Everything You Need To Know About Red Light Therapy Dosing

In this blog post, I'll talk about dosing your red light therapy sessions.

At this website, we get tons of questions about optimally dosing red light therapy for different goals, ranging from aiding with skin disorders, reducing pain or symptoms of fibromyalgia, speeding up recovery, enhancing your beauty, and everything in between.

This blog post gives you rough guidelines for many of such purposes, even though, it will also become evident that dosing your red light therapy sessions isn't guided by hard science (yet). 

As will become clear, many variables affect what is considered an optimal dose within red light therapy, and there's even debate on how to dose properly for more superficial or deeper tissues.

I've divided this blog post into several sections:

Ready?

Here we go: 

 

 

The Basics Of The Optimal Red Light Therapy Dosage: Superficial And Deeper Tissues

Getting the dosage right on red light therapy is absolutely essential. Many studies actually find no results from red light therapy when using the wrong dose (or light frequencies).[9; 10]

That outcome should not come as a surprise.

An analogy with exercise is great to understand this principle: if you use an exercise intensity that's too low or too high, you won't get the results you're aiming at. The same is true for red light therapy.

At the most basic level, just one thing matters for achieving the right dosage: the amount of "Joules" of red and infrared light hit that your skin over time.

Sounds complicated? Let's dissect that sentence...

What are "Joules"?

Joules are a unit of energy. For almost all treatments, we want an intensity between 3 and 60 Joules per square centimeter (cm2) of your skin. 

The higher the Joule value, the more light energy you're thus adding to (a specific part of) your body.

Knowing your Joule input takes some effort. You generally have to do some calculations to arrive at that Joule value.

Most red light devices supply you with a milliwatt per square centimeter (mW/cm2) dosage of light.

In general, the milliwatts per second you're exposed to increases when you get closer to a red light therapy LED panel and decreases the farther removed you're from a red light therapy device. 

That milliwatt per square centimeter number can be used to calculate a Joule value. For every 1,000 mW/cm2 added to your body, 1 Joule (per cm2) is added.

Let me give an example:

A red light therapy device might add 20 milliwatts per square centimeter per second, or alternatively, 100 milliwatts per square centimeter (per second). In the first case, it takes 50 seconds to add 1 Joule of energy to your body--in the latter case, it only takes 10 seconds.

Let me give you a simple analogy to understand red light therapy dosing:

Knowing how many Joules (per square centimeter) is like knowing the weights you're using in the gym: if you use three times as much weight, the effect will be very different.

Let's do some calculations to better understand the concept of "Joules":

  1. Let's say you want to put 50 Joule of energy into your body. Your red light device puts out 100 mW/cm2 per second at a 50-centimeter distance. 

    Every minute you use the device would add 60 seconds * 100 mW/cm2 = 6.000 mW/cm2 = 6 Joules of energy (per square cm2) to your body. 

    When rounded-off, you need to use your red light therapy device for about 8 minutes to get a dosage of 48 Joules.

  2. Let's say you want to put 20 Joules (per cm2) of energy into your body. Your red light device puts out 10 mW/cm2 per second, at a 100-centimeter distance.

    In one minute, you'll put about 10*60 = 600 mW/cm2 into your body, which equals 0,6 Joules (per cm2). For 20 Joules, you would need 20 / 0,6 J = 33,3 minutes of therapy - which is a long time.

    Solution? 

    Move closer to your device. At a 20 centimeter distance, the device might put out 100 mW/cm2. From that distance, you'll add 6 Joules of energy per minute, which would equal 3,3 minutes of total treatment. 

    The latter case sounds much better right?

  3. Let's say you want to do a skin treatment, and need to put 5 Joules of total energy into your body. The skin is a very superficial organ and does not need very high dosages. 

    Assume that you've got a big light panel that puts out lots of light.

    You're standing at a 30-centimeter distance, and you're thinking: "10 minutes ought to be enough to get great results!"

    Big mistake...

    Let's calculate:

    At a 30 centimeter distance (~12 inches), the light output is 90 mW/cm2. That distance and light output combination equal 5.400 mW/cm2 or 5,4 Joule per minute. If you're using your device for 10 minutes, you're adding a total of 54 Joules of energy to your body, which is more than ten times the amount of energy you needed for skin treatment (5 Joules).

    Big mistake! 

    You're using the red light therapy panel totally wrong. With 54 Joules, you're treating your deeper tissues, while not getting an effect in your skin at all.

I cannot repeat that principle often enough: you need the right dosage for any specific goal you may have.[1; 3; 77; 144; 210; 281; 282; 283; 284; 285; 286; 287]

To know what you're doing, you need to calculate the dosage. 

Fortunately, many companies nowadays do supply a dosage guideline with their product, so that you don't need to go through these calculations manually. The bad thing is, however, that mots of these calculations are wrong - something I'll explore in the next section!

Sometimes, companies offer a simple app to calculate the dosage - which is a great development, although, usually imperfect.

I've decided to include this section anyway because you might not have such a manual, or you might have a light setup where you combine several red light therapy panels.

Let's now look at how to treat different tissues...

Even though that topic of dosage seems complicated, it's really not:

  • More superficial tissues, such as your skin, teeth, or superficial blood vessels, need a low dosage of 3-10 Joules
  • Deeper tissues, which include your muscles, joints, organs, or bones, need between 20 and 60 Joules. Most studies actually stay around the 20-40 J dose, every few days.

Once you go over 80-90 Joules, you generally reduce the overall red light therapy effects. If you surpass 20 Joules, moreover, you'll also decrease the treatment effects for superficial tissues, but increase the effects on deeper tissues (although I'm oversimplifying here, more on this later!)

Oh yeah, one more thing:

This bears repeating: always keep in mind that your red light therapy device is often accompanied with a description of its light output at a very specific distance.

Always take that distance into account. While going off the input of companies isn't perfect, it's better than doing nothing - the perfect is the enemy of the good here.

It's often simplest to follow that direction, at least, if you're using just one panel. 

Again, if you get closer to the device, of course, the mW/cm2 per second will increase, upping the total Joules per cm2 of energy that are added to your body.

 

In terms of dosage, the amount of light you need can vary from person to person. The maximum dosage of 60 Joules per square centimeter is not set in stone for everyone.

Why?

You may remember that I've treated the concept of "hormesis" in a previous blog post on stress. Hormesis entailed that the right intensity of a biological stressor could make your body stronger, while either too low or too high of a stimulus has adverse effects.

If you're in poor overall health, using red light therapy might mean that you would need a lower overall dosage, to begin with. 

While I've just given a maximum dosage of 60 Joules, if you've got a disease such as fibromyalgia or Alzheimer's, you'd want to start off with a much lower dosage. After testing a low dosage, watch how your body reacts. If treatments are successful, you may be able to increase your dosage over time. 

The same principle applies to other "hormetic stressors" I've talked about before, such as cold therapy.

If you've read my cold article, you'll remember that I'm recommending people easing very slowly into cold therapy. Just as too much intense exercise makes you more tired, and too much cold therapy makes you more tired (or worse: gives you frostbite or hypothermia), red light therapy has the same effect.

I personally know people who have chronic pain or fibromyalgia who are wiped out by doing too much red light therapy!

That's all you need to know?

No, not yet...

There's another important issue with dosing though: the overall strength of the light output.[7; 282; 306; 307; 308; 313; 314]

Yes, really.

At the first sight, you might think that using a red light therapy device for longer periods of time will have the exact same effects as a larger device for a short period of time.

But that's not true...

Many studies actually show that there's a certain threshold of light output that needs to reach your skin to reap all the benefits. If the light is too weak, you won't get the full benefits of red light therapy for deeper tissues.

An often-cited minimal power density to reach deeper tissues is 50mW/cm2 to 100mW/cm2.

If you've got a weak device, you cannot reach and thus treat these deeper tissues. For that reason, I will not recommend any of the weaker red light therapy LED panels in my next section that contain specific recommendations.

Don't get me wrong: a lower wattage is fine for treating more superficial tissues, but you need stronger exposure when you want to treat your bones, organs, or cartilage. You're often cutting yourself short by buying smaller red light therapy devices.

Oh yeah, by the way, there's another reason not get too close to red light therapy panels:

Many red light devices put out some "electromagnetic frequencies", which can be harmful to your health, especially when the source of the exposure is very close to your body. 

Stay away at least 3 inches (~7 centimeters) to avoid that radiation. It's not safe to put most red light therapy devices directly on your skin, if you don't know the exposure levels!

Lastly, even though you can do multiple red light therapy sessions per day, I would not exceed 60 Joules per cm2 each day. Staying closer to 40 J is probably even better.

That recommendation entails you can do two treatments of 20 Joules per day or one treatment of 40 Joules per day. 

I would also lower the overall dosage if you're spending lots of time in the sun.

Why? 

There's no need for a 60 Joule dosage if you've spent 3 hours in the sun. If you're spending that much time in the sun, it's better to use a 5-10 Joule treatment to optimize your skin condition. 

