Photonic Red Light Therapy, or PRLT, is a relatively new modality with some amazing properties. Its benefits were initially discovered by NASA while they were trying to grow plants in space and its use has grown from there.
What is PRLT?
As the name suggests, PRLT is a modality which involves the application of red light to the body. A specific type of red light is used, LED bulbs that emit wavelengths at approximately 660nm are ideal. It has been found that light around 660 nm is most effective for therapeutic purposes as it is most easily absorbed by body cells.
How does it work ? After all, isn’t it just red light ?
The short form of PRLT action is that as the light contacts the skin, it fragments, and causes 
molecules to release electrons. This creates a small negative charge and causes the pH to become slightly more alkaline. The change in charge allows PRLT to be used to stimulate acupoints and also reduces pain, as acid equals pain.
For those of you interested in the longer version, the science of PRLT is as follows. When PRLT is applied, the wavelengths of light come into contact with the skin. This contact slows the wavelengths down and scatters the light particles, now known as photons. The photons decay into electrons via the photoelectric effect described by physicists Max Planck and Albert Einstein and thus, as mentioned above, creates a small measurable negative charge and causes the pH to become slightly more alkaline. The body cells function best when they are more negatively charged and alkaline on the inside. Therefore the slight charge and alkalinity created by the PRLT stimulates the cells membrane to draw in nutrients whilst simultaneously expelling wastes. This process excites the mitochondria, which then produce more ATP, or adenosine triphosphate, the energy molecule of choice for the body.
We all understand that the nervous system is a main way of communication for the body, however there is another system of communication called the intraneural collagen matrix, connective tissue, extracellular matrix, or fascia. This tissue is mostly made up of a specific type 
of collagen, and surrounds as well as permeates every single cell in the body. Any time this tissue has a type of energy applied to it (temperature, pressure, movement), it distorts and creates an electrical message which can then by transmitted anywhere in the body. This system tends to be one of defense and repair, responding to pain, illness and disease by initiating healing.
The photoelectric effect of Red Light also stimulates the intraneural system, causing the body to release its own natural healing chemicals. A few others benefits include facilitation of protein synthesis, increased microcirculation flow, and increased cell growth. In fact, Biologists at the Medical College of Wisconsin have shown that cells exposed to Red Light grow 150 to 200% faster than a control group of cells not exposed to Red Light! All of these effects essentially combine to produce healing within the body.
PRLT vs Other Light Therapies
The red light that is used for PRLT is a single color, differing from lasers which use compressed white light. This makes a Red Light much safer to use than a laser, meaning that a lay person is able to use a Red Light without the risk of causing harm. PRLT also differs from infrared light in that it is visible and does not produce heat. An infrared light is only visible when a colored lens is placed over it, and it will get quite warm. The heat prevents an infrared light from being held on the skin, therefore a practitioner is unable to use it to stimulate acupoints effectively.
How is PRLT used?
Based on the above information, PRLT can be used in a fairly general manner. This may include working directly on a trauma, wound, or area of soreness to reduce pain and speed up the 
healing process. One of the greatest advantages of PRLT is that it can be applied to an injury right after it happens as you are not applying any pressure to injured tissues; instead, you are further stimulating the bodys own natural healing processes.
PRLT can also be used more specifically, combining it with Traditional Chinese Medicine and used to stimulate acupoints. Acupoints are areas on the skin which have a lowered electrical resistance and have a measurable slightly positive charge. A positive charge means a more acidic pH and increased pain sensitivity. Due to the fact that applying PRLT creates a slightly negative charge and decreased pH, it’s application to an acupoint will stimulate it. This means that a practitioner using PRLT can influence a very broad range of imbalances in the body. For example, you can work on a set of points geared towards improving overall health or you can use specific points that may aid in digestion, help boost the lymphatic system or support a particular joint. The advantage to using a red light to stimulate the acupoints is that it is non-invasive (you don’t have to puncture the skin with a needle) and it works much more quickly than stimulating the point with acupressure, needing only 6-10 seconds instead of a minute or two.
At any time using PRLT on a horse, the practitioner needs to be very aware of the horses response to the light. While some horses may be initially unsure of what the practitioner is 
doing, it doesn’t take long for most horses to relax. Horses that are familiar with the light may start to relax as soon as they see the light, or they may even present body parts that they would like the light applied to! If the horse releases by licking and chewing, it is time to take the light off of that particular area. If using PRLT on a wound and the horse keeps moving away, the area has had enough stimulation for the time being and the horses innate ability to sense what it needs should be trusted. Forcing the issue may lead to the horse being unwilling to have PRLT applied in the future.
PRLT is a great modality and can be used alone or along with other techniques. The best part is it can have so many benefits, but there are no known negatives.
References:
http://www.jent-equine.com.au
http://missionignition.net/bms/led_heal.php
Equine Photonic Red Light Therapy,?? Certification Course Manual 2013, Dianne Jenkins