Natural light profoundly affects our biology, from how well we sleep to brain function and immune response. The ancient Egyptians used sunlight to disinfect and heal chronic wounds and ulcers as early as 5000 BC, making phototherapy one of the oldest healing methods used by humans.
Evidence is now mounting that by delivering specific wavelengths of red and near-infrared laser light to precise areas of the body, it is possible to precisely tune biochemical processes such as mitochondrial function and cell signaling to aid cellular regeneration and healing.
This technique is known as photobiomodification. It was once used exclusively in hospitals and clinics to reduce pain and inflammation or to promote the healing of wounds, deeper tissues and nerves, and to prevent tissue damage. However, photobiomodification has now become highly commercialized, with low-end laser treatment devices developed to allow consumers to harness its powers at home in an attempt to improve the appearance of their skin.
Low level laser therapy devices do not work like the traditional ablative lasers used in the skin treatment industry. Ablative lasers create thermal microtraumas in the epidermis and heat the underlying dermis to stimulate collagen production. Instead, the new devices use laser light at much lower intensities to stimulate the photosensitive molecules involved in the cascade of skin rejuvenation processes.
Laser light can penetrate the skin more than incoherent light because of a phenomenon known as speckle. Whenever light enters a random medium, such as skin, it is scattered and absorbed, with the exact wavelength determining how far it can travel (see diagram below).
But laser light has an additional property called coherence that causes interference, either combining to create a bright patch or canceling out. On skin (and other random media), this interference pattern is random — that’s a speckle. But crucially, where scattered light combines to create spots, it can penetrate deeper into tissue at intensity thresholds sufficient to initiate biochemical cascades. In comparison, non-laser sources do not create spots.
“If you want to restructure the skin, the light has to reach the basal layer, where regeneration takes place with sufficient power,” says Lucy Goff, founder of LYMA, a wellness company that has developed a low-level laser therapy device for home use. use.
In a study published in the Aesthetic Surgery Journal, cosmetic surgeon Graeme Glass, who operates at Qatar’s Sidra Medicine and is LYMA’s Aesthetic Director, says some experimental evidence suggests that laser light is more effective in deeper target tissue , but that more evidence is needed to inform clinical practice.
Various types of evidence have been generated for some time. In 1967, Endre Mester at Semmelweis Medical University in Hungary observed that defocused red laser light could enhance healing in mouse skin. While testing the safety of this light, he noticed first an unexpected acceleration in hair regrowth and later, improved wound healing. However, it took decades to shed more light on its restorative effects.
One challenge is to understand the mechanism behind photobiomodification. One idea is that red laser light can trigger tiny transport currents inside cells that help mix and spread biochemical reactants and nutrients. Another possibility is that near-infrared light triggers a complex cascade of events in mitochondria, the chemical factories inside a cell that produce most of its chemical energy in the form of a molecule called adenosine triphosphate, or ATP. Light is thought to stimulate an enzyme involved in this cascade called cytochrome c oxidase, which speeds up the synthesis of ATP. Glass explains, “Essentially, you’re supercharging the mitochondria to make more ATP, which helps cells regenerate.”
Photobiomodification is also involved in wound healing. One possible mechanism here is that laser light can change the affinity of proteins called transcription factors that help turn specific genes “on” or “off.” “As a result, genes responsible for aging [cell death] and degeneration have been shown to be turned off, and genes involved in cell proliferation, survival, tissue repair and regeneration are turned on,” says Glass.
There is also evidence that photobiomodification can reduce inflammation through a separate pathway. Some trials have shown that low-level laser therapy reduces inflammation in joint pain, possibly by inhibiting COX-2, an enzyme involved in inflammation and pain.
Many people choose low-level laser treatment in hopes of preventing or smoothing wrinkles. “As we age, we gradually lose the natural process of cell renewal,” says Glass.
He believes that photobiomodification affects skin cells called fibroblasts that produce collagen. In these cells, the cascade of events stimulated by the laser light increases gene expression for collagens and the production of polysaccharides. These sugars cause the cell to draw water through osmosis making the skin look firmer and more elastic. In theory, this should reduce the appearance of wrinkles and lines, and some studies seem to support this.
However, more evidence is needed. After hundreds of clinical studies and decades of use, the question is not whether low-level laser therapy has biological effects, but how. In particular, researchers need to better understand the optimal parameters of these laser light sources for different uses.
This is difficult because many trials involve small groups of patients and are often industry-sponsored and therefore not independent. “There is a lot of room for improvement in the quality of the evidence,” says Glass. He believes that well-designed, adequately powered, independent clinical trials will help answer some of the outstanding questions and allow the full potential of this treatment to be realized.
Meanwhile, commercial applications of low-level laser therapy are increasing, with home laser devices such as the LYMA Laser entering the market. Paul Clayton, LYMA’s director of science, recognized the opportunity to build a portable, low-level laser therapy device without the risk of skin damage. “You can use it around your eyes to focus on the crow’s feet, and it’s completely safe,” he says.
In short, low-level laser therapy is here to stay. “Photobiomodification is a real phenomenon,” says Glass. “The challenge is to ex post prove its therapeutic utility.”
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