. There are no known negative side effects. Red light therapy increases collagen, reduces wrinkles, reduces sagging, evens skin tone, and smoothes pigmentation.
Use Red and Infrared Therapy to:
- reduce wrinkles
- reduce redness
- reduce inflammation
- reduce psoriasis and acne
- reduce fine lines
- reduce pigmentation*
- increase vitiligo skin pigmentation*
- reduce age spots
- reduce photodamage
- improve skin texture
- improve skin firmness
- increase lymphatic system activity
- heal non-melanoma skin cancer
- rejuvenate skin
- speed wound healing
- protect from UV sunburn
- treat UV exposure
*If red light increases unwanted pigment, ensure you are not getting infrared heat. If the light is cool and the situation continues, discontinue infrared light.
Use Yellow/Amber/Orange Light Therapy to:
- reduce wrinkles
- reduce fine lines
- reduce inflammation
Red and infrared light reduce fine lines and wrinkles. They stimulate collagen and elastin, which fill out creases.
In a study of 76 patients, researchers gave red, infrared, or a combination to one-half of each participant’s face. Wrinkles reduced by as much as 36%, and elasticity increased by as much as 19%. The red, the infrared, and the combination group had similar gains. (source)
In another study testing red light in vitro, researchers found that red light alone reversed collagen downregulation, meaning that the skin produced more collagen than normal. Collagen reduces wrinkles and fine lines. (source)
A third study tested the effect of blue, red and/or infrared on the lymph system. They found that stimulation with any of these lights increased lymphatic system activity. That activity correlated with reduced wrinkles, reduced hyperpigmentation, enhanced glow, increased collagen and decreased acne. (source)
Infrared, Red, Blue and Green Light Therapy Work for Acne
Multiple studies using blue, red, infrared, or some combination of these lights show that light therapy heals acne.
Blue light reduces inflammation and kills bacteria. The result is reduced oil and pimples.
Green and blue light kill the bacterium P. acnes, one of the causes of acne. Red and blue combined significantly reduce acne symptoms.
In one study testing blue and red light, blue light, white light, and benzyl peroxide, researchers found that the combination of blue and red light had the greatest ability to reduce acne lesions. The group receiving blue and red at the same time had a 76% reduction in inflammatory lesions. (source, source).
Another study included both blue and red, but treated patients with each color on different days. One day they got red light treatment, and the next session they got blue light treatment. 22 patients receiving alternating red and blue therapy saw an 81% lesion reduction at 12 weeks. (source, source)
In a study of red and infrared without blue light, researchers found that red light had a significant ability to reduce acne, but that infrared light did not. (source)
In one study, researchers treated acne patients with two wavelengths of red light: 635 nm and 670 nm. The patients got a very low dose of energy per session, but they got 112 treatments over a 2-month period (2 times a day for 8 weeks). At the end of the study, the acne blemish count fell 51%. (source) (source)
I’ve put more acne studies in the EMF Light Therapy Dose Database that you can view at this link (opens in a new window).
Red Light Therapy Can Heal Some Eye Conditions
WARNING: Many vendors, enthusiasts and researchers dismiss concerns about eye damage using light therapy. Blue light certainly can harm the eyes. Infrared can cause cataracts over the long term. I err on the side of caution. Talk with your ophthalmologist before exposing your eyes to light therapy.
Red light therapy can enhance an older person’s ability to see color. Older eyes lose the ability to distinguish colors. This is not a disease but just a normal part of the body tiring out with age. The part of the eye that perceives the color blue loses strength with age.
Eyes lose the ability to make energy. The mitochondria are responsible for producing energy. The mitochondria in the eyes tires out. Red light specializes in inducing the mitochondria to make energy. Therefore, red light therapy is a perfect fit for tired mitochondria in the eyes.
In one study, patients received 670 nm red light to the dominant eye. One group was under 40. The other group was over 40. The young people did not experience changes in vision. The people over 40 years old gained back their ability to distinguish the color blue.
Red Light Therapy Works for Pain Relief
Red light therapy has an anti-inflammatory and an analgesic affect on pain. The inflammation reduction reduces pain triggers. The analgesic affect numbs the pain.
Researchers tested red light therapy on breast augmentation patients. Doctors shined 635 nm red light at the incisions while the patients were still on the table. The light doses were relative low.
Patients did a self-assessment 24 hours after surgery. 76% of the patients who had received red light treatment reported at least 30% less pain than the control group. These patients asked for less pain medication too.
Red Light Therapy Works for Hair Growth
Red light therapy helps hair to grow in many types of baldness, but not all types.
In one study, researchers gave balding patients high doses of red light. They received three shades of red: 630 nm, 650 nm and 660 nm. Each patient was treated for 168 days. All patients grew hair by the end of the 24 week (6 months) period. Their hair was thicker and denser than at the start of the study.
In another study, balding women were treated with one shade of 655 nm red light. Each patient received 60 treatments of high dose red light over 16 weeks. On average, the treated women grew 37% more hair than the women in the untreated control group.
Red Light Therapy Can Melt Fat
WARNING: Note the protocol you have to do for this to work. It’s not an automatic freebie!
