Red light therapy, also known as photobiomodulation, has shown promise in various medical applications, ranging from promoting wound healing and reducing inflammation to enhancing nerve cell regeneration. A crucial factor in achieving the desired therapeutic outcomes is the accurate dosing of light energy. This article will explore the importance of dosing in light therapy and present five influential research papers that have shaped our understanding of this topic.
What is dosing in red light therapy?
Dosing in light therapy refers to the amount of light energy delivered to the target tissue, typically measured in joules per square centimeter (J/cm²). The optimal dosing varies depending on the specific condition being treated, the wavelength of light used, how you use a device, and the individual's unique physiology.
In the video below, Aaron Rogers discusses all things Red Light Therapy with Bart Wolbers. The vide below is embedded from the section where they talk about dosing.
Why Dosing is Key to Effective Light Therapy
Here are some of the key reasons why dosing is critical to effective light therapy.
Biphasic dose response:
Many biological processes, including the response to light therapy, follow a biphasic dose-response curve, meaning that both too little and too much light energy can be ineffective or even harmful. Optimal dosing is essential to achieve the desired therapeutic effect without causing adverse side effects.
Lately, experts in the field, such as Prof. Dr. Michael Hamblin, have questioned the nature of the biphasic dose response - at least in humans. The response exists but is likely different than in animal studies where it’s well validated. You can read about Prof. Dr. Hamblin’s comments in the PBM 2024 writeup, where Kineon was also present.
Penetration depth:
The depth at which light penetrates the tissue is dependent on the wavelength, the way you use a red light therapy device, and dosing. Accurate dosing ensures that the appropriate amount of light energy reaches the target tissue without being absorbed by superficial layers or overexposing (hot-spotting) the surrounding tissues. Using multiple treatment modules that can be placed around the target tissue is a great way to reduce this issue.
Specialized devices such as the Kineon MOVE+ are placed directly on the skin for increased penetration. A device that makes skin contact reaches greater penetration than a device that doesn’t. And, when mechanical pressure is applied - as you can with the MOVE+ by tightening the straps - the light penetrates even deeper. Applying that mechanical pressure is called the “contact method”
Also, because the MOVE+ contains lasers that emit the light in a straight line into the tissue, penetration increases as well. Simply put, LEDs often have a wider beam angle so that the light is not projected in a straight line but in an area that looks like a cone. Because it contains lasers, the MOVE+ therefore achieves better penetration than with just LEDs, for spot treatment.
Scientific validation
In “photobiomodulation” or red light therapy, there are many unknowns. Even though there have been around 10,000 studies published on the topic, there’s lots that we don’t know yet. Fortunately, we do know some things: the current published literature on specific topics that can guide our dosing protocols.
For instance, there are many studies that have established protocols - with power outputs, wavelengths, and so forth - in the red light therapy for osteoarthritis domain. We know these protocols work for most people because studies have shown the average outcome across individuals. Those study outcomes have subsequently informed the way we created the Kineon MOVE+, so that you’re getting a very predictable result.
The same is true for our HEAL+, a product for gut health we’ve launched on Indiegogo right now. The dosing protocol for the HEAL+ is derived from the published red light therapy literature as well as our in-house testing. That way you know that you’ve got the highest probability of success with a device because we didn’t make these dosing numbers up–the dosing numbers stem from the published literature.
Individual variability:
Each person's physiology is unique, and factors such as skin pigmentation, tissue density, and metabolic rate can affect how light energy is absorbed and utilized by the body. Accurate dosing accounts for these individual differences, ensuring that each person receives the optimal therapeutic effect.
Let’s explain why individual variability matters with regard to red light therapy dosing. Right now, it’s impossible to give a simple formula that’s universally true that offers optimal dosing to each individual.
Why?
The human body is a complex system with many interacting parts and many variables - both discovered and likely undiscovered - that affect dosing. An example of a simple formula would be Newton’s Laws of Motion to predict the movement of a cannonball that you drop from a tower. If you know the initial conditions, you can more or less predict how fast and where the cannonball ends up on the ground.
With complex systems - such as the human body, the weather the next day, economic models, or traffic in a city - there are so many moving parts that you cannot predict the outcome with a simple formula. Also, changing one variable will influence the way other variables interact with each other.
Red light therapy dosing is the same. And, with that topic of individual variability, let’s move on to the practical implications that this has for your dosing strategies:
Best Practices for Dosing in Light Therapy
In this section, we’ll talk about the best practices for red light therapy dosing:
Dealing With Individual Variability
So, we’ve just concluded that there’s individual variability with dosing. Hence not everyone responds the same way. So if you’ve got a particular device that you apply for a certain amount of time, in a specific way, for a specific duration, two individuals may respond differently to that application.
