Pulsed Red Light Therapy: What is it good for and where to get it?
Why would you want to pulse red light therapy, and how do you get it? This blog will explore the important aspects you need to know before purchasing a red light panel or photobiomodulation product that features pulsing.
What is pulsing?
Pulsing is typically a rapid "on" and "off" of a device. In contrast, most studies use continuous light therapy, simply meaning the light is "on" for the entire time of the treatment.
The pulse frequency refers to the the interval between the "on" time to the next "on" time. This is measured and communicated in units of Hertz, or Hz.
Hertz is simply the cycles per second.
So if we say 10 Hz, then the light is flashing on and off 10 times per second.
With pulsed red light therapy there is typically a "duty cycle" of 50%. Which means there is an equivalent amount of time in the "on" position and "off" position.
This also informs us that compared to continuous wave, a pulsed light will have an average intensity of half of the continuous.
Watch our YouTube video on pulsing for a demonstration!
Why do pulsing?
There are 3 main reasons people might be interested in adding pulsing to their photobiomodulation technique.
In order of clinical relevance:
1. Reduce tissue heating.
2. Brainwave entrainment.
3. Some special mechanism or benefit.
Number 1 is probably the most studied in clinical studies. Number 2 has the most practical consumer applications especially for brain health. And Number 3 doesn't have much data, but is heavily abused by brands and marketing.
Let's look at them a bit deeper:
1. Reduce tissue heating.
The first benefit of pulsing is probably the most well-studied in clinical literature.
In the origins of red light therapy they were using lasers, but they needed to be low enough power to be safe and not cause tissue heating or burns.
One of the most effective techniques to reduce tissue heating and still get great benefits is by pulsing. The short "off" times can help the tissue cool to thermoregulate and prevent overheating.
Now this technique enables increasing the laser or LED intensity without causing thermal damage.
So the clinical studies will often compare a pulsed light at a higher peak intensity versus a continuous wave light at half the power of the pulsed light.
Is the benefit really the extra peak intensity, or something more with a special mechanism around pulsing? That's what we need to make clear.
2. Brainwave entrainment.
The second benefit of pulsing is to induce brainwave entrainment. We know that our neurons can synchronize with the frequencies lights and sounds around us.
Using frequencies like 10 Hz (for alpha brainwaves) and 40 Hz (for gamma brainwaves) may help the brain synchronize with beneficial brain states.
These brainwave entrainments has implications help with disease states like Parkinson's and Alzheimer's and restoring the brainwaves to a natural order.
This is the easiest to implement with flashing lights to the eyes, or transcranial and intranasal application of red light therapy. For example Vielight has successfully marketed "Alpha" and "Gamma" intranasal and transcranial lights for years.
3. Some special mechanism or benefit.
Now we get into some dubious and poorly substantiated claims. Most companies will cherry-pick results from #1 and make claims that their pulsing is superior for certain applications or benefits. When in reality the pulsing was superior simply because it has higher peak intensity.
Some attempts have been made to understand a unique mechanism for pulsing. Since logically we would understand that certain cellular functions operate at a "cycle" or "pumping" mechanism, so some wordsmiths with a basic understanding of cellular functions can weave a mechanistic explanation about the timing of the pulse will synchronize with the optimal timing of some cellular function. It makes good logic, even if it doesn't have much data to support it.
Now get your red flags ready for when people talk to you about Nogier frequencies. Which supposedly Dr. Nogier in the 1970's selected several frequencies that are multiples of 1.14 Hz which have special healing capabilities for cells. In my research this is only relevant for Nogier's research into auricular therapy (acupuncture for the ears), and was later adopted into laser acupuncture practice. So if someone was sloppily adding Nogier frequencies to a big red light panel, it wouldn't even be relevant to the true Nogier technique anyway, and would just show they are poorly trying to cash in on a gimmick.
Now when we search for the term "Nogier Photobiomodulation" in Pubmed, there are zero results! Indeed when I double-checked on the massive LLLT spreadsheet http://bit.ly/PBM-database - and search with the find function - there was zero hits on the word Nogier.
So stay frosty if any self-proclaimed experts or brands are trying to sell you a pulsed product that offers some EXTRA benefit, then make sure to ask for the real science and read it yourself. Don't settle for some cherry-picked quote that conveniently backs up their claim.
What is the downside to pulsing?
Now even though we might desire 10Hz or 40Hz pulsing for some alleged medical benefits or so, we must exercise caution with pulsed red light panels in how they relate to strobe and flicker induced distress.
Pulsing can be a double-edged sword. We know that tactical flashlights use 8 Hz pulse to disorient assailants. The famous Pokemon incident caused seizures in hundreds of children - which they determined was a 12 Hz flashing of colors and images - particularly responding to deep red. So we must be careful especially in the visible range of strobe-like flashing not to induce seizures or distress.
The IEEE has determined that any flicker at 100% modulation is considered "high risk" for causing health issues - even invisible pulsing all the way up to 3000Hz.
What about Joovv's new pulse feature?
Let's do a case study with Joovv's latest generation panels (3rd generation).
