While both types of light sources (incandescent LEDs and true coherent laser diodes) emit light energy, researchers and authors for the most part agree that biologic effects are most profoundly observed when treatments are performed with true coherent laser diodes vs incandescent LED light sources. In my practice, we've observed positive effects of lasers on hair follicles for over 15 years. Without getting too technical, coherency is one of the unique properties of laser light (see wikipedia.com/laser), in addition to polarization. When comparing laser devices for hair growth, consumers should look for information on how many 'true' coherent laser diodes are in the device as it is believed that those types of light sources are likely to be many times more effective and powerful on the hair follicle than their weaker incandescent LED light sources. Some studies suggest that LEDs may actually have an OPPOSITE effect--like *decreasing* blood flow instead of increasing it (Pontinen).In other words, for hair growth... lasers are "for go," LEDs are "for show."Look also for non-focused/unfocused laser diodes vs those with a narrow spot beam. Unfocused lasers will spread their energy over a wider area which is helpful for treating zones such as the scalp.Support for this concept is found in the most well respected textbook on Laser Therapy by Tuner / Hode as well as these scientific research papers summarized in this linked whitepaper [excerpt below]:These international laser experts and researchers agree that incomparison, laser light therapy is far superior to LED therapy, as indicatedby the studies of these researchers’ published work. Literature:Bihari - LED’s, when compared to lasers, demonstrate a much lower efficacy.Kubota - found there was no difference between control and LED 840 nmgroups.Berki - found the positive effects from laser therapy were not seen whenirradiating the cell cultures with normal monochromatic (LED) light of the samewavelength and doses.Muldiyarov - Analyzed cases where the rats were treated with ordinary red lightand found there was no essential differences from the control group.Haina - compared to the 22% increase in positive laser effects, the increase inthe incoherent (LED) group was less than 10%.Laakso - ACTH and B-endorphin levels were significantly elevated in the LLLTgroups but not in the LED group.Pöntinen - 670nm laser induced a temporary vasodilation and increased bloodflow; however, LED at 635nm with doses between 0.68 and 1.36 J/cm2decreased blood flow at least for 30 minutes after irradiation.Lederer - found that incoherent light of the same wavelength and power densityshowed no influence.Rosner - found that non coherent infrared light was ineffective or had adverseeffect.Nicola – Non-coherent light of the same wavelength and dose was lessfavourable.Onac - The therapeutic window appears to be narrower for monochromatic noncoherentlight.The most important part of treating yourself with lasers for hair growth is to receive a baseline "HairCheck" cross-sectional bundle measurement so you can determine the results of the therapy on your hair follicles without having to wait a full year of treatment.