Individual variability isn’t a bad thing–it’s just a fact you’ll have to deal with. In the same way people can respond differently to a low-carb diet, or to strength training or aerobic exercise, individuals also respond differently to light.
Some people are hypersensitive to light, for instance. These people often cover up with clothes in the sun and wear sunglasses outside. We’ve heard from people who cannot even see outdoors on a bright sunny day, without sunglasses.
If you’re hypersensitive to light, you may want to take things slowly with light exposure. Ideally, you’ll monitor yourself closely during that process. And, the easiest way to monitor yourself is to go by how you feel after a red light therapy session.
For instance, if you use the Kineon MOVE+ as prescribed by the instructions for knee pain and your pain increases, you’ll have to change your protocol. In that case, you could start trying to halve your exposure time and then monitor how you’re doing. For many people who don’t get any results with red light therapy, the results eventually come after some trial and error.
Just like one person will do well on a low-carb diet and another may not, you may also do well on more or less light exposure. Dosing guidelines are just that: guidelines–and not absolutes. Of course, we’d love to discover a super simple formula that universally works for dosing for each and every individual on this planet. But unfortunately, that’s not the case right now.
Nevertheless, you’ll want to know how to calculate dosing so you can adjust your treatment parameters. That principle is similar to knowing how to calculate your protein, carbohydrate, and fat intake when you’re dieting - knowing what the inputs are, allows you to measure what happens when you change things up.
Calculating A Red Light Therapy Dose
The most common way to calculate a red light therapy dose is to start with the quantity of light that enters your body at any given second in an area. That quantity of light is expressed as mW/cm2. For instance, a lower-powered device may emit 20 mW/cm2 to your skin and a higher-powered device may emit 50 mW/cm2.
Now, you’re exposed to that light over time. So if you apply 20 mW/cm2 at a given area for 1 second, you’ll apply a 120 mW/cm2 dose over 6 seconds. Over 60 seconds, moreover - equalling 1 minute - the dose will be 1,200 mW/cm2. And, over 10 minutes the dose will be 12,000 mW/cm2.
That latter number of 12,000 mW/cm2 can be converted into Joules/cm2 - both are energy measurements. 12,000 mW/cm2 equals 12 Joules/cm2. And it’s the latter denomination that you’ll often see in dosing guidelines.
But let’s give you a few more examples:
Let’s say a device puts out 50 mW/cm2. In one minute, you’ll then get a 50 mW/cm2 * 60s = 3,000 mW/cm2 dose. And 3,000 mW/cm2 equals 3 Joules/cm2 (J/cm2).
Another device may emit 300 mW/cm2. In three minutes, you’ll then get a 300 mW/cm2 * 180s = 54,000 mW/cm2 dose. And 54,000 mW/cm2 equals 54 Joules/cm2 (J/cm2). That 300 mW/cm2 is very powerful but can be used sometimes, such as in laser dentistry for anesthesia.
Common Dosing Guidelines
It’s somewhat widely accepted that for superficial tissues, such as your skin or ligaments that are really superficial on the human body, you’ll need a dose of 2-10 J/cm2.
For deeper tissues, you’ll need a dose of 10-70 J/cm2. Your muscles, most of your circulatory pathways, joints, bones and so forth are all examples of deeper tissues.
In each given day, you’ll have to choose between a superficial treatment and the treatment of deeper tissues. Why? Well, the quantity of light that reaches deeper tissues decreases exponentially. So the deeper you go into the body, the less light will reach there.
Hence, you’ll have to treat an area for a longer period of time or with more intensity to saturate the deeper tissues with an optimal dose. But, once you do so, a lot more light has entered the superficial tissues - these superficial tissues will have received an overdose and not get any benefits.
Monitoring Your Dosing Outcomes
The 2-10 J/cm2 for superficial tissues and 10-70 J/cm2 for deeper tissues is an excellent dosing starting point for most individuals. If you’re in poor health, however, it’s recommended to start slow.
Factors such as poor mitochondrial function, having one or more chronic diseases, fibromyalgia or chronic fatigue, and hypersensitivity to light are reasons to start with perhaps half the dose we suggested above. You then monitor your progress.
If you feel good and benefit from red light therapy, the current dose is working. But, if you get side effects, such as poor energy levels or increased joint pain, you’ll have to lower the dose.
Often also, you won’t get any side effects but the benefits will just go away. For instance, you may feel great applying 50 J/cm2 to a given area. But once you increase the dose to 100 J/cm2, the benefits that you get at the lower dose may go away.
Hopefully, you now see why monitoring the quantity of light that goes into your body is important. Without any calculations, you’re just guessing and it becomes a lot harder to make changes. It’s like trying to budget a household, without exactly knowing how much money is coming in each month.
