Shedding Light on Hair Growth: The Science Behind Laser and LED Therapy

Shedding Light on Hair Growth: The Science Behind Laser and LED Therapy

Posted by Jackie Kim on

Today we answer the question: Does laser or led therapy for hair growth really work?

You’ve probably seen red light hair combs or helmets claiming to help grow your hair. It sounds like a gimmick right? That’s honestly what I thought, but so many of you had asked, so we looked into it. And through our research we found that light therapy for hair is legitimate. And it isn’t as complicated as it sounds either.

There are many similar sounding terms. LEDs or lasers, low-level laser light therapy, red light therapy for hair growth – it's all basically the same thing.

The gist is this - if you expose hair follicles to a low level of red light, they are stimulated to grow. And it has been proven in multiple double-blind sham-controlled trials.


What is laser or light therapy for hair growth?

The scientific term for this therapy is low-level laser- or light - therapy. Or LLLT.
And LLLT includes red light in the visible spectrum as well as near-infrared light.

It has long been known that LLLT can promote tissue repair and has beneficial effects for wound healing, nerve regeneration, and joint pain relief (Avci et al. 2014).


Why red light?

Red light has the longest wavelength in the visible light spectrum. And it is believed the longer wavelength can penetrate deep into the scalp cells better.

Near-infrared light also works: and near-infrared light is just light that is a little longer in wavelength than red light and so it is believed it can penetrate deeper than red light can.

However, no comparison studies have been conducted between the two to say one is better than the other (Pillai and Mysore 2021).


How do we know LLLT work?

Like so many medical breakthroughs, the benefit of light on hair growth was found by accident.

In 1967, a Hungarian physician named Endre Mester was investigating whether a low-power ruby laser that emitted red light at wavelength 694nm could be carcinogenic. He shaved his mice as part of his experiment. To his surprise, the laser did not cause cancer, but instead improved the animal’s hair growth (Avci et al. 2014).

What. a. Nice. surprise.

Another observation that made people realize the value of light for hair growth was something called “Paradoxical Hypertrichosis.” This is actually an unwanted side effect that can occur when people try to use laser to remove hair.

In laser hair removal, the hair is stimulated with a powerful light and the melanin in your hair absorbs that light energy to convert it into enough heat to damage the hair follicle. That’s how laser hair removal works.

But in cases where not enough light is absorbed to damage the hairs, the hairs actually can grow stronger in density and thickness in response to the light and heat (Avci et al. 2014).


How does LLLT work?

Let's take a quick detour into the life of hair: hair follicles undergo repetitive lifecycles and each cycle has three stages.

The first is anagen which is when hair is actively growing from the hair follicle. It then enters the catagen phase where hair stops growing and separates from the hair follicle.

It then enters the telogen phase which is the resting phase. About two or three months into the telogen phase, the hair falls out and the cycle begins again (hopefully). So basically the lifecycle of your hair is growth, maturity and death.

This is the key: LLLT is thought to stimulate re-entry into anagen from telogen, prolong the duration of anagen, and prevent premature catagen development. In other words, it is believed to keep more hair cells for longer in anagen - the growth phase. LLLT treatment can lead to increases in hair density, hair diameter as well as decrease in hair shedding.


This sounds awesome! But - how exactly does LLLT work to do this?
The answer is that no one really knows exactly. But several mechanisms have been investigated.

Studies show red and near infrared light can be absorbed by the enzyme cytochrome c oxidase which is found inside the energy-producing part of our cells called the mitochondria.

This light absorption causes nitric oxide to be pushed out from cytochrome c oxidase so that the enzyme can function better.

And that enhanced enzyme function leads to multiple changes including increased cell proliferation, changes in levels of growth factors, and better oxygen flow to tissues (Avci et al. 2014, Liu et al 2019).


Other studies suggest LLLT increases vasodilation and blood flow to the skin and scalp.

Another finding showed that LLLT moderated the expression of an enzyme that converts testosterone to DHT which is implicated in androgenic alopecia, also known as male pattern baldness.

And yet another study suggested LLLT decreased inflammation which is implicated in alopecia areata, which is an autoimmune disease (Avci et al. 2014).

So there are a number of possibilities on why laser and LED therapies can help maintain a fuller head of hair. But we don’t know for certain how they work.


Lasers versus LEDs versus Red Light?

Lasers and LEDs are just two different types of light sources. You’d use a laser if you need a focused beam to travel distance - like laser pointers. Or like in hair removal if you want to specifically heat a single hair follicle. On the other hand, LEDs emit more diffused light beams.

Online, you may see debates on light sources such as lasers versus LEDs.
But in this context of hair growth, really, the main point is to deliver steady illumination of red light over the scalp and at a low power.

High power lights can damage hair follicles and moderate power light can be inhibitory which is why low power light therapy is used. Laser, LED, red light - that distinction matters less.

Okay, then what’s low-power exactly? And how should it be used?


Specifically, for low level light therapy, power density is between 3 to 90mW/cm2 with each treatment session lasting 15-20 mins at a time, three times a week, for 6 months in duration.

Keep in mind that Individual devices will have their own instructions. These instructions are based on the parameters tested in double-blind sham controlled trials, which had positive effects on hair growth (Pillai and Mysore 2021).

Too much of a good thing is not good in this case. In a meta-analysis (a study of studies), a comparison was conducted between those who had treatment greater than 60 minutes per week versus those who had treatment less than 60 minutes.

And this is a striking fact: The ones who had less than 60 minutes of treatment had better hair growth than those who had more than 60 minutes! (Liu et al. 2019) As mentioned, light therapy can encourage hair growth, inhibit it or damage follicles based on the amounts, so just follow instructions and don’t go overboard.


Lasers have more focused light than LEDs. Most studies have been conducted with lasers whereas none have been conducted with LEDs alone, but some studies have been conducted with helmets that contain both lasers and LEDs (Pillai and Mysore 2021, Lanzafame et al. 2013, 2014).

For the most part, red light therapy is the same thing as low-level laser (light) therapy, although light in the near-infrared wavelength can also be used to the same effect.

The wavelength of light determines its color and typically, a red light of wavelength 650nm or 655nm is used in home-based LLLT systems which is just based on what companies have decided to use. Studies investigating LLLT have used wavelengths ranging from 630nm to 660nm which are shades of red light, with positive effects, and there isn’t a direct comparison study showing certain wavelengths of red light are better than other ones.

Near-infrared wavelengths such as 810nm have also been studied, but again, there has been no comparison study to see if near-infrared is better than red light (Avci et al. 2014, Liu et al. 2019).

Overall, you want to choose systems that have been cleared by the FDA and clinically proven in a double-blind, sham-controlled trial.

Note that for devices, instead of using something called a placebo or a vehicle, they use something called a sham. A sham looks like a real device but instead of low power red light at the scalp, no light reaches the scalp from the sham device.


Helmet vs Comb

Currently both comb type and helmet type home-based LLLT systems are available. Note that in meta-analyses that compare helmet type to comb type LLLTs, no differences in effect sizes were found suggesting both are about equally effective (Liu et al. 2019).


LLLT vs Minoxidil

In another study, they tested 3 treatment scenarios, a light therapy helmet by itself, 5% topical minoxidil by itself, as well as the combination of both light therapy and minoxidil.

And the study found that both were similarly effective alone, but the combination led to the best effects (Pillai and Mysore 2021). Indicating perhaps that LLLT helmets can be about as effective as minoxidil and you can double up with minoxidil for an even greater hair growth boost. Hence, LLLT can be used in combination with other treatments for even better effects.


Who does it work for?

Keep in mind that these LLLT combs and helmets have only been shown to work in clinical trials in those with androgenetic alopecia, also known as male pattern baldness.

About 50% of males over the age of 40 experience male pattern baldness. And while it’s called “male” about 75% of females over the age of 65 have androgenic alopecia.

Good thing is that LLLT has been shown in double-blind trials to work in both men and women with androgenic alopecia (Lanzafame et al. 2013, Lanzafame et al. 2014).

What is androgenetic alopecia? It’s basically your body producing too much of an androgen called DHT, which leads to hair loss. Other hair loss drugs like finasteride work by inhibiting the formation of DHT. Androgens are known as male sex hormones even though women have androgens as well.

Men usually notice thinning hair on the top of their heads and around the temples. On the other hand, ladies tend to experience a more even hair loss, with the top part of their hair looking wider, but their frontal hairline usually stays put.

The other FDA approved treatments for androgenic alopecia include drugs minoxidil and finasteride. Hair transplants are the other treatment alternative.

In theory, LLLT may work for other types of hair loss, but LLLT for other types of hair loss besides male pattern baldness haven’t yet been subjected to clinical trials, although it has been tested in animal models.

For example, LLLT was used to treat chemotherapy induced hair loss in rats and hair regrowth started 5 days earlier in laser treated rats compared to sham treated rats.

LLLT has also been used to treat a mouse model of alopecia areata, and hair regrowth was observed in laser treated mice but not in sham treated mice (Avci et al. 2014). Alopecia areata is an autoimmune condition where the immune system attacks hair follicles resulting in hair loss.

So if you have other types of hair loss other than androgenic alopecia, LLLT may still work for you.

How long does laser hair growth last?

Just like minoxidil (Rogaine) or finasteride (Propecia), any hair growth benefitsyou obtain with LLLT will last only as long as you maintain treatment. This doesn’t mean you will lose all the hair growth all at once, but that hair will slowly revert back to the normal baseline as it sheds when you stop using the LLLT.

Avci P, Gupta GK, Clark J, Wikonkal N, Hamblin MR (2014). “Low-Level Laser (Light) Therapy (LLLT) for Treatment of Hair Loss.” Lasers Surg Med. 46(2): 144-151.

Lanzafame RJ, Blanche RR, Bodian AB, Chiacchierini RP, Fernandez-Obregon A, Kazmirek ER (2013). “The growth of human scalp hair mediated by visible red light laser and LED sources in males.” Laser in Surgery and Medicine. 45(8): 487-495.

Lanzafame RJ, Blanche RR, Chiacchierini RP, Kazmirek ER, Sklar JA (2014). “The Growth of Human Scalp Hair in Females Using Visible Red Light Laser and LED Sources.” Lasers in Surgery and Medicine 46:601-607.

Liu K, Liu D, Chen Y, Chin S (2019). “Comparative effectiveness of low-level laser therapy for adult androgenic alopecia: a system review and meta-analysis of randomized controlled trials.” Laser Med Sci. 6: 1063-1069.

Pillai JK, Mysore V (2021). “Role of Low-Level Light Therapy (LLLT) in Androgenetic Alopecia.” J Cutan Aesthet Surg 14(4): 385-391.

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