Before delving into the “nuts and bolts” of Red Light therapy, it would be wise to clarify the different terms surrounding the science. Since the 1960’s, Red Light Therapy has gone under the name LLLT (Low Level Laser Therapy), as well as Cold Laser while more recently PBM(T) (Photobiomodulation Therapy) has come into fashion among scholars and scientists. However, since PBM Photobiomodulation has yet to gather a broad standing and reputation among the general public, we will use the term red light therapy when talking about the science while photobiomodulation (PBM) for describing the Light Emitting Unit (such as PBM Light).

However, it’s important clarify the term PBM and the meaning behind it. PBM consists of three parts;

-Photo which means light

-Bio which means life

-Modulation which means change, inhibition and stimulation.

The convenience of using the term Photobiomodulation is that:

A)-It emphasizes the benefit, treatment process, result rather than light source which includes lasers and LEDs (Light emitting diodes).

The Laser was invented in the 1960’s but in recent years there has been a shift towards Light Emitting Diodes (LED’s). Lasers are still being used in treatment facilities but LED has become a lot more popular because of:

1. LED’s are generally safer for the eyes and more economical/affordable than lasers.
2. Effectiveness -LEDs have the ability to irradiate a larger area of surface-tissue at once and usually combines different wavelengths as opposed to lasers which are mono-chromatic and focused beam.
3. Convenience for home use: User-friendly and portable.

Today, PBM Light is one of the most portable and compact LED’s/red light therapy units on the market.  It combines 630, 660 and 850 nanometers and PBM Light plus combines 660, 850 and 940 nanometers to achieve optimal penetration of the tissue. It charges by high capacity lithium battery and is the size of a flashlight. It has a built-in timer for 5 minutes.

The application of red light therapy and PBM is still debated in scientific circles on how to achieve optimal effectiveness. A large number of parameters such as wavelength, power density, pulse structure, and timing of the applied light vary for each individual treatment and clinical situation.

B) -It really implies the therapeutic window as shown in Arndt Schulz curve which includes too low of energy will have no bio-stimulation effect while too high will be bio-inhibiting. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6091542/.

What’s the proper dosage implied to desired therapeutic response and result according to the Arndt-Schulz curve?

The Biphasic dose response or the Arndt-Schulz curve illustrates the appropriate distribution of red light therapy, considering energy density and dosage on the application area:

One of the key considerations is using the appropriate dose for the treatment application area to have the desired effect.  As a general rule it’s safe to use and has no side effects. Depending on bio-type and clinical situation, the therapeutic window varies. The PBM Light delivers approximately close to 4 Joule energy for each 5 minute treatment circle.  

As a rule of thumb: Treatment at applied lower dose (4J) is appropriate for superficial tissues such as skin, mucosa and lymphatic system. While treatment at applied higher dose (8J) for structures such as larger and deeper tissue and chronic situations such as muscles and joints for treatment twice a day might take weeks or a month. Acute situations recover quicker, maybe in the course of a few days. The main purpose of red light therapy is for analgesic, anti-inflammatory, wound-healing and tissue-regeneration. It’s a great modality compared to conventional medicine because while conventional medicine has more specific formula and dosage, red light therapy has a lot of room for individual adaptation; doesn’t have a set recipe, doesn’t have any side effects and is safe to use.

Sources:

"The Nuts and Bolts of Low Level Laser (Light) Therapy". Chung, Dai, Sharma, Huang, Carrol, Hamblin. Ann Biomed Eng. 2012 Feb; 40(2): 516-533. 

"Photobiomodulation: Lasers vs Light Emitting Diodes?". Heiskanen and Hamblin. Photochem Photobiol Sci. 2018 Aug 8; 17(8): 1003-1017.