The good thing? You now know about the basics of dosing red light therapy. The bad news? Things are more complicated than the basic calculations I've just carried out above - here's why:

 

 

Complication: How LED Panels Are Very Different From A Dosing Perspective Than Laser-Studies

So far, so good, right?

Well, maybe!

Here's where the narrative becomes more complicated! The circumstances I previously described are idealized circumstances. In reality, many other factors play a role, such as light's reflection off the skin, and differences between testing equipment, and more.

The argument I'm listing below is mostly a summary of what Andrew LaTour has already developed on his Gemba Red blog.

Here are some links to excellent reading material on properly dosing red light therapy:

 

Andrew's findings?

Well, many studies use lasers or specifically-designed LEDs that are placed directly against the skin during treatment. The benefit of that methodology is that the amount of red and infrared light reflecting off the skin is minimized.

The LED panels you buy online nowadays, are not used directly against the skin, usually, and therefore the dose calculation becomes different.

So using 50 mW/cm2 directly against the skin, OR, a much higher power output that translates to 50 mW/cm2 from a 15-centimeter distance, has different physiological effects.

In the first instance, light cannot reflect off the skin because the source of the light is placed directly against the skin. In the second instance, at least some of the light is lost due to reflection. 

Due to that difference, it's logical to assume that you need higher dosing in the second instance to achieve the same physiological effect. 

My personal experience accords to that picture: I'm having better results using my BioMAX 900 from a 2-3-inch distance, for shorter periods of time, than the commonly prescribed 6-12-inch distance.

Simply put, red and infrared light reflected off the skin is an important variable in the dosing dynamic. That variable has not been fleshed-out perfectly because most studies don't actually use the LED panels that are sold by different red light therapy companies today.

Having said that, standing directly against the panel isn't a solution either because you'll massively increase your non-native EMF exposure. For that reason, Alex has carried out an extensive review of red light therapy panels and graded them on their EMF emissions. I highly recommend choosing a panel that has low EMF emissions because you'll want to use them from up close to attain a good effect.

The bottom line is this: even though a company might claim 100 mW/cm2, the net dose that reaches the surface below the skin might actually be lower, much lower. 

That particular reason explains why I have better results standing closer to a panel than from a 6 to 12-inch distance.

In one of his great articles, Andrew LaTour states that:

"Some researchers assume white skin will reflect around 90 to 95% of red and near-infrared light! This is very significant amount! Another research paper cites that only 10-12% of light irradiance is absorbed in skin models." 

(I edited out sources for readability purposes)

As a result, whenever you see a company promoting red light therapy with pictures of people using the device from 1-2 meters away, doing yoga, that picture can be concluded to be very misleading.

You almost certainly need to be very close to a red light therapy panel in order for that panel to work - any suggestion otherwise is deceptive.

Next, there's the issue of inaccurate measurements. Some meters, such as solar power meters, consistently overestimate mW/cm2 delivered by red and infrared light.

So, in reality, the wattage provided by many red light therapy manufacturers will be an overestimation. Translated to your situation, if you're using such LED panels, it means that you're more prone to be underdosing your sessions rather than overdosing.

Hence, even though I've provided you with the 100 mW/cm2 recommendation in the previous section, measurement errors and skin reflection almost certainly ensures that you don't just reach half of that, but merely a quarter.

Next, there's the issue that a real 100mW/cm2 dose might have very different effects than 5-50mW/cm2. Andrew LaTour writes once again:

"[L]ower irradiance <50 mW/cm^2 is less likely to induce detrimental effects. 

Irradiance from 5 to 50 mW/cm^2 is generally used for stimulation and healing, while higher irradiances can be more for nerve inhibition and pain relief."

And:

"Intensity does matter, but more isn't always better! Do you cook your turkey low and slow, or set the oven to broil and let it burn on the outside and be frozen on the inside?

There are certainly applications for higher irradiances. We would like to see a distinguishment in Red Light Therapy for a "Recommended Daily Allowance" as opposed to a "Therapeutic Dose". An RDA for light!"

(Slightly edited for readability)

The infrared portion of sunlight reaches about 20-25 mW/cm2, and going (much) higher than that might have detrimental effects.

Fortunately, the reflection of the skin and the over-estimation of the power density of many panels due to measurement methods thus means that the standard "100mW/cm2" is thus closer to the net 25 mW/cm2 that works best.

The best part? The conclusion of this section! By accident, you probably get the right dose from an intense LED panel that is optimal. So no need to excessively worry about 100 mW/cm2.

Even if tons of light reflects off your skin and readings overestimate power output on your LED panels, the next dose reaching deeper tissues below your skin is probably pretty good once you get close to your panels.

