True Medical Grade Red Light Therapy: Skin Contact, Deep Penetration, and Accurate Measurements

True Medical Grade Red Light Therapy: Skin Contact, Deep Penetration, and Accurate Measurements

How do we get the best penetration of red and near-infrared light photons? What is the definition of "true medical grade" red light therapy? Do we just need to pay dues to the FDA, or is it in the proper delivery of light into the body?

Light penetration through the skin is generally discussed as being wavelength dependent. Where longer wavelengths like Near-Infrared (800nm to 1100nm) offer the best penetration, and shorter wavelengths like Red (600-700nm) has relatively shallow penetration for superficial treatment. We dove into this topic more deeply in a previous article here.

However, this perspective ignores the importance of making skin contact during treatment to optimize absorption and penetration.

Many leading researchers and articles have explicitly stated their preference for skin contact treatment with properly measured devices.

This blog we till take another look at new publications and even more sources that talk about contact treatment - such that we can be properly informed when using consumer grade red light panels.

Bias Towards Non-Contact Treatment:

Unfortunately, the new generation of red light therapy “experts” have been biased by non-contact LED panels advertised to be used 6 inches away. They all conveniently overlooked the differences between skin contact and non-contact delivery while they wrote their original books and blogs with their affiliate promotions.

In the peer-reviewed literature, we see the opposite preference. Most studies, clinicians, researchers, and experts like Dr. Hamblin and James Carroll are all biased towards using skin contact with red light therapy devices. And for good reason. 

The reason isn’t just reflection losses, but we can see a common theme that non-contact treatment has significantly less penetration due to how the optics works.

In this blog we will take a deeper look at the non-contact vs contact method treatments in the clinical research. It becomes clear that the researchers aren’t merely talking about reflection and absorption losses, but a massive difference in penetration depth with non-contact treatment.

The goal isn’t to entirely denounce non-contact LED panels (in fact we sell some), but we need to approach them with the proper mindset if we ever want to dose them properly.

What Distance to Use Red Light Panels?

When we first researched this question in the literature, it became clear the question itself is a Catch-22. If you are even asking the question of “what distance to use red light therapy”, you are already contradicting the bulk of the published science.

Just as important as intensity, time, dose, and repetition - researchers understand there is a significant difference between skin contact treatment versus non-contact treatment.

In fact, there is massive debate and inconclusive evidence about the “best” parameters in terms of wavelengths (nm), dose (J/cm^2), or intensity (mW/cm^2) for different conditions.

Astonishingly, the only treatment parameter that is well-settled in the science – is that skin contact is the ideal way to administer red light therapy.

Let’s take a deeper look into these studies and find out the truth about non-contact treatments.

Contact Mode vs Non-Contact Treatments:

Let’s let one author define these terms for us in this quote:

“Treatment may be done with the applicator either in direct contact with the patient or at a distance away from the skin surface. The former is referred to as contact mode of treatment while the latter is the noncontact mode of treatment.” [1]

It goes on:

“Whenever possible, the contact mode of treatment is preferred for the simple reason that the loss of energy is minimal—virtually every photon emanating from the applicator enters the patient’s skin or tissue. This is not the case with the noncontact mode of treatment, in which some of the photons are reflected or refracted from the surface of the skin resulting in loss of energy and diminishing the intended amount of treatment energy.” [1]

This is a big deal that Dr. Chukuka S Enwemeka would directly tell us that skin contact is preferred “whenever possible.” We should understand that with few exceptions, skin contact is the ideal method of treatment.

red light therapy proper dosing contact distance use inches centimeters panel penetration

This is essentially common knowledge to the researchers and clinicians to prefer skin contact treatment whenever possible, but is still a shock to the modern consumer who has been biased towards thinking standing 6 inches away from a fancy retrofitted grow light is the “true medical grade” treatment for Photobiomodulation.

Significantly More Penetration with Contact Method Treatment

It may be impossible to correlate non-contact studies to our commercial LED panels that promote being >6 inches away.

Human biology is much more complex than merely extrapolating conditions completely out of context from one device to another. Especially if that effort is done by ignorant marketers to sell books and products.

For example, one study measured that skin contact delivered 5 times more penetration than non-contact treatment. [2] So, if you absolutely needed to treat the deeper tissue, no extra dosing time or compensation factor could ever help reach the required treatment depth with non-contact treatment.