Factors Affecting Dosing in Light Therapy
Different factors affect red light therapy dosing in different ways. We’ll discuss a few of them below:
Wavelength of light
First of all, light of different wavelengths have different effects. Blue light, for instance, has wavelengths between 400 and 500 nanometers. Green light has wavelengths between 500 and 570 nanometers. A nanometer (nm) is a millionth of a millimeter.
In red light therapy, we mostly use the red and the near-infrared wavelengths. Red light starts at around 620 nm and goes up all the way to 700 nm. And near-infrared starts at 700 nm and ends at 1,400 nm.
Different wavelengths of light have a different effect on the human body. Blue light, for instance, can tell your body it’s daytime when it enters your eye, can work as an antimicrobial in your skin, and may aid fat loss.
Red light, moreover, is really beneficial for wound healing and skin beauty. And near-infrared light shines when it comes to muscle recovery, joint health, athletic performance, inhibiting pain, and more.
We’re slightly oversimplifying here as different wavelengths within the red and near-infrared spectrum can have unique effects. For instance, near-infrared light at around 810 nm (which is more of a range between 805 and 815 nm) can reach better penetration levels than all other wavelengths. And, the near-infrared wavelengths between 1,065 and 1,075 may have unique benefits because of how it interacts with water inside the human body.
Intensity of light
There’s lots of discussion in the area of the intensity of light. Some people in the industry claim that intensity doesn’t lead to deeper penetration - but we’re not 100% sure whether we agree here.
Nevertheless, there is consensus around one topic: higher intensity will lead to shorter treatment times, if you aim for the same dose in Joules/cm2: With a device that emits 50 mW/cm2, you’ll reach a given dose in Joules/cm2 five times quicker than a device that emits 10 mW/cm2.
However, there’s also an unsolved discussion about saturation in tissues. Many experts claim that the body can only take up so much light at any given time. The example that is frequently given here is that of using your oven. When you’re baking potatoes in your oven, for instance, you may use 400 degrees Fahrenheit for 1 hour.
However, if you were to increase the oven’s temperature to 800 degrees Fahrenheit somehow and put the potatoes in for 30 minutes, the result wouldn’t be the same. Your potatoes would be burned.
Many experts in the industry believe that more intensity doesn’t lead to better results, after a certain point. However, some devices have a very high light output, at 500 mW/cm2 and seem to work well for many people. Thus, the discussion around intensity isn’t over yet.
Duration of exposure
As you already know, the duration of the exposure is closely intertwined with the power output in mW/cm2 (the quantity of light the body is exposed to at any given second). The power output in mW/cm2 combined with the exposure time determine the total dose in Joules/cm2.
You can thus get a higher total dose in Joules/cm2 by either 1) increasing the duration of exposure; 2) using a device that’s more powerful in mW/cm2 output.
Distance from the device
The closer a red light therapy device will be to your skin, the higher the amount of mW/cm2 that will enter your body. So, if you use a device at a 12-inch distance from the body compared to 3 inches, the amount of light that reaches the skin will be far lower in the former rather than the latter scenario.
Next up, a special case exists when devices are placed directly against the skin. That case is called the “contact method”. That method is employed by Kineon in the MOVE+ and HEAL+ - both devices are worn directly on the body. The benefit of the contact method is that there’s almost no reflection off the skin, and much more light will enter the body compared to, say, if you had a device emit light at a 1-inch distance even.
With the contact method, deeper penetration is also reached. For the MOVE+ employing the contact method means that you’ll get penetration deeper into the joints. For the HEAL+ it means that more light will affect the gut microbiome.
Frequency of sessions
Generally, one session per day is sufficient for getting great results with red light therapy. A higher frequency is not better here. Just like you won’t necessarily get better results by going to the gym twice or three times per day, the same is true for light therapy - there’s a sweet spot.
With our MOVE+ and HEAL+, we’ve done all we can to help you get the best dosing frequency that works for the greatest number of people. Of course, you may need to readjust based on your unique biological individuality but generally one session per day is recommended, five or six days a week. Some people get better results by not applying red light therapy one day a week, although that’s based on anecdotal evidence.
Conclusion
The research papers presented in this article emphasize the critical role of dosing in achieving the desired therapeutic outcomes with light therapy. An understanding of the biphasic dose-response curve, penetration depth, and individual variability is essential for clinicians and researchers to determine the optimal dosing parameters for specific conditions and applications. As our knowledge of the mechanisms and applications of light therapy continues to expand, accurate dosing will remain a key factor in unlocking the full potential of photobiomodulation for a wide range of medical conditions.
For more on the science and research behind red light therapy, read:
