I have covered low-level laser therapy (LLLT) and hair growth on this blog a number of times in the past. A spate of new studies on this subject are increasingly focusing on the appropriate laser light wavelength during treatment.
But results are often conflicting, with blue light (wavelength between 450 and 495 nanometers), red light (wavelength between 620 and 750 nanometers) and even longer wavelength light all finding support. Note that some studies can have small sample sizes, or suffer from bias due to being sponsored by a laser device manufacturer.
Note that most commercially available LLLT laser hair growth products (combs, caps, helmets) are of around 650 nm wavelength. Meaning that they are in the red light spectrum.
LLLT Wavelength: Blue Light > Red Light?
I decided to write this post because of a new surprising April 2017 study from Europe. It found that a UV-free blue light laser (453 nm wavelength) led to hair growth via prolongation of the anagen phase of the hair cycle, but a red light laser (689 nm length) did not do the same. This is a surprise since most LLLT devices on the market use the red light spectrum as I mentioned earlier.
Update: February 2021 — From the same scientists, a new study on 453 nm blue light induced cryptochrome 1 (CRY1) and hair growth benefits.
Update: A June 2021 report finds that blue light therapy is a promising therapy for patients affected by androgenetic alopecia. Moreover, blue light-emitting diodes seem to darken grey hair in some people.
Other Studies on Laser Wavelength and Hair Growth
Also of interest, a 2015 study from South Korea found that 830 nm laser was superior to lower wavelength lasers (of 632 nm, 670 nm and 785 nm) when it came to hair growth in rats.
But a November 2021 report finds that photobiomodulation response from 660 nm is more durable than that from 980 nm.
A 2017 study from Iran tested a new laser scanner device (with a combination 655 nm red laser plus 808 nm infrared laser) by comparing it with a 655 nm red light laser hat. Both products led to hair growth benefits, but the laser scanner was superior. So laser wavelength may make a difference in outcome.
Combining Fractional CO2 Laser and Hair Growth Factors
I discussed fractional lasers and hair growth in a post in 2015. Now a new study from China finds that a combination treatment using carbon dioxide fractional laser treatment plus growth factors is significantly superior to using growth factors alone.