Another study makes this comment about why they use skin contact treatment:

“The [contact] pressure technique eliminates any power loss due to air gap and reflection from the stratum corneum, physically places the probe head nearer the target tissue, and blanches out the superficial microvasculature, thereby removing a possible absorbing medium to give better penetration and thus deeper absorption of a more clinically viable photon density.” [3]

In a March 2015 article authored by Dr. Hamblin, Dr. de Sousa, Dr. Arany, James Carroll, and Dr. Patthoff (many of the current leading researchers in PBM right now) they had this to say about their bias torwards skin contact treatment. 

"When a light source is applied to the skin in contact mode more light penetrates due two 2 reasons: (a) compression of the tissue reduces optical interference by blood flow; (b) diffuse reflectance by the skin is reduced." [7]

So note how explicitly clear that we aren't just losing absorption of photons to reflection losses, the penetration of light into the skin is impacted as well.

This emphasis cannot be understated that the leading researchers have all come together in agreement on this method of treatment.

Non-Contact Treatment Compensation Factor?

It is not only the reflection losses we need to worry about (which are already significant at about 60% for Caucasian skin), but even the optics for how the light penetrates and diffuses through the skin is completely different for non-contact treatment. Leading to researchers directly telling us about the penetration loss.

So, we cannot simply take the dosing from a Contact Mode study and sloppily add an additional factor to overcompensate just for the reflection losses. Since that would be ignorant of the change in diffusion and penetration.

red light therapy best penetration deepest wavelengths skin contact dosing distance use panels inches cm

 A similar diagram can be found in this blog.

A recent article published November 17th 2022 by Dr. Hamblin was analyzing the potential therapeutic intensity gotten from sunlight.

“Assuming that the spectral range between 600 and 900 nm that penetrates deeply into tissue is 20% of this 50 mW/cm2 value, then we have the same value of 10 mW/cm2 incident on the head” [4]

Notice the careful wording Dr. Hamblin when he says that 20% of the non-contact sunlight "penetrates deeply" in the ideal optical window range of 600-900nm commonly used in PBM. It is not just accounting for reflection losses, but accounting for penetration losses too. So ultimately according to Dr. Hamblin’s recent estimation – about 80% of non-contact treatment intensity will NOT penetrate very deeply.

Dr. Hamblin’s assumption of 20% deep penetration is somewhat in correlation with the study that observed a 5x loss of penetration with non-contact treatment. Since 20% is equal to one fifth (1/5), so it is essentially the same factor calculated a different way. 

While Dr. Hamblin’s estimation that a factor of 80% intensity losses sounds reasonable and plausible, it would need to be thoroughly studied in different contexts to verify.

Could we increase the intensity of non-contact panels by 80% to compensate for the losses? Probably not, since that just would lead to overheating problems and your product would just be a glorified heat lamp.

Could we increase the time or dose? Perhaps, but since the delivery is inherently superficial we wouldn't want to overdose the skin just for a hypothetical correction factor. 

skin contact torch flashlight 660nm red light therapy best penetration

You won't have much doubt if you try skin contact and see the penetration yourself, even with a red wavelength like this picture. Does your hand glow like this when you hold it 6 inches away from a LED panel?

Finding proper dosing for non-contact treatment is entirely its own new set of parameters that need to be discovered through new controlled studies. Not through oversimplified mathematical guesswork or charlatain booksellers making up their own compensation factors.

Reality Check: How Does Non-Contact Full Body LED Therapy Really Work?

A recently published review of PBM in Sports Medicine had some sobering commentary about the repeated failed usages of full-body LED devices in clinical studies.

“Therefore, we consider that whole-body PBMT has as its main limitation the lack of contact with the target tissue, and the optical profile (or focus on different deep tissue) affects substantially the power density in the muscles and the modulation of the mitochondrial activity, and so the effects of the whole clinical trial are corrupted.” [5]

In a recent talk, Dr. Hamblin notes that “full body panels” are more of a systemic (indirect) treatment. This would imply a knowingness that non-contact panels lack the penetration that would be achieved with skin contact, but the overall power at the surface of the skin is giving us at least a systemic benefit.

red light therapy modular LED panels absorption skin reflection oversized waste penetraion

Oversized "modular" panels are designed to benefit the bank accounts of the business, not actually deliver more therapy to the user.

While non-contact treatment with LED panels certainly can be effective– we need to re-frame our biases to understand how it really works. We should appreciate it is more of a superficial and systemic benefit and utilize this new knowledge properly.

LED Panels, Sunlight, and Incandescent Heat Lamps – Not So Different After All

Dr. Hamblin’s reference to the therapeutic potential of sunlight rouses an interesting point.

