The color of red has a psychological connection to stopping– stop signs, stop lights, red warning signs and so on. And, it turns out that visible light in the red bandwidth may stop pain to some degree.
The use of red light to reduce pain, inflammation and swelling and to promote wound healing has been known for almost forty years now when a scientist doing a laser experiment on mice discovered that the ones that were irradiated with a red laser grew their hair back faster. But how exactly does red light accomplish this? What are the mechanisms of action? And, can it be dangerous?
I’ll attempt to answer these questions in a way that hopefully makes sense.
When white light travels through a prism, it is dispersed into the colors of the visible electromagnetic spectrum; that is, the component colors that collectively comprise what the human eye perceives as white light. The component colors have wavelengths between about 380 nanometers (1 billionth of a meter long) to about 750 nanometers (nm) and are, from left to right: violet, blue, green, yellow, orange then red.
Just to the left of the visible spectrum is ultraviolet (UV) light and to the right is infrared light (IR); both of which are not visible to the human eye (although some animals can see IR).
While the the therapeutic effects of red light are still being researched, there is evidence that light in this wavelength range (620-750+ nm) can in fact trigger physiological changes in cells, called photobiomodulation that have beneficial effects for injury healing and pain suppression.
The first law of photobiology says that for a low power visible light to have any effect on a living, biological organism the photons (light particles or energy units) must be absorbed by the organism via some type of molecular photo-acceptors, which scientists have given the name chromophores. (Photochem Photobiol. 2002 Aug;76(2):164-70). While the mechanism of action are still being researched, experiments show that human tissue absorbs visible light and undergoes biological changes as a result.
The Plant and Animal Connection
You probably forgot that you were introduced to the phenomenon of photobiomodulation way back in the 3rd grade. Remember in science class when you studied photosynthesis? The name says it all: photo (light) + synthesis (to make something out of other things). Sunlight strikes a plant leaf, gets absorbed by tiny structures in the leaf called chloroplasts which contain chlorophyll (the substance that makes plants green), which creates the energy the plant needs to convert carbon dioxide in the air and water into sugars for its food. Without sunlight, plants would starve to death, and so would every life form that depends on them.
Can it be that mammals have their own version of photosynthesis, or something similar to it? It sure looks that way, considering the tissue healing effects of red light.
How Red Light Influences Cellular Activity
The leading hypothesis of how red light creates photobiomodulation is by increasing cellular energy. Red light gets absorbed by a cell membrane enzyme (a protein) called cytochrome c oxidase, or cox for short. This enzyme influences the electron transport chain, the biological process that occurs in cell mitochondria and determines the rate of ATP (adenosine triphosphate) production and thus available energy in the cell.
Adenosine triphospate is every cell’s “fuel” molecule. Basically, cells trap free energy released from the breakdown (metabolism) of glucose– the basic unit of carbohydrates. The trapped energy is stored in the ATP molecule’s chemical bonds. Mitochondria are the structures in all animal cells where energy is created and can be thought of as the animal version of chloroplasts in plants. The energy released in the bonds of ATP molecules enables the cell to do the things it needs to do, such as repair membranes, remove waste and even multiply.
Another theory on how red light produces beneficial benefits is enhancing gene expression. More ATP production results in more reactive oxygen species production (ROS). In high concentrations this is bad, as excessive ROS can damage tissue and DNA (free radical damage). But with red light therapy ROS production is low level, local to the injury and has beneficial effects. ROS alters the cell’s state of oxidation, or redox state (basically, its electrical charge). Changes in a cell’s redox state induce intracellular signaling pathways such as nucleic acid synthesis, protein synthesis and enzyme activation. This activity then activates changes in transcription factors, which are the substances that up-regulate or down-regulate gene expression. Genes in DNA determine an organism’s physical features and influences its biological processes.
For example, red light activates factors involved in gene expression related to cell proliferation, remodeling, DNA synthesis and repair; ion channel and membrane potential, and cell metabolism. All these processes can benefit wound healing.
Proof of Red Light’s Healing Power
A 2014 Chinese study that involved compressing/ injuring spinal nerves in rats found that LLLT (Low Level Laser Therapy, which uses red and infrared light) “was able to enhance neural regeneration in rats following [the injury] and improve rat ambulatory behavior (ability to crawl and move).” The study’s authors concluded that the therapeutic effects of LLLT in this experiment may be exerted through suppression of the inflammatory response and induction of neuronal repair genes (increased expression of the genes involved in nerve repair). This suggests potential clinical applications for LLLT in the treatment of compression-induced neuronal disorders such as nerve root compression from disc bulges, stenosis and frank injury.
Another study concluded that low-level exposure to 980 nm laser light (near infrared) can accelerate wound healing. Exposure to low- and medium-intensity laser light accelerated cell growth in damaged fibroblast cells, whereas high-intensity light negated the beneficial effects of laser exposure.
So, it appears that the evidence on the therapeutic effects of red light therapy is convincing and the models appear plausible. More research is needed to get a better handle on how to best use light for therapeutic purposes. What we know is that light in the red visible spectrum (620-750 nm wavelength) and infrared (700 – 1000 nm) are preferred because they are better absorbed in human tissue. Shorter wavelengths (blue) scatter and are less absorbed. Red light is believed to be more appropriate for superficial areas (skin surface to a few millimeters below) because the light is quickly absorbed by the red hemoglobin of the blood and carried away; whereas the longer wavelength infrared (IR) and near infrared (NIR) light is appropriate for thick muscles and deeper joints since they are able to penetrate deeper into the body.
Factors that can influence therapeutic effect of red light besides wavelength include power output (watts), frequency, pulse rate, dosage and treatment area. Typical dosages used are 0.5 – 60 Joules/cm2, but there is no consensus among researchers on what constitutes the best dosage for any particular conditions.
Using Red Light Therapy
Red light can be delivered by “cold” lasers (lasers with minimal heat production) or diode (phototherapy) machines. The difference between the two is that lasers produce light of only one wavelength that is collimated (focused and organized), enabling deeper penetration but at a fixed depth and smaller area; whereas a red light diode generates a range of red light in different wavelengths, covering more area and depth levels due to the varying densities of human tissue (skin, fat, muscle, ligament, water).
Medical grade lasers and phototherapy devices can cost a few hundred up to thousands of dollars. These therapy devices can be found in some physical therapy, chiropractic and sports medicine clinics. There are low power, consumer level portable red light and infrared devices that get good results as well. Currently, I am not aware of any studies that compare the effectiveness of the expensive medical lasers with the cheaper consumer devices, but one must realize, light is light! If you have a soft-tissue injury or joint pain, I suggest you try a consumer level red light device before you try the more expensive options. They are available for sale direct to the consumer; no doctor’s prescription needed. So far, the studies indicate that red light therapy is safe to use although it is best to protect your eyes from scattered light during its application by wearing protective lenses.
The red light therapy device I use at home and on patients is the TENDLITE red light therapy device, shown below:
It is simple to use and gets surprisingly good results (and it doesn’t cost an arm and a leg). Use it for TMJ, epicondylitis, trigger points; pain in the hand and wrist joints and anywhere there is musculoskeletal pain and/or inflammation.
Detailed information on how to use the TendLight device can be found in my Amazing Pain Relief Methods ebook.
The Bottom Line: Yes, red light therapy can help heal injuries and lessen pain and is generally safe to use. The best treatment protocols are yet to be discovered, but a good starting point is several sessions of 1-2 minute applications of red light directly over an area of two square centimeters.