Red light therapy can induce cells to open micropores through which the triglycerides fall into the spaces between the fat cells. If the user exercises immediate after treatment, she can shed the loosened fat through the lymphatic system. The FDA allows this process in commercial treatments, so it is a proven concept.
It is often not as easy as it sounds. It helps not to eat prior to the session, and exercise after light therapy is required. If you point red light at fat and it does not reduce, look at the eating and exercise schedule. In addition, drink water after therapy to flush the system.
In one study researchers treated patients’ fat with 635 nm red light. The lights were embedded in wraps around the patients’ arms. The dose was relatively low. After two weeks and six sessions, the patients’ arm size reduced from losing fat. Arm sizes dropped an average of 3.7 cm, or 1.4 inches.
In the original study showing how red light affects fat, researchers looked at treated fat cells under an electron microscope. They took pictures of the deflated fat cells that had just let go of their fat and water. It took only a relatively low dose of 635 nm red light to release the fat during a single treatment.
Can You Use Red Light Therapy Every Day?
In many situations, you can use red light therapy every day. Some successful anti-aging and anti-acne studies applied light therapy daily. The majority of studies spread out the treatments to two or three times per week.
For example, this study tested a combination of blue and red light on mild to moderately severe acne. Patients received treatment only twice per week for 4 weeks. The group experienced a mean average non-inflammatory lesion reduction of 34.28%, and a mean average inflammatory lesion reduction of 77.93%.
While you can use red light therapy every day, you might get just as good results doing it less often.
The device you buy for at home use should include the answer to this question. People engineering the lamp know its specifications. They should be familiar with the dosing paradigm to make good recommendations to their customers.
How Long Should You Use Red Light Therapy?
Light therapy is a Goldilocks treatment. Too little or too much are the same as not doing it at all. The dose has to be just right. More is not better. If you know how (or want to learn how) to calculate dosing, you will need to know your device’s specifications. You can get the information on how to dose on my site EMF Channel: What is a Dose of Red Light Therapy? (Opens in new window)
If you don’t want to learn the irradiance, wavelengths, time and distance parameters of light dosing, go by the instructions on your device. No one knows better how to use a light therapy device than the manufacturer.
Can You Overdo Red Light Therapy?
Too much red light therapy can result in making things worse, or just reversing gains achieved to that point where the overdose started. Once the cells fill up with light, the positive response reverses. This usually results in it appearing as if the light is not helping. In fact, it’s not proof of that at all. Improper dosing will stop the healing effects of light therapy.
What Time of Day is Best for Red Light Therapy?
Blue light therapy should be done in the morning. Blue light suppresses melatonin. You need that to feel sleepy, so you don’t want to suppress it at night.
The other colors of green, yellow, red, and infrared can be done at any time. Some people feel no difference using light at any time of day. Some people respond best in the morning, and some at night. The effect is about your biology and response rather than there being a rule as to when to do therapy.
Can You Wear Clothes During Red Light Therapy?
You cannot wear clothes during red light therapy unless you are OK with not getting treatment where the clothes block the light. For face treatments, for example, you can wear clothes because you are not treating your body. Light therapy does not penetrate clothing.
How Long Does it Take to See Red Light Therapy Results?
In the acne study we mentioned earlier, patients received treatments two times per week for four weeks. They experienced a reduction of 34% to 78% inflammatory lesions at 8 weeks. It did not all get better at 8 weeks, that is just when researchers measured results.
In this wrinkle reduction red light study, researchers treat patients with light therapy daily for 12 weeks. The tested group had a significant reduction in wrinkles measured at that point.
In another study of red and infrared for wrinkle reduction on the neck rather than the face, patients received daily treatment for 16 weeks. Wrinkle reduction was significant at 16 weeks when measured.
In a study of infrared applied up the nostril and on the scalp, dementia patients received infrared light therapy for 12 weeks. Both mild and moderately severe dementia patients experienced significant cognitive improvement when measured at 12 weeks.
In a case study of one combative dementia patient, treatment was just two days before significant changes occurred. After two days of infrared and red light treatment through the nose, cognition improved, sense of smell returned, memory scores improved, and stress reduced.
In measuring the blood flow in the head, 6 sessions of red light treatment over 3 weeks resulted in increased blood flow in three cerebral arteries.
Is Light Therapy Like Being in the Sun?
Red and infrared light therapy includes some of the wavelengths that we get from the sun. Only light therapy at a dermatologist’s office includes ultraviolet (UV). UV rays are effective for problems such as psoriasis, but UV is dangerous to the body.
Red light therapy never has ultraviolet rays. The closest it comes is blue light therapy.
Blue light is next to UV on the electromagnetic spectrum. Blue light suppresses melatonin and can cause insomnia. Blue light can damage the eyes.
Can You Tan and Do Red Light Therapy on the Same Day?
Tanning is dangerous and probably should not be done, but if you want the answer: no, you should not do red light therapy and tanning on the same day. Red light is protective against ultraviolet. The theory is that the photoreceptors fill up on red photons, which blocks the UV photons from entering the skin. Red light therapy acts like a sunscreen that protects your skin from tanning and burning.