From another perspective, we could say that Sunlight and the infamous 250W Near-Infrared Heat lamps are also forms of non-contact red light therapy.

The major factor that made so many LLLT and PBM studies special was the penetration depth delivered by skin contact. Otherwise, it would be no different than ambient sunlight or incandescent lights that we are normally exposed to.

This puts LED panels used several inches away on the same level as Sunlight and 250W Heat Lamps in terms of therapeutic value. They all suffer the same reflection and penetration losses.

red light therapy sunlight 250W near infrared heat lamp incandescent bulb intensity non contact absorption

And Sunlight can be utilized for free and Incandescent Heat Lamps can be purchased much cheaper than a big LED panel.

The real differentiating factor and clinical therapeutic advantage of LASERS and LED for all of these years was perhaps the skin contact.

Self-Fulfilling Prophecy - Non-Contact High Intensity LED Panels:

In the unscientific arms race to make "the highest intensity" LED panels for some vaguely defined "value proposition" of dollars to optical watts - most of the current generation of LED panels on the market are indeed unsuitable for contact method treatment.

value red light therapy panels highest intensity dollars watts

The Western mindset of "value" has been heavily manipulated to promote over-consumption and hoarding.(i.e the Value Meal from Fast Food Restaurants)

Could the emphasis on red light device "value" lead to unnecessary overdose of intensity and power with oversized modular panels?

The many brands that paradoxically all claim to be the "highest intensity" as some sort of meaningless marketing fluff are indeed too intense to be used directly on the skin (and too high EMF). Which could lead to unwanted skin overheating or biphasic dose response.

The PBM literature and textbooks are clearly against the notion of "more intensity is better". Which destroys any "dollars-to-watts" value proposition since we should look for effective intensity and not "the highest 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." [8]

So we shouldn't listen to salepeople who use rhetorical arguments that imply "more intensity is better"? That would make us have to ignore the marketing of 99% of the red light therapy panel brands and influencers, including all of the most popular ones. What a shame.

 red light panel highest intensity best 100mW/cm2

However, we want to be very clear that if a device is not made for skin contact then you should listen to the guidelines of the original device manufacturer to make sure you use them safely.


The clinical research is resoundingly clear for this one parameter of Photobiomodulation – using skin contact over non-contact treatment. 

Not only do we suffer reflection losses of an estimated 60%, but perhaps only one fifth (20%) of non-contact intensity are considered to “penetrate deeply”. Which is why the scientists are so biased towards using skin-contact method “whenever possible”,

The benefits of non-contact LED Red light therapy panels is through superficial absorption of a large amount of power which leads to systemic effects. Non-contact LED panels likely don't offer significant direct penetration (regardless of Red or NIR wavelength) despite the marketing otherwise.

red light therapy penetration false advertising scam

False illustrations like this one imprinted a false expectation of penetration depth of non-contact red light therapy panels. This bias has been hard to shake for many "experts" whose first education was by LED panel marketing.

Certainly, many consumers are using non-contact LED panels with great success – although perhaps accidentally with improper perspective of the true science and mechanisms for how it works.

Our blogs are not to denounce any particular type of device or treatment. Indeed, the science does recognize that non-contact therapy is a viable option. There may indeed be cases where non-contact therapy is preferred, especially if the device itself is purposefully designed to be used at a distance.

Life Outside of LED Panels:

Since our blogs highlighting non-contact treatment there has been a resurgence of acceptance for LED torches (flashlights), handheld LED cluster units, flexible pads, and low-EMF LED panels used on the skin.

LED Flexible Pad Red Light Therapy

Nowadays the consumer is aware that these are effective options because of the contact method, despite the overwhelming marketing of the "red light panel" industry claiming you need super high intensity to be effective. 

This has allowed consumers to utilize more options for therapeutic treatment with red light therapy, and ultimately balances out the previous bias that dominated the industry for several years.

Designers of red light therapy devices may opt to make lower intensity, lower EMF products that can be safely used for skin contact - rather than following the echo chamber of nearly identical rebranded non-contact panels with tons of power.

Ultimately cognizant consumers, doctors, and researchers will need to evaluate on a case-by-case basis of when to non-contact treatment and contact method.

The Future for Non-Contact LED Panels

The good news is that a recent study was published that successfully used full-body LED light therapy for fibromyalgia patients! [6]

So, in the near future we will soon get scientific resources to properly dose non-contact full body devices.

However, the LED Panel industry must be ready by offering accurate 3rd party intensity numbers rather than blatantly lying with solar power meters.

As a minumum standard we should match the measurement methods used in clinical studies, utilize professional light measurement laboratories, or follow Dr. Hamblin's advice to discard solar power meters for better optical power meters like thermopile type laser meters.

red light therapy full body novothor pod bed led red near infrared photobiomodulation

The value of the NovoThor is in its effectiveness to deliver the right amount of intensity for a beneficial effect, not having some arbitrary dollars-to-watts or "highest intensity" sales pitch.

For example, the study on fibromyalgia used a full-body LED bed at 28mW/cm^2 which is properly measured by industry leader NovoThor. This would be incompatable with unrealistic  ">100mW/cm^2 at 6 inches away" claims by major manufacturers. If we are to believe the claims by Joovv, MitoRed, and PlatinumLED then they could be delivering 3 to 5 times the intensity that is documented as effective in studies. And the previous quote just told us that you can't just decrease the time to get the same effect with a mathematical calculation of dose due to the dose-rate response.

So if we want even a slim chance to ever properly dose non-contact red light therapy panels, we need to start with accurate measurement techniques.

Industry authorities like the PBM Foundation will easily classify LED Panels as non-medical grade merely because of the false intensity claims. So while the lies about intensity are clearly profitable for scammers, it will hurt the medical acceptance of these devices in the long run. 

The scammers selling LED panels have a clear choice. Cash in on an easy gimmick of "high power is better" and false advertised intensity - or get proper measurements and re-educate the consumer the nuances about realistic intensity exposure.

Essentially, the "true medical grade" photobiomodulation according to the research establishment is 1) Skin Contact and 2) Accurate Power/Intensity Measurements. Both of which are crucial for proper dosing and both of which the mainstream LED Panels are failing.

Is it a "marketing gimmick" when Dr. Hamblin, James Carroll, and other leading researchers state they generally prefer skin contact with properly measured devices? Of course not, only a belligerent scammer would out themselves by making such a claim - especially when they are obviously biased towards promoting brands that lie about intensity.

When we look for value, we want evidence based effectiveness - not just a blinding amount of power for a sales fallacy.

For real dosing information, you can visit this blog to see how we compiled ALL of the published full-body red light therapy studies in one place. These are the most relevant studies so far to help us understand proper dosing of large LED panels (hint, none of them used ">100mW/cm^2 at 6 inches away").

At GembaRed, we will continue to review the published literature and seek relevant studies that inform us how to use red light therapy panels. Rather than fraudulent companies that use irrelevant contact-method laser studies to market their giant non-contact false advertised LED panels.



Enwemeka CS. Intricacies of dose in laser phototherapy for tissue repair and pain relief. Photomed Laser Surg. 2009 Jun;27(3):387-93. doi: 10.1089/pho.2009.2503. PMID: 19473073.

Kampa N, Jitpean S, Seesupa S, Hoisang S. Penetration depth study of 830 nm low-intensity laser therapy on living dog tissue. Vet World. 2020;13(7):1417-1422. doi:10.14202/vetworld.2020.1417-1422


Chiyuki Shiroto, Misako Yodono, Shigeyuki Nakaji, PAIN ATTENUATION WITH DIODE LASER THERAPY: A RETROSPECTIVE STUDY OF THE LONG-TERM LLLT EXPERIENCE IN THE PRIVATE CLINIC ENVIRONMENT, LASER THERAPY, 1998, Volume 10, Issue 1, Pages 33-39, Released on J-STAGE July 16, 2011, Online ISSN 1884-7269, Print ISSN 0898-5901,,


Hamblin MR. Do Biophotons Play Any Role in Transcranial Photobiomodulation of the Brain? Photobiomodul Photomed Laser Surg. 2022 Nov;40(11):731-733. doi: 10.1089/photob.2022.0095. PMID: 36395085.
Ailioaie LM, Litscher G. Photobiomodulation and Sports: Results of a Narrative Review. Life (Basel). 2021 Dec 3;11(12):1339. doi: 10.3390/life11121339. PMID: 34947870; PMCID: PMC8706093.
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.


Hamblin, Michael & Sousa, Marcelo & Arany, Praveen & Carroll, James & Patthoff, Donald. (2015). Low level laser (light) therapy and photobiomodulation: The path forward. Progress in Biomedical Optics and Imaging - Proceedings of SPIE. 9309. 10.1117/12.2084049.


Hamblin, de Sousa, Agrawal. Handbook of Low-Level Laser Therapy. Pan Stanford Publishing Pte. Ltd. (C) 2017