A panel that can be used close-up - with little EMF - might be just as good as a bigger panel emitting tons of light, because reflection plays less of a role in the former scenario.

Understood?

Let's move on to the next topic: understanding who specifically should use red light therapy:

 

Who Should Use Red Light Therapy? How Variables Such As Sunlight Complicate Dosing

Who should use red light therapy is a very interesting question.

My brutally honest answer is: "almost everyone"

Remember that I mentioned at the beginning of this article that red light therapy can never replace sunlight? That assessment is fully 100% correct. But what red light therapy can positively do for you, is mitigate some (but certainly not all) of the effects of missing sunlight in your life.

Remember that 95%+ of people in life do not get enough sunlight in their daily lives. 

Let's consider why red light therapy can help in these instances:

  • You might be working night shifts, and your three children are dependent on your income. Instead of quitting your job to get more sunlight, you're using red light therapy to mitigate some of the effects during the days that you're working at night and are sleeping during the day.

    Not getting enough light exposure thus causes problems for your health - which red light therapy can (partially) mitigate.

    Sure, night shifts are horrible for your health, increasing your chance for certain cancers, heart disease, obesity, diabetes, autoimmune disease, and more. But not being able to feed your children because you're quitting your job is worse than that.

    Red light therapy can thus offer your body more light when you're working during the night. Make sure to also plan to get a job during which you can get sunlight exposure in the long-run though.

  • Let's say you're a businessman, consultant, or lawyer, and going through 80 hour work weeks. Sure, you might get some sunlight during the weekends (if you're not sleeping from overwork).

    And no: 5 minutes of sunlight when you walk from the parking garage to the office is not enough.

    I'm also pretty convinced that people with these jobs will not quit their jobs to get more sunshine. On the one hand, I get that you're not quitting your job to get more sunshine. On another level, I think it's irrational and self-destructive to prioritize money over health.

    But nevertheless, let's assume (for the sake of argument) that your choice of money over health is correct. 

    In that case, I'd strongly recommend you use red light therapy during the five days you do not have the possibility of getting much sunlight. 

    You'd even get more work done with a red light therapy panel, so it's a no-brainer...

  • Alternatively, you might be getting some sunlight during the day. Let's say you get 15 minutes of sunlight in the morning, and 15 minutes of sunlight on your arms during the afternoon (during your work break). 

    In that case, I would still strongly recommend integrating red light therapy into your life, as that exposure level is nowhere near what ancestral human beings and traditional societies get. 

    You're still having a light shortage by just getting half an hour of sunlight exposure on just a part on your body.

  • Let's say you're of older age, and moreover, cannot walk anymore. Or let's say you're in poor health, or have another reason why you cannot get enough sunlight each day. 

    In all these two cases, make sure you're at least mitigating some of the effects of losing out on sunlight by integrating red light therapy into your life.

Almost everyone should use / will benefit from red light therapy, especially if you've got an indoor or night job.

Yes...

Sadly enough, society is built up in such a way that sunlight exposure becomes impossible. To me, that fact would be somewhat humorous, but only if it were not such a sad tragedy.

Also, lastly, if you prefer more information for using red light therapy for different purposes, I highly recommend leaving your name and e-mail address below - you'll receive a summarizing-PDF with information about what wavelenghts work for different purposes/conditions:

 

Finishing Thoughts: The Science Of Dosing Red Light Isn't Near Perfect Yet!

Hopefully, this blog post has given you some guidelines to dose your red light therapy sessions.

The science on this topic is far from settled, in part, because the current LEDs offered to the market by red light therapy companies have a different biological effect than the lasers used in 90%+ of studies.

Nevertheless, we're not completely helpless - far from that! In fact, it is reasonable to suspect that using the panels the way they are commonly advertised ensures you end up with a 20-25 mW/cm2 dose, even though 100 is communicated to you.

Skin reflection and improper measurement methods are the main reason behind that dynamic of getting less red and infrared light into your body than would normally be expected.

What I hope you get from reading this blog post, however, is that you've now got more insight into the complexity that goes into red light therapy dosing. To properly dose, your panel needs to be tested by a third party, with proper equipment, and reflection of the skin needs to be taken into account. 

Higher dosing is probably not better, but, lower dosing, as is visible on many pictures of people doing yoga 4 yards away from their panel, is certainly not only suboptimal but totally useless!

 

This is a post by Bart Wolbers. Bart finished degrees in Physical Therapy (B), Philosophy (BA and MA), Philosophy of Science and Technology (MS - Cum Laude), and Clinical Health Science (MS), and is currently a health consultant at Alexfergus.com. 

 

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