Does Red Light Therapy Give You Vitamin D?
The body produces Vitamin D when exposed to sunlight’s ultraviolet rays. Red light therapy does not have UV and does not induce the production of Vitamin D.
Can You Get Red Light Therapy from the Sun?
You can get red and infrared wavelengths from the sun. Whether this is therapeutic depends on how much of your skin absorbs that light. These wavelengths are easiest to get in the morning and evening sun, and not in the mid afternoon.
Do Red Light Tanning Beds Work?
Just to be abundantly clear, red light therapy does not tan. The red light beds that look like tanning beds do not emit ultraviolet light. UV is dangerous, and tanning beds are dangerous.
Many Planet Fitness members speak highly of the Beauty Angel red light treatment there.
Can You Just Use a Red Light Bulb for Red Light Therapy?
Light bulbs have two problems that prevent them from being therapeutic. Their light is scattered, so only a portion will reach the target. In addition, they put off quite a bit of heat. You do not want heat. You want photons. I have talked to many biohackers. I do not know of one who has successfully repurposed a light bulb for red light therapy.
Red light therapy reduces skin redness (use acne settings)
Is Red Light Therapy Safe?
Light therapy with LED home devices is safe with a few exceptions mentioned below. Light therapy performed with lasers is dangerous without proper safety procedures.
The FDA designates the low power laser treatment of pain a “nonsignificant risk” for human testing. LEDs are cool to the touch. Low power laser also means Low Level Light Therapy and LED Light Therapy.
LED light therapy:
- does not require drugs
- does not heat the skin (the light heals, not heat)
- is non-invasive
Light Therapy Cautionary Contraindications
An abundance of caution dictates the following people not do light therapy without physician consultation:
- pregnant women
- nursing mothers
- epileptics and those with seizure disorders
- people on photo sensitive medications
- people with tumors (controversial, as LED therapy significantly helps with radiation treatment side effects)
What are the Side Effects of Red Light Therapy?
Blue light decreases melatonin and can damage the eyes. As long as the user wears a complete eye covering, blue light therapy has neither of these side effects.
Infrared light is helpful for pigmentation issues, but can also sometimes cause unwanted pigmentation. If this occurs, stop use of infrared, and add blue if possible.
If there is any chance that you are getting heat from the infrared, create more distance between the device and the skin target. The light heals, not the heat.
Is Red Light Therapy Bad for Your Eyes?
Blue light is harmful to the eyes. Users should wear blackout goggles when doing blue light therapy.
Whether infrared light therapy is harmful to the eyes is controversial. Long-term infrared exposure causes cataracts.
Certainly many studies show that red and infrared heal macular degeneration and low vision. These studies do not establish a safety profile either. I tend to err on the side of caution. Assume the worst and take precautions.
Not sure if you need goggles or dark glasses with your red light therapy? Find out whether you need goggles in my article 1 Way to Know if You Should You Wear Goggles in Red Light Therapy (opens in a new window)
Is Light Therapy Safe for Dogs?
Light therapy is safe for dogs, cats, horses and all mammals, as far I can tell. Light therapy was a veterinarian treatment for dogs long before the home devices came on the market for humans. Dogs respond to red and infrared with lower inflammation and pain relief. Red light therapy is popular with horse owners.
Treatment times might be shorter for dogs than for humans. If you are unsure, you can do more minutes each day until you reach the human dose. An easier way to handle the dose issue for dogs is to buy a cold laser designed for animals.
How Red Light Therapy is Therapeutic
We have photoreceptors in our skin called chromophores. The chromophores have maximum sensitivity to absorbing red and infrared light.
- chromophore proteins in the cell mitochondria absorb photons
- electron transport increases
- nitric oxide increases
- adenosine triphosphate (ATP) increases
- blood flow increases
- reactive oxygen species (ROS) increases
- signaling pathways activate
- can activate stem cells which repair tissue
Red and infrared light therapy creates an energy-production cascade of events. Photoreceptors in the body’s energy-making mitochondria absorb the light. When enough photons reach the cells, the body goes into energy production mode. The result is more energy and nitric oxide. Blood flows easier, and brings oxygen and nutrients to areas that need it.
Researchers also believe that light therapy triggers the body’s messaging systems. DNA kicks off protein creation. Light therapy triggers the body to create amino acids that form proteins, which are the building blocks of life.
Blue light causes a DNA messaging mechanism to clog. It stops signaling, and after a long chain of events, unhealthy cells die off. This is why blue light is good for acne, especially when that acne involves the P. acnes bacterium.
To learn more about the photochemistry and photobiology of light therapy, see my article Is LED Therapy Effective? Yes. Yes it Is. (study summary)
How Red Light Therapy Works for So Many Health Concerns
Red light therapy stimulates the energy production in the cells. The photoreceptors absorbing the light photons are inside the mitochondria. The mitochondria are inside the cells. When the photoreceptors absorb a sufficient amount of light, the body makes energy, increases blood flow and delivers oxygen and nutrients nearby. This is why red light therapy is successful at treating so many conditions. It’s giving the body the energy it needs to heal itself.