The Best Intensity 100 mW/cm^2 for Red Light Therapy: Where is the Data?
Is 100mW/cm^2 the best intensity for Red Light Therapy? Has it even been proven to be safe and effective?
Where are all of the studies for 100mW/cm^2 with full body LED red light therapy?
Medical Devices and Drugs often carry the phrase "safe and effective" when being described. These are two separate aspects that must be examined. A product could be safe, but not very effective. A product could be effective for treating a specific problem, but not very safe in terms of side effects.
100mW/cm^2 is the Best Intensity
Many brands and experts have claimed that 100 mW/cm^2 (milliWatts per centimeter squared) is the best intensity for LED Red Light Therapy. Even more have implied that 100mW/cm^2 is the bare minimum intensity. The best intensities should be even higher like 150mW/cm^2, 170mW/cm^2, 180mW/cm^2 or even over >200mW/cm^2!
However, in accordance with basic advertising law - explicit or implied claims must be supported with evidence.
Given the repetition of many brands and experts, we would expect an abundance of data in the 7,000+ studies on Low Level Light Therapy (LLLT) and Photobiomodulation (PBM) that confirm >100mW/cm^2 is the best for large LED panels.
The added layer of deception is the false claims to be FDA Approved, Medical Grade, or Clinical Grade that also would imply the devices delivering >100mW/cm^2 are indeed safe and effective according to medical authorities.
According to Ari Whitten's book published in 2018, Ari Whitten recommends large LED panels with the ideal intensity of 100mW/cm^2 at 6 inches away.  He also implies that intensities less than 30mW/cm^2 are insufficient.  Just check page 181 in his book if you have it.
Ari Whitten does not actually cite any relevant scientific references as to why exactly 100mW/cm^2 is so effective with full-body non-contact LED light therapy. At best there are some rhetorical arguments about getting short dosing time and getting enough penetration.
Previous sections of the book were well referenced, yet this section on intensity and dosing is conspicuously lacking in relevant credible references. It seemed these intensity recommendations conveniently matched the advertised intensity from his affiliated brands.
In a YouTube interview after the book was published; Dr. Hamblin tells Ari Whitten that between 10-20 mW/cm^2 of intensity is "high" for full-body red light therapy.
This should have been fairly shocking that Dr. Hamblin debunked Ari Whitten's own book recommendations. It completely contradicts Ari's claim that you need "at least 30mW/cm^2" and is literally 5 to 10 times less intensity than the 100mW/cm^2 that Ari recommends as ideal.
On Page 208, Ari Whitten even discusses the NovoThor pod that has been actually clinically studied (unlike the brands he was recommending) and notes the intensity at that time was publicly thought to be 17mW/cm^2. As is the case for most of the book, Ari Whitten does some rhetorical word salad to explain why this number doesn't match his narrative. Finally settling on the excuse that this lower intensity is more for skincare or systemic benefits. When in reality the NovoThor pod is highly popular for athletic recovery and even has a study for Fibromayalgia and another study on Brain Fog.
So somehow Ari Whitten's book ignores the recommendations from experts like Dr. Hamblin and James Carroll (from NovoThor) by a wide margin which seem to correlate in the 10-20mW/cm^2 range, in favor of intensity numbers that conveniently align with his affiliated brands. Even going so far to falsely disparage the NovoThor intensity to help Ari's sales narrative.
Real Data on Full-Body LED Red Light Therapy Studies
All of the studies on full-body red light therapy use less than 50mW/cm^2 as we have collected all of them in a previous blog.
Where the most prominent intensities used for full-body red light therapy is between 24-28 mW/cm^2 in half of the clinical trials using the NovoThor LED bed. 
Much higher intensities (>50mW/cm^2) have not been clinically tested on humans to be safe and effective in the context of full-body LED red light therapy. Despite all the companies lying that their >100mW/cm^2 device is medical grade or clinical grade or FDA Approved.
Extrapolations of the science to assume "more power is better", "higher doses are better", and "higher intensity means less exposure time" are inherently pseudoscience. In fact, it is often specifically advised against in the published literature.
"if the power doubled and the time is halved then the same energy is delivered but a different biological response is often observed." 
I enjoy this quote, because of the marketing meme that many brands claimed to be twice the intensity as Joovv. Even if they did deliver twice the intensity as Joovv (they didn't), they have never actually proven it was more effective. These quotes would imply it is not proven to be more effective with higher intensity.
In a 2017 handbook of phototherapy, the chapter on Dosing Parameters (page 42) written by James Carroll of NovoThor notes the following:
"It is argued (by sales and marketing people) that more power means the required "dose" is achieved in less time, and mathematically that is true; however, it has been shown many times that there is a "dose-rate effect" and if the dose is delivered too quickly the beneficial effects are diminished. This is because the intensity (irradiance/power density) is too high." 
The people promoting "higher power is better" are only telling you one thing; they are not an expert. They are a sales and marketing person. This is a common theme in Ari Whitten's book and with most "reviewers" of red light therapy devices.
Essentially, higher intensities could have a negative effect. Either they encourage people to overdose on energy and potential heat effects, or they encourage people to reduce the exposure time which is inherently important for the optimal benefits. As is mentioned in the above quote with the dose-rate effects.
100mW/cm^2 is the Maximum Intensity - not the Optimal Intensity
Ironically the number 100mW/cm^2 is often mentioned directly in the literature, but more as the upper limit of intensity or a heating risk.
In the excellent free-to-read article by Dr. Barolet, Dr.
"Lower irradiance (<50mW/cm2) is less likely to induce skin hyperthermia leading to potential deleterious effects." 
This seems to correspond well with why we normally see intensities less than 50mW/cm^2 in full-body LED light therapy studies as mentioned above.
They go on:
"Moreover, photoinhibitory deleterious effects may occur at higher irradiances. Such a biphasic pattern may explain the reported increase in MMP-1 when the artificial IR-A irradiances are too high (> 100 mW/cm2), inducing skin hyperthermia." 
They clearly state that above 100mW/cm^2 will initiate significant risks to overheating the skin, biphasic dose response, and skin degradation.
In another article by Dr. Barolet, he notes the optimal intensity should mimic sunlight which he estimates as 30-35mW/cm^2 in the Red/NIR range. He specifically calls out that >100mW/cm^2 is associated with photoaging - which obviously would be very concerning for anyone using red light therapy for skincare and potentially overheating their face. Let alone people damaging their skin for the false promise of deeper penetration.
As we already mentioned, the intensity and exposure time is more important than just calculating the dose as J/cm^2. This below quote literally tells us that if you have a device of >100mW/cm^2 then to throw the dosing equations out the window.
"Within a certain range of parameters, perhaps between 1 and
A review of Photobiomodulation for skin health notes the following:
"Phototherapy employs light with wavelengths 390-1,100 nm and can be continous wave or pulsed. In normal circumstances, it uses relatively low fluences (0.04-50J/cm^2) and power densities (<100 mW/cm^2)" 
Again seeming to confirm that it is extremely undesireable for the skin to expose it to >100mW/cm^2.
Another review of Photobiomodulation on the gut-brain benefits has this to summarize the range of intensities typically preferred in the literature. Again confirming the 100mW/cm^2 is the upper limit, and not the ideal.
"Power densities are usually in the region of 10–100 mW/cm^2" 
Another review including LLLT for Orthodontics states the following:
"In general, the power densities used for LLLT are lower than those needed to produce heating of tissue, i.e., less than 100 mW/cm2, depending on wavelength and tissue type (Huang YY et al., 2009)." 
A study on treating diabetic rats showed this concern about using high power densities on humans.
"Although a biphasic dose response in external PBM with low energy density and multiple sessions may be beneficial [10,14], external PBM may be required for multiple sessions with a relatively large power density (75–100 mW/cm2) and may be unsuitable for large animal studies or human trials with large body surfaces compared to rat or mice models [18,19,20]." 
Just appreciate the wording here. That intensities of 75-100mW/cm^2 are called "relatively large power density". Which is to say these are not the "normal" or "typical" power density for benefits, but they are the upper limit relative to the intensities usually desired for studies.
Even a review article about transcranial brain treatment states the following:
"10–70 mW/cm2 is the typical LED irradiance used in the studies [123,203]." 
But most people seem to presume they need tons of intensity to blast their brain cells. But they specifically separate that LED devices (which tend to be larger in coverage area and total energy delivered) have lower intensities than Laser. Which we will address later.
So for both deep treatments like organs and brains, as well as certainly to avoid skin problems - intensities less than 100mW/cm^2 are often recommended when using large LED devices. With ideal intensities we saw in the previous section are usually less than 50mW/cm^2.
It should start to become clear that 100mW/cm^2 is not the best intensity. The evidence points to 100mW/cm^2 being the upper limit of the range for PBM, and carries acute risks for skin damage and risks the biphasic dose response. It certainly has not been promoted as the best intensity in the literature.
Twist - The Solar Power Meter Lie
You likely already know the plot twist. The original brands were false advertising 100mW/cm^2 at 6 inches away all along.
Ari Whitten himself takes measurements with a solar power meter which is an embarrasment not only to himself, but the entire red light therapy industry. He even posts the pictures of the solar power meter measurements on page 157 of the book.
From the picture, we can tell it is a Tenmars TM-206. So we can just use these numbers in our Solar Power Meter Conversion Calculator blog and get the following numbers.
So what were the intensities of these brands in 2018?
Joovv Mini at 6 inches: 36.6 mW/cm^2
PlatinumLED Bio 300 at 6 inches: 42.8 mW/cm^2
Red Rush 360 at 6 inches: 45.3 mW/cm^2
These are likely more realistic estimations of the intensity these products actually delivered back in 2018.
Lets try to ignore the blatant false advertising here. We have already covered that enough.
But try to appreciate the reality of the situation.
- These brands have inadvertently proven that these intensity ranges of 36.6-45.3mW/cm^2 are safe and effective. Tens of thousands of people likely purchased these units and we assume most were satisfied with the performance and benefits.
- If they had actually delivered 100mW/cm^2 at 6 inches, we would have heard a lot more complaints about skin heating and eyestrain. Remember the original Joovv panels were so low intensity they didn't even provide goggles.
- People following Ari Whitten's dosing calculations and treatment times would have gotten less than half the dose they thought. If they were getting benefits despite underdosing with these low intensities, it is more proof that low intensities and low doses are indeed effective. Of course if people were not getting good results from these products and protocols, the underdosing could explain why.
- If we can re-frame our mindset around these realistic numbers - perhaps this range of 36.6-45.3mW/cm^2 is appropriate for these full body non-contact panels. Especially since they are much more in alignment with the science that often recommends being less than 50mW/cm^2 to avoid heating issues and biphasic dose response.
- Perhaps if Ari had measured these panels accurately back in 2018, his narrative would have been to promote 35-45mW/cm^2 as the ideal intensity. Even if with the wrong intentions, it would have accidentally been more appropriate for the science and safety and effectiveness.
Essentially, despite being incompetent companies that measured their medical devices incorrectly, they might have accidentally delivered reasonable intensities to the consumer back in 2018.
New Book, New Choices
It is rumored that Ari Whitten may be publishing an update to his 2018 red light therapy book in the near future.
In it, hopefully there is more accurate intensity measurements for devices.
However, the more interesting narrative to watch is to find what the new "best" intensity will be?
We speculate there would be 3 options for the book's new narrative:
Stay the same with 100mW/cm^2 being the ideal and 30 being the bare minimum. This way to not contradict the previous version of the book, unless Ari can provide some scientific evidence why the intensity recommendations have changed. But since the first narrative barely had any evidence behind it, there won't be any frame of reference to explain why it would change.
- Update it to again to conveniently match the new measurements of the affilated brands. This could simultaneously contradict the original book recommendations as well as hold flimsy scientific evidence. This scenario would only confirm that Ari is not an independant expert, but a salesperson working for the red light panel industry.
- Update it to listen to Dr. Hamblin that directly told Ari that 10-20mW/cm^2 is high, the evidence that most full-body studies used 24-28mW/cm^2, that natural sunlight intensity our skin was designed to draw benefits from is 30-50mW/cm^2 in the Red/NIR range, and it is often advised not to exceed 50mW/cm^2 to stay in the non-thermal range and maximise the optimal dose-rate response.
The 2nd option is going to be the most likely scenario. Of course a clever wordsmith would make any of their recommendations sound like they are based in science. As we can see from the first book effectively brainwashing the industry for 5 years.
Often brands have resorted to cherry-picking Laser studies to support thier LED Panels. Not only are they very different technologes that should be studied separately, but a laser will have very high intensity despite being very low in power. Smaller devices tend to have higher intensities to compensate for the low power. Which is why we are very clear in this blog we are talking about large LED devices like half-body and full-body panels.
The Two Lies:
There has been two big lies that have pervaded the Red Light Therapy industry.
The first lie has been easy to grasp, that companies and "experts" have false advertised their intensity by a wide margin. They often used solar power meters which measure falsely high in the Red/NIR wavelength range.
The second lie is that "100mW/cm^2 is the best intensity" and that "more intensity is better". Which is much more challenging to understand. But hopefully this blog at least plants a seed of doubt to these narratives.
Notice how Joovv still claims a meaningless Optical Irradiance of >100mW/cm^2 on their product pages under the "Tech Specs" dropdown, not even referencing any distance or what exactly this number is anymore.
Notice that Mito Red Light has an asterisk on their misleading intensity claims stating it is based on solar power meter measurements. And their intensity claims range from 105mW/cm^2 to 170mW/cm^2 on the MitoPro series.
Again, the first problem is apparent that these are extremely misleading intensity claims right on the product pages for these brands. The FTC is rather clear that using asterisks, fine print, or supplemental details on other pages are not sufficient especially if the clarification blatantly contradicts a claim that was made. Especially when the average consumer should not be expected to understand the intricacies for optical measurements with solar power meters. These are not valid legal loopholes. Even if they were, we certainly should trust medical device salespeople that are constantly looking for loopholes to manipulate the consumer.
Joovv doesn't even bother to use an asterisk anymore like they used to claim something about "depending on the distance" or "at device surface" in their 2nd generation website. The >100mW/cm^2 is literally just a random number floating there on the product page, not relevant to anything at all. Apparently they think that is some sort of loophole too.
The second problem is more insidious. These companies seem to imply that 100-170mW/cm^2 is safe and effective for large LED panels. Why else would they be advertising it still? Often implying they are affiliated with the FDA to make it seem like these are safe and effecive numbers reviewed by an authority.
They know the consumer has been brainwashed into expecting to see a number bigger than 100 to assure them of the efficacy of their products. Even if it is irrelevant to the devices they deliver or the actual science.
What is the Best Intensity for Red Light Therapy?
We have laid out an argument in this blog that 100mW/cm^2 is the absolute upper limit where heating effects would potentially start to cause damage. Numbers like 170mW/cm^2 would even be strongly cautioned against to avoid.
At some point it is reckless and irresponsible for "experts" and brands to promote numbers like >100mW/cm^2 that have never been tested on humans in full-body red light therapy clinical trials to determine safety and efficacy.
Rather than re-educate the consumer about appropriate intensity ranges, and admit they accidentally measured their devices wrong initially - most brands are continuing to follow the same profitable narrative. A narrative that was reinforced by "independant experts" blogs and books for lucrative affiliate kickbacks.
Of course if brands admit they were ignorant enough to use solar power meters in the first place, and they were malicious enough to manipulate the science to make it seem like these are appropriate numbers, and for years after getting 3rd party data they are still promoting misleading intensity numbers - maybe a few consumers would get the impression that they should never trust these fake experts and brands ever again.
So brands are stongly incentivised to keep increasing the intensity from their LED panels simply to follow the false marketing narratives that "more power is better". They are also strongly incentivised to keep lying about intensity - because fake experts will conveinently ignore the problems and endorse these brands anyway for their affiliate commissions.
Despite knowing that reasonable intensities like 10 to 50 mW/cm^2 being safe and effective for red light therapy - that is not a catchy sales narrative. Listening to the actual researchers and following the evidence of published clinical studies doesn't correspond to increasing sales.
Even if we get more honest, accurate intensity numbers - will the consumer be properly eductated about appropriate intensity ranges for photobiomodulation? Will the consumer be made into guinea pigs with unpredicented high intensity levels from brands that falsely imply they are FDA Approved? Can salespeople ever encourage moderation and scientific evidence over flashy marketing fallacies? Can affiliates pretend to hold integrity when they are knowingly endorsing brands that false advertise?
Whitten, Ari. The Ultimate Guide to Red Light Therapy. 2018 Archangel Ink
Ghigiarelli JJ, Fulop AM, Burke AA, Ferrara AJ, Sell KM, Gonzalez AM, Pelton LM, Zimmerman JA, Coke SG, Marshall DG. The Effects of Whole-Body Photobiomodulation Light-Bed Therapy on Creatine Kinase and Salivary Interleukin-6 in a Sample of Trained Males: A Randomized, Crossover Study. Front Sports Act Living. 2020 Apr 29;2:48. doi: 10.3389/fspor.2020.00048. PMID: 33345040; PMCID: PMC7739664.
Navarro-Ledesma S, Carroll J, González-Muñoz A, Pruimboom L, Burton P. Changes in Circadian Variations in Blood Pressure, Pain Pressure Threshold and the Elasticity of Tissue after a Whole-Body Photobiomodulation Treatment in Patients with Fibromyalgia: A Tripled-Blinded Randomized Clinical Trial. Biomedicines. 2022 Oct 23;10(11):2678. doi: 10.3390/biomedicines10112678. PMID: 36359198.
Navarro-Ledesma S, Carroll J, Burton P, Ana GM. Short-Term Effects of Whole-Body Photobiomodulation on Pain, Quality of Life and Psychological Factors in a Population Suffering from Fibromyalgia: A Triple-Blinded Randomised Clinical Trial. Pain Ther. 2023 Feb;12(1):225-239. doi: 10.1007/s40122-022-00450-5. Epub 2022 Nov 11. PMID: 36369323; PMCID: PMC9845459.
Rentz LE, Bryner RW, Ramadan J, Rezai A, Galster SM. Full-Body Photobiomodulation Therapy Is Associated with Reduced Sleep Durations and Augmented Cardiorespiratory Indicators of Recovery. Sports (Basel). 2022 Jul 31;10(8):119. doi: 10.3390/sports10080119. PMID: 36006085; PMCID: PMC9414854.
Bowen R, Arany PR. Use of either Transcranial or Whole-Body Photobiomodulation Treatments improves COVID-19 Brain Fog. J Biophotonics. 2023 Apr 5:e202200391. doi: 10.1002/jbio.202200391. Epub ahead of print. PMID: 37018063.
Forsey JD, Merrigan JJ, Stone JD, Stephenson MD, Ramadan J, Galster SM, Bryner RW, Hagen JA. Whole-body photobiomodulation improves post-exercise recovery but does not affect performance or physiological response during maximal anaerobic cycling. Lasers Med Sci. 2023 Apr 26;38(1):111. doi: 10.1007/s10103-023-03759-5. PMID: 37099210.