Recent advances in LED technology for skin rejuvenