Red Light Therapy for Hair Growth: The Long and Short of It



According to the American Hair Loss Association, approximately 65% of men will experience some degree of hair loss, or alopecia, by age 35. That number rises to 85% by age 50. Hair loss in women, while receiving much less attention, is surprisingly prevalent, with women making up 40% of all hair loss sufferers.


Hair loss is often dismissed, both by society in general and by the medical community in particular, as a simple fact of life and inevitable byproduct of aging. While this is true to an extent, this pervasive sentiment ignores the fact that the psychological repercussions of hair loss can be devastating. To illustrate the profound effect hair loss can have on a person’s body image and self-confidence, it is estimated that up to 8% of cancer patients refuse chemotherapy if there is a risk of hair loss.


While hair loss is one of the most common reasons for dermatological consultation, there are few options for treatment. And the treatments that do exist are often invasive, expensive, ineffective, or all of the above. 


There is some good news, however. Exciting new research is showing red light therapy to be a safe and effective treatment for hair loss. Before we get into the specifics of red light therapy and hair growth, let’s get a handle on how we grow hair - and how so many of us come to lose it. 

A Brief Overview of Hair

You might already know that hair grows out of the hair follicle. The hair follicle is a tunnel-shaped mini-organ embedded in the epidermis and extending into the dermis of the skin. The following are the various parts of the hair follicle and associated structures, and their functions: 


  • Dermal papilla: specialized cells at the base of the hair follicle that play a central role in hair formation, growth, and cycling;
  • Matrix: contains the proliferating cells that make up the hair and internal root sheath;
  • Internal root sheath: layer of keratinized cells that protects the hair. It disintegrates where the sebaceous glands meet the hair shaft;
  • External root sheath: a tubular extension of the epidermis that surrounds the entire hair follicle;
  • Bulb: the base of the hair follicle;
  • Bulge: a reservoir containing epithelial stem cells located partway up the shaft of the hair follicle;
  • Arrector pili muscles: responsible for goose bumps, they allow the release of heat and sebum;
  • Sebaceous glands: exocrine glands that secrete sebum, a fatty, waxy mixture that lubricates the hair and the skin.

The growth cycle occurs in three phases. During the anagen phase, also known as the growth phase, the hair begins to grow from the root of the follicle and out the surface of the skin. This phase lasts three to seven years. The catagen, or transitional phase, lasts two to four months, during which hair growth slows and the hair follicle shrinks. The telogen, or resting phase, occurs when the hair falls out and the hair follicle begins to produce a new hair. This phase lasts between three and four months. 


The most important cells of the hair reside in the papilla. These cells send signals to the epithelial stem cells located in the bulge. These stem cells produce progenitor cells, which are a type of cell that can differentiate to form various specialized cells. In this case they differentiate to form amplifying cells that penetrate deep into the dermis. They then further differentiate to form matrix cells, which produce the hair. 

What Causes Hair Loss?

There are 3 main types of hair loss: androgenetic or androgenic alopecia, alopecia areata, and chemotherapy-induced alopecia. Let’s take a brief look at the prevalence and causes of each type.

Androgenetic alopecia (AGA)

This type of hair loss is more commonly known as male or female pattern baldness. As its name implies, it is genetic, and involves the sex hormone androgen. Androgen is the main hormone responsible for the sexual development of men. It also has a variety of functions in both sexes, however, including regulation of hair growth. 


It’s believed that AGA is caused by increased androgen activity, particularly dihydrotestosterone (DHT). Elevated levels of DHT can cause, among other things, premature shrinking of the hair follicles in the scalp, also called follicular miniaturization. These shrunken follicles produce thinner, shorter-lived hairs called vellus hairs, replacing the more robust terminal hairs normally produced in the scalp.


Another factor in AGA is a genetically-predetermined shortening of the anagen phase, as well as a lengthening of the telogen phase (i.e. the time between a hair falling out and a new one arising). 


AGA is the most common form of hair loss, affecting 50 million men and 30 million women in the United States alone. 

Alopecia areata (AA)

AA is an autoimmune disease in which the body’s T-cells attack the hair follicles, causing hair to fall out. However, the hair follicle is not destroyed, meaning hair can grow back. 


According to the American Academy of Dermatology Association, AA has been associated with vitamin D deficiency, as well as other conditions such as vitiligo, asthma, hay fever, Down syndrome, thyroid disease, and atopic dermatitis. Family history is one of the biggest factors associated with AA. There is also evidence that race is a factor, with a higher prevalence in black and Hispanic populations. 


AA affects approximately 2% of the US population. It also affects women more than men, at a ratio of 2.3:1.

Chemotherapy-induced alopecia (CIA)

The role of chemotherapy is to attack rapidly-dividing cancer cells. Unfortunately it does not differentiate between cancer cells and healthy cells. Given that the matrix of the hair follicle has the highest mitosis rate of any organ, its cells are a ripe target for chemo. This is why hair loss is such a common side effect of chemotherapy. 


CIA occurs in approximately 60% of patients undergoing chemo treatment. The vast majority will see regrowth within 3-6 months. Although rare, there are cases of permanent hair loss. This is usually due to high-dose chemotherapy or its combination with certain drugs, and is likely caused by damage to the stem cells of the hair follicle.

Common Treatments for Hair Loss

Let’s take a quick look at the various treatments currently available for hair loss.

Minoxidil (Rogaine)

This topical treatment is considered to be fairly effective in the treatment of AGA. Currently there is insufficient data to support its effectiveness for AA and CIA however. It is generally considered safe. 


While the exact mechanisms are unclear, minoxidil is believed to help with hair growth by vasodilation (widening of blood vessels), allowing more oxygen to reach the hair follicles. It also appears to increase the size of hair follicles, reversing the effects of follicular miniaturization. 

Finasteride (Propecia)

An oral treatment, finasteride works by preventing testosterone from being converted to dihydrotestosterone (remember, DHT is the androgen responsible for follicular miniaturization). While minoxidil is used exclusively to regrow hair, finasteride can also prevent hair loss. Both treatments are considered safe to use together. It is generally only used for AGA.

Corticosteroids

Corticosteroid injections are the most common treatment for AA. They work by reducing inflammation around the hair follicle and by suppressing the immune system. Topical steroid creams can also be used to reduce inflammation and encourage hair growth

Hair transplant

This treatment involves removing individual hairs or a strip of hair from one section of the scalp and transplanting it onto another section. It is considered to be quite effective in the treatment of AGA. It can also be used to treat localized AA, as well as CIA in cases where hair loss is permanent. 


While the effects are permanent, this is the most invasive and expensive of all the treatments. It can cost anywhere from $4,000 to $20,000. As with any surgical procedure, hair transplants can be painful, and carry some risk, including infection, scarring, and nerve damage. 

Scalp cooling

This is the most common treatment for CIA. The way it works is fairly simple. Patients place a cold cap or a scalp cooling system on their head before, during, and after chemotherapy treatments. The cold temperature constricts the blood vessels in the scalp, thereby reducing the amount of chemo that reaches the hair follicles. Research indicates that scalp cooling can reduce or prevent hair loss in 50-65% of patients. 


While these treatments are known to be effective, they don’t always produce the desired results. Luckily, red light therapy is finding its way into the spotlight as both an effective standalone treatment, and a way to bolster the results of the treatments listed above. Let’s take a look at why red light therapy for hair growth is making waves - both literally and figuratively.

How Does Red Light Therapy Work for Hair Growth?

Red light therapy involves the harmless irradiation of the skin with red and near-infrared (NIR) light. Light at these wavelengths penetrates the skin deeper than any other wavelength, all the way to the cells’ mitochondria.


Within the mitochondria, the treatment causes a biochemical reaction that helps it use oxygen more efficiently to produce adenosine triphosphate, or ATP. ATP is known as the body’s energy currency, the vehicle that powers the many functions of each and every organ. This increase in energy allows the body to function more optimally. Just as you are more efficient and capable when your energy levels are high, the same occurs at a cellular level. But how exactly does red light therapy affect hair growth? 


This 2019 article by Dr. Michael Hamblin in Clinical, Cosmetic, and Investigative Dermatology provides a wonderfully detailed account of the role of red light therapy in the treatment of the three types of alopecia. Here are the main takeaways.

Red light therapy and and androgenetic alopecia

It seems red light therapy causes the time the hair follicle spends in the anagen phase to increase. This may be due to the ability of red and NIR light to stimulate the mitochondria in stem cells located in the bulge of the hair follicle. 


One of the most destructive things to cells is oxidative damage. Because stem cells have a longer life than other types of cells, they must be extra resistant to oxidative damage. For this reason, stem cells have an anaerobic metabolism, which is the process of creating energy when oxygen is limited or unavailable. This is characterized, among other things, by low mitochondrial activity. Red light therapy appears to galvanize the mitochondria in the stem cells of the hair follicle, increasing their activity and triggering biogenesis, or the creation of new mitochondria.


Accompanying this increased metabolic activity is a sudden need for oxygen. Stem cells are clustered together in what’s called a niche, a microenvironment that interacts with and regulates stem cells. Because the hair follicle’s stem cell niche is hypoxic (low oxygen), the stem cells must migrate to find oxygen to feed their new sudden hunger for it. This migration into more oxygen-rich environments allows for increased ATP synthesis and, subsequently, more activity in the anagen phase of the hair growth cycle.


There is also evidence that red light therapy causes a transient increase in reactive oxygen species (ROS). A buildup of ROS can cause damage to the cell’s DNA, RNA, and proteins, and can even cause cell death. However, it’s theorized that this temporary increase after irradiation with red and NIR light causes your body’s own antioxidant defense mechanisms to kick into gear. This temporary increase in ROS may play a role in the differentiation of progenitor cells, encouraging them to transform into amplifying cells and then matrix cells, which produce hair. 


Red light therapy is also well-known to reduce inflammation. New research suggests that inflammation may play an important role in female pattern baldness, and is one of the factors that differentiates the condition from the male version. 

Red light therapy and alopecia areata

As is the case with autoimmune diseases in general, the environment in which the hair follicle is found in people suffering from AA is proinflammatory. This occurs when your cytokines (proteins that help regulate immunity and inflammation) favor inflammation. Remember that some inflammation is good. It protects the body by flooding the affected area with white blood cells in order to fight infection and promote healing. However, chronic inflammation occurs when these same white blood cells begin to attack healthy cells. And abnormal inflammatory response is one of the keystones of autoimmune diseases. 


As mentioned above, red light therapy has well-documented anti-inflammatory effects. Not to mention the temporary increase in ROS that kick starts your body’s natural anti-inflammatory response. Red light therapy also increases blood flow to the scalp, allowing for greater access to oxygen by the mitochondria in cells within and surrounding the hair follicle. Another benefit to mitochondria functioning more efficiently to produce energy is that it increases production of anti-inflammatory and antioxidant agents, which are then carried to the hair follicle. 


We mentioned earlier that red light therapy can alter the mitochondrial metabolism of the stem cells in the hair follicle in order to produce ATP. This can have an effect on the macrophages of the cell. You might remember from biology class that macrophages are the cellular organisms that detect, engulf, and destroy pathogens and dead cells. There are two subcategories of macrophage phenotypes, M1 and M2. M1 macrophages have a pro-inflammatory effect, while M2 macrophages play an opposite role, mitigating the inflammatory response and repairing damage. It appears that red light therapy may change macrophage phenotypes from M1 to M2, thus creating a less inflammatory environment. 

Red light therapy and chemotherapy-induced alopecia

Evidence suggests that red light therapy can help reduce apoptosis during chemotherapy. Apoptosis is a type of programmed cell death in which the cell is essentially broken up into fragments to be taken away and disposed of. Chemo works by inducing apoptosis in cancer cells. However, this means that it can also cause the death of healthy cells, including those in the hair follicle. 


This reduction in apoptosis is likely due to an increased amount of anti-apoptotic proteins in the mitochondria. 


While you might think that by this logic, red light therapy would also inhibit cell death in cancer cells, there is currently conflicting evidence of this. It seems red light therapy’s effect on cancer cells may depend on the type of cancer as well as the strength of red light irradiation. However, there is increasing evidence of positive effects of red light therapy on cancer cells, through different mechanisms. And red light therapy is starting to be recognized as a safe intervention for various side effects of cancer treatment


Finally, once chemotherapy is complete, red light therapy can be used to help regrow hair by improving blood flow to the scalp to stimulate hair follicles, and by the mechanism described above in which stem cells are stimulated and the anagen phase is lengthened. 

Specific Studies on Red Light Therapy and Hair Growth

The following represents a small sample of the ever-growing body of research investigating red light therapy as a safe and effective treatment for hair loss.