If you notice Joovv's 3rd Generation panels feature a pulsed mode that they call "Recovery+". Of course this is an abuse of #3 above where they are implying some intrinsic benefit to pulsing without much substantiation. However, you can read that the new Joovv panels will ONLY pulse the invisible Near-Infrared LEDs at 10 Hz, not pulsing the visible Red LEDs. Why would that be?
I think this is the most thoughtful feature Joovv has ever implemented, and I postulate they didn't want to create a potential safety issue by pulsing 10 Hz red light at people! This really shows me that after all these years they have finally learned something about safe red light panel design, and maybe they finally listened to all of their customers that complained about flicker through the years.
But of course this detracts from the potential of the new Joovv panels inducing brainwave entrainment. Having 10 Hz flashing of red lights through a panel into the eyes could be a powerful way to induce the Alpha brainwave, but I think they weighed the risks and decided it wasn't worth it.
This tells us a powerful lesson about safety with pulsed red lights, it may be best to avoid pulsed red lights in the eyes to prevent any safety issues.
Update 7/10/21: New Pulsed Study!
This new pulsed light study shows precisely what happens when researchers use pulsing but don't increase the intensity output to compensate for the dosage lost.
The Continuous Wave light delivered 65.8 J/cm^2 of dose while the Pulsed Wave delivered only 21.7 J/cm^2 at 10Hz and 33% duty cycle. Yet both used the same exact intensity of 54.8 mW/cm^2, due to the nature of pulsing the dose was slashed down according to the duty cycle.
The study was looking for modulation of cerebral electrical activity and cerebral blood flow in regards to Alzheimers.
While many Charlatans love to flaunt the benefits of pulsed lights for treating Alzheimers, in this case there was no significant improvement in the pulsed group. In fact, it didn't even perform significantly better than placebo.
Meanwhile the continuous wave light actually induced natural Gamma Waves in the brain! Showing that perhaps we get beneficial brainwave activity even from continuous wave light, and we don't necessarily need to force brain modulations with entrainment.
Another Study: Continuous Light beats Pulsing for Brain application!
Another study compared different intensities and doses of pulsed red light therapy for treating Major Depressive Disorder - obviously a brain-related disorder. 
What they found was ONLY the Low-Dose Continuous Wave group showed statistically significant improvement. While the pulsed groups did not even show any significant improvement over the control group. 
This is important to keep finding that there are indeed many cases where continuous wave is superior to pulsed wave, especially in these cases for the brain where most people falsely assume they need pulsing to treat the brain.
Loss of Penetration and Dose with Pulsing!
In a new blog we go into detail about the penetration depth of Red and Near-Infrared light. Of course, the intensity itself plays a big role in penetration as well.
When we modulate the intensity through pulsing, then several studies noticed that technically you would have a loss of penetration in alignment with the loss of dosage.
Only in the cases where the intensity is dramatically increased for the pulsed mode would offset the loss of penetration, which likely isn't being done with the LED Light Panels that are being marketed for pulsing.
Where to get pulsed light therapy?
So if a company is advertising pulsed red light therapy for some special medical application or benefit, then be wary!
If the pulsing is a designed to mitigate heating or transcranial application for entrainment then that would be practical and acceptable.
But if companies like Joovv are just adding pulsing to their long list of gimmicks and making extra medical claims, then make sure to dig into the science yourself.
My favorite anti-pulse quote comes from a review on PubMed.
"Regarding the pulsing used, there is no information about what it is supposed to do and what the chosen pulse repetition rates would do other than reducing the energy per time. In the review on the possible effects of pulsing in LLLT, Hashmi et al.  conclude: “It was impossible to draw any meaningful correlation between pulse frequency and pathological condition, due to the wide-ranging and disparate data. As for other pulse parameters, these were in general poorly and inconsistently reported.”" 
This should alert you to the skepticism even among clinical researchers around pulsing! No need to buy into the hype!
Once you know the red flags to dodge, and still want to try pulsed red light therapy - then there might be some affordable options!
Companies on Alibaba like Kinreen and SAIDI light often offer pulsed light models. I personally purchased some pulse modules for my high-powered DIY torch, because I wanted to reduce the dramatic heating effect that I experience with it.
We will be doing a review on the new pulsed panel from SAIDI soon! Stay tuned for future blogs.
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Zomorrodi R, Loheswaran G, Pushparaj A, Lim L. Pulsed Near Infrared Transcranial and Intranasal Photobiomodulation Significantly Modulates Neural Oscillations: a pilot exploratory study. Sci Rep. 2019;9(1):6309. Published 2019 Apr 19. doi:10.1038/s41598-019-42693-x
Spera V, Sitnikova T, Ward MJ, Farzam P, Hughes J, Gazecki S, Bui E, Maiello M, De Taboada L, Hamblin MR, Franceschini MA, Cassano P. Pilot Study on Dose-Dependent Effects of Transcranial Photobiomodulation on Brain Electrical Oscillations: A Potential Therapeutic Target in Alzheimer's Disease. J Alzheimers Dis. 2021 Jun 3. doi: 10.3233/JAD-210058. Epub ahead of print. PMID: 34092636.