The Science Behind Photobiomodulation: Can Light Really Make Hair Grow?
Around the world, 40% of men display visible hair thinning by age 35. The same is true for women, but by age 40. This can be caused from a wide range of factors: anything from poor diet to a natural hair loss caused by advancing age. For the millions of people facing thinning hair, solutions may feel elusive and impossible. However, recent technology has emerged that show promise at combatting this problem by encouraging regrowth using nothing but red and near-infrared light. Known as low-level laser therapy, LLLT has made significant progress in the last 2 decades, rapidly moving from a laboratory experiment to a consumer-grade product. But does it actually work?
The Premise
The premise of LLLT is based on a well known phenomenon called photobiomodulation. The science is simple. Inside the mitochondrial membrane of hair follicles, we can find a specific type of enzyme called cytochrome c oxidase. Also known as Complex IV, it accepts electrons from cytochrome c and reduces molecular oxygen to form water. This then pumps protons across the membrane and drives ATP production (which is relied on by cells for fuel). This sudden surge in energy is what scientists think is nudging hair follicles out of their resting state and into the active growth phase of the hair cycle, known as anagen.
While this is a popular theory, researchers have also proposed many alternate mechanisms beyond ATP production. For example, increased blood flow due to the release of nitric oxide or even a reduction in scalp inflammation. Its worth noting that in the 5 decades that this topic has been actively researched, researchers are still not entirely sure at the true cause of this phenomenon, though the research has been substantial enough that LLLT devices have been cleared by agencies such as the U.S. Food and Drug Administration.
Which Wavelengths of Light Show the Most Promise?
The Lanzafame Trials (2014 & 2017) published in Lasers in Surgery and Medicine and Dermatologic Surgery were trials done with 655 nm red light. The 2014 trials on men showed a 37% average increase in hair growth while the 2017 trials on woman showed a 51% increase. This aligns with other research showing that the optimal window for the treatment of hair with light ranges between around 600 to 1000 nanometers. Wavelengths that fall between this range are generally strong enough to penetrate the scalp deeply enough to reach the follicle while being efficiently absorbed by cytochrome c oxidase, which is believed to drive the effect. Currently, two modalities dominate the market: Low-level laser devices use single wavelength light while LED devices, which are cheaper to produce have become common in helmets in home use. Both modalities aim to deliver the required dose of red or near-infrared light to the scalp. Trials at this time have not concluded which method is clearly "better" than the other.
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