Everything you need to know about red light therapy for hair growth
Men may notice a receding hairline, thinning around the crown, or gradual loss across the top of the scalp. Women more commonly notice a widening part, reduced hair density, or thinning across the top of the scalp.
The most common cause in both men and women is hereditary pattern hair loss. In men it is usually called male pattern hair loss, and in women female pattern hair loss or androgenetic alopecia.
But hair can be lost for many other reasons, including alopecia areata, illness, hormonal changes, medication, childbirth, nutritional problems, tight hairstyles and periods of excessive shedding.
Most of the stronger research on red light therapy for hair growth has been conducted on men and women with pattern hair loss. There is much less evidence for many other causes of hair loss.
So does red light therapy actually help grow hair? There is reasonably good evidence that repeated red light or low level light therapy can improve hair density in some people with male or female pattern hair loss.
The results are not dramatic for everyone, it often takes months rather than days, and it should not be viewed as a guaranteed way to restore a full head of hair. The American Academy of Dermatology's overview of red light therapy also takes a cautious position, noting that repeated treatments may help some people with hereditary hair loss while results vary.
What is red light therapy for hair?
Hair devices typically place red light directly over the scalp using lasers, LEDs, or a combination of the two. The wavelengths used in hair studies are commonly around 630nm to 660nm, with 655nm appearing repeatedly in clinical trials.
The strongest evidence is generally for devices designed specifically to expose the scalp, such as helmets, caps and laser combs.
How can red light influence hair follicles?
The exact mechanism is still being investigated. One of the main theories behind photobiomodulation is that red light is absorbed by light sensitive molecules associated with mitochondria, the structures involved in cellular energy production.
This may influence mitochondrial activity, ATP production, nitric oxide signaling and other cellular pathways. A detailed scientific review, Photobiomodulation therapy and hair growth, discusses several of the possible mechanisms researchers are investigating.
Hair follicles move through different phases
The anagen phase is the active growth stage, while the telogen phase is a resting stage before a hair eventually sheds. Researchers have investigated whether photobiomodulation may help increase the proportion of follicles in the anagen growth phase and influence cellular signalling associated with hair growth.
A laboratory study using 655nm red light, Effects of red light on the hair growth and Wnt beta catenin signalling pathway, found increased hair shaft elongation in cultured human hair follicles and effects on biological pathways involved in hair growth.
Photobiomodulation appears capable of influencing biological processes involved in hair growth, while researchers are still working out exactly which mechanisms matter most.
Does red light therapy actually work for hair growth?
There is now enough research to say that red light therapy is more than just a social media hair trend.
A 2024 systematic review and meta analysis of low level laser and LED therapy for alopecia looked at 38 studies involving 3,098 people.
Of those participants, 2,930 had androgenetic alopecia.
The researchers found a significant improvement in hair density with low level laser or LED therapy compared with placebo in people with androgenetic alopecia. However, there was not enough information to draw the same conclusion for other forms of alopecia.
That distinction is important.
It seems that red light therapy appears to be a promising option for male and female pattern hair loss. The evidence is considerably less certain for other causes of hair loss.
The American Academy of Dermatology says some, but not all, studies show that repeated red light treatments can regrow some hair over time in people with hereditary hair loss. It also emphasizes that red light will not regrow a complete head of hair.
What have studies found in men?
One of the better known studies looked specifically at men.
The randomized trial of 655nm light therapy in men with androgenetic alopecia recruited 44 men between 18 and 48 years old.
The treatment device contained 655nm lasers and LEDs and was worn over the scalp for 25 minutes every other day for 16 weeks.
Forty one participants completed the trial.
The active treatment group experienced a significantly greater increase in hair counts than the placebo group.
The researchers reported approximately a 35% to 39% increase in hair growth relative to the comparison used in their analysis.
No adverse events were reported.
What have studies found in women?
Women should not assume that research conducted in men automatically applies to female pattern hair loss.
Fortunately, women have also been studied separately.
A randomized trial of 655nm light therapy in women with pattern hair loss recruited 47 women between 18 and 60 years old.
The researchers used essentially the same 655nm laser and LED helmet protocol used in the male trial: treatment every other day for 16 weeks.
Forty two women completed the study.
The average increase in hair count was significantly greater in the active group than in the placebo group.