  • A 2014 study in which 47 women with AGA had either LED red light therapy applied to their scalp at 655 nm, or a sham treatment, every other day for 16 weeks. The active group showed significant improvement in hair counts compared to the control group.
  • Another 2014 study produced similar results, this time in both men and women. Researchers found a significant increase in hair density among participants, as well as self-reported improvements in thickness and fullness of hair, independent of sex. 
  • A 2020 study analyzed the various factors that might affect the effectiveness of red light therapy on AGA. It was found that duration of session, light pulsing, and energy fluence (number of joules per square centimeter) have a significant therapeutic effect on AGA.
  • A 2016 review of red light therapy and hair regrowth concluded that red light therapy is a safe and effective treatment for men and women suffering from AGA who have not responded to or were not tolerant of standard treatments.
  • Another review from 2014 showed similar findings. Researchers hypothesize that the main mechanism involved is the stimulation of epithelial stem cells in the bulge of the hair follicle, as well as increased anagen activity.
  • A 2018 study looked at red light therapy in combination with minoxidil. Results showed a significant increase in recovery from AGA as well as higher patient satisfaction in those having undergone the treatment compared to those in the control group
  • A 2003 study on red light therapy and AA found that participants regrew hair 1.6 months earlier in irradiated areas compared to non-irradiated areas. 
  • Finally, a 2017 study on chemotherapy patients found that those undergoing red light therapy treatment showed 2.6 times more hair growth than those in the placebo group, with no adverse effects. 

There are hundreds more studies demonstrating the effectiveness of red light therapy, particularly with regards to AGA. While more research is needed on the effects of the treatment on AA and CIA, the current findings are certainly promising. And with red light therapy, there is very little to lose, and a lot to gain.

Risks of Red Light Therapy

Across the thousands upon thousands of studies on the various benefits of red light therapy, there is one common thread. The treatment is considered safe for daily use, and has no major risks or side effects. The most common side effects are sensitivity of irradiated areas and eye sensitivity. The former is temporary, and the latter is mitigated by protective eyewear (every Rouge panel comes with eye protection).


Rouge red light therapy panels are actually FDA-registered as class-II medical devices for the treatment of various ailments, including muscle spasms, minor muscle and joint aches, and pain and stiffness associated with arthritis. 


As always, you should check with your doctor before beginning any course of treatment. 

Other Benefits of Red Light Therapy

When we say you have nothing to lose and a lot to gain with red light therapy, boy do we mean it. The treatment boasts a veritable laundry list of benefits, with the body of research supporting its claims growing larger by the day. Some of these benefits include: 


  • Skin rejuvenation, wound, and scar healing;
  • Muscle growth, performance, and recovery;
  • Weight loss;
  • Hair growth;
  • Cognitive health;
  • Immune health;
  • Hormones and sex drive;
  • Pain and inflammation;
  • Mental health and depression;
  • Sleep disturbances;
  • Eye health;
  • Oral and dental health.

Moreover, many people start red light therapy treatment for one issue only to discover unexpected improvements in other areas. For an overview of red light therapy and its various benefits, check out this article.

How You Can Benefit from Red Light Therapy for Hair Growth At Home

The key to seeing results from red light therapy is consistent and continued use. And until recently, the only red light therapy devices available were industrial-sized behemoths. Of course, that meant treatment necessitated a visit to a clinic or spa, often at an exorbitant price. 


Rouge Red Light Therapy has captured the power and efficacy of clinical treatments, but in a compact - and affordable - package. In fact, Rouge’s panels are among the most powerful on the market, according to recent tests. Remember the study above which notes energy fluence (joules/cm2) as a factor influencing hair growth? The Rouge Pro has more than double the energy fluence than the leading competition. 


With a Rouge red light therapy at-home device, you can commit to a consistent red light therapy regimen necessary to promote proper hair growth, in the comfort of your own home, and for pennies a day. 


You can choose to focus on targeted areas such as the scalp with a small, portable panel, or you can opt for the full-body treatment and help improve your health and well-being from head to toe. Whatever your goals - or budget - we’ll work with you to find the device that meets your needs (you can check them out here). Talk to one of our friendly RougeCare agents today and see what you can gain from red light therapy. 



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