The researchers described the difference as a 37% increase in hair growth compared with placebo and concluded that the response was similar to what had previously been observed in men.
Another randomized study involving 45 women with female pattern hair loss divided participants into three groups:
- 5% minoxidil
- low level light therapy
- both treatments together
The light therapy groups used a helmet for 25 minutes, three days per week, for four months.
Both minoxidil and light therapy produced improvements. The combination group performed best on some measures, including clinical hair loss classification and patient satisfaction.
A separate trial involving 90 women comparing 650nm light therapy, minoxidil and the combination also reported improvements in hair density and diameter across the treatment groups, with stronger improvements in some measurements in the combination group.
However, the combination question is not completely settled.
Recent reviews have reached different conclusions about whether adding photobiomodulation to minoxidil consistently produces substantially better results than minoxidil alone.
A 2025 meta analysis of photobiomodulation combined with minoxidil reported improved hair density and diameter with the combination.
Studies including both men and women
One of the larger studies investigated laser comb devices in both sexes.
The randomized controlled trials of laser combs in men and women with pattern hair loss included 128 men and 141 women.
Participants used either laser comb or sham devices across the scalp three times per week for 26 weeks.
Among those included in the final analysis, the treated groups experienced significantly greater increases in terminal hair density than the sham groups.
The researchers found that the improvement was not dependent on whether the participant was male or female. No serious adverse events were reported.
Another 24 week randomized helmet study involving men and women included 40 participants, with 20 men and 20 women.
Hair density and hair diameter increased significantly more with the active device than with the sham treatment. The researchers did report some temporary hair shedding and scalp itching.
How long does red light therapy take to work on hair?
Hair grows slowly. Clinical studies commonly run for around 16 to 26 weeks.
The male 655nm helmet study ran for 16 weeks.
The female 655nm helmet study also ran for 16 weeks.
The larger laser comb trials ran for 26 weeks.
The helmet trial involving men and women ran for 24 weeks.
You should not judge results or a device after two or three weeks. A practical expectation is to think in terms of several months of consistent use rather than expecting rapid visible regrowth.
How often should you use red light therapy for hair?
There is no single scientifically established schedule that applies to every device. Research protocols vary considerably.
Some studies used treatment twice per week.
Several used three sessions per week.
Others used treatment every other day.
One home use laser helmet study used an 18 minute treatment schedule.
Ten minutes with one device is not necessarily equivalent to ten minutes with another because wavelength, irradiance, distance, number of LEDs or lasers and total light dose can differ.
If you are using a red light therapy device for hair, it’s best to follow the schedule recommended for that particular device rather than making something up yourself.
Can you overdo red light therapy on your hair?
More light is not automatically better.
Photobiomodulation is known to show what researchers call a biphasic dose response.
A widely cited paper on the biphasic dose response in low level light therapy explains that lower or moderate doses can sometimes produce a beneficial biological response, while increasing the dose beyond the useful range does not necessarily improve the result.
That does not mean using a hair device for an extra five minutes will make your hair fall out. It means there is no good reason to assume that doubling the recommended session time or using a device repeatedly throughout the day will produce twice the hair growth.
Do you have to keep using it?
Pattern hair loss is progressive. Red light therapy does not remove the underlying genetic tendency toward hair loss.
The American Academy of Dermatology's notes that continued treatment is generally required because the underlying process causing hereditary hair loss continues. Long term maintenance protocols have not been studied as thoroughly as the first four to six months of treatment.
So rather than promising that results will permanently disappear if you stop, the more accurate conclusion is that people using red light therapy for pattern hair loss should expect it to be a long term routine.
What type of red light therapy device is best for hair?
There are several different designs.
Cap or helmet: This is probably the easiest design for regular use. The LED lights sit around the scalp and can expose a relatively large area at once. Caps and helmets have been used in several randomized clinical trials, which gives this category relatively good hair specific evidence.
Laser comb or brush: These devices are moved through the hair manually. A notable advantage is that comb teeth can separate the hair and allow the light to reach the scalp more directly. This feature was deliberately built into the HairMax LaserComb studied in clinical trials. The disadvantage is that it requires more active positioning and may feel tedious compared with putting on a helmet.
General red light therapy panel: A panel can illuminate the scalp and has the advantage of being useful for other home wellness routines. However, most of the stronger hair growth trials have used devices designed specifically for the scalp. Positioning it for a hair session without a stand can be difficult, you will at least need hanging cords, which most panels do come with as standard.
Professional clinic device: Clinics may use larger or specialized laser and LED systems. The advantage is professional setup and guidance. The disadvantage is recurring appointment costs, travel and the need to maintain a treatment schedule.
What about wavelength?
Most of the clinical hair studies discussed above use visible red wavelengths around 630nm to 660nm, with 650nm and 655nm appearing particularly often. Near infrared wavelengths have also been investigated, but the evidence base for consumer hair growth devices is more heavily concentrated around visible red light.
A panel containing 660nm light uses a wavelength very close to those used in several hair studies, but wavelength alone does not make two devices equivalent. Dose, distance, coverage, light delivery through the hair and treatment schedule all matter.
Hair itself can make light delivery more difficult
For photobiomodulation to act on hair follicles, enough light needs to reach the scalp. Existing hair can block or scatter some of that light. This is one reason some laser combs physically separate the hair as they move across the scalp.
The Hairmax study previously mentioned is useful here because the device was designed with comb teeth that help part the hair and expose the scalp to the light.
Caps and helmets solve the problem differently by placing many light sources close to the head. Panels can be a bit trickier to positioning and ensure maximum light exposure to the scalp.
What about other types of hair loss?
This is where the answer becomes much less certain.
The 2024 systematic review of low level laser and LED therapy for alopecia included studies involving androgenetic alopecia, scarring alopecia, alopecia areata, telogen effluvium and hair loss related to chemotherapy.
But almost 95% of the participants had androgenetic alopecia. There was not enough statistical information to perform the same analysis for the other hair loss conditions.
A study involving women with female pattern hair loss and telogen effluvium found a significant increase in hair counts for the female pattern hair loss group, but not for the telogen effluvium group.
What side effects have been reported?
Low level light therapy has generally been well tolerated in hair studies. Several randomized trials, including the female 655nm helmet trial, reported no serious adverse events.
The 24 week study in men and women did report temporary hair shedding and scalp itching in some participants.
The American Academy of Dermatology describes red light devices as generally safe when used correctly, while also noting that we do not yet know everything about the long term effects of repeated use.
People with conditions that make them unusually sensitive to light, or those taking medication that increases light sensitivity, should speak to a qualified healthcare professional before using light therapy.
What do people on Reddit say about red light therapy for hair?
Reddit is useful for understanding what using these devices is actually like. Users share there personal experiences and test different devices. However, it’s worth keeping in mind that personal stories should not be confused with clinical evidence.
Generally, the comments regarding red light therapy for hair growth on Reddit are mixed.
In one Reddit discussion about results from a red light therapy hat, a user said that after six months they saw "absolutely no differences", but by 11 months they believed they were seeing better results.
Another user discussing two months of red light therapy for hair described only "minor improvements" and viewed it more as an additional treatment than the main driver of hair growth.
In another Reddit discussion about red light therapy caps, one user who had used a red light cap alongside minoxidil for around six months described the cap as "pretty disappointing so far."
Another person reported substantial shedding during their first month using a helmet, followed by improvement several months later.
So, in terms of Reddit experiences, results vary, treatment takes time.
Conclusion
Red light therapy for hair growth does not seem like a simple trend that is here today gone tomorrow.
As we’ve shown you, there are randomized controlled trials in men and women. We have studies using helmets, caps and laser combs. The evidence is strongest for androgenetic alopecia, or male and female pattern hair loss.
The overall direction of the evidence suggests that low level red light therapy can increase hair density in at least some people with pattern hair loss. That does not mean it works for every type of hair loss, restores completely bald areas, or produces dramatic regrowth for everyone.
The most realistic way to look at red light therapy for hair is as one potential tool for pattern hair loss that requires consistent use over several months.
Disclaimer
This article is for general educational purposes only and is not medical advice. Red light therapy products are intended for general wellness and lifestyle use unless specifically cleared for a particular medical purpose. Always follow your device instructions and consult a qualified healthcare professional if you have a medical condition, take photosensitising medication, have an eye condition, are pregnant, or are unsure whether red light therapy is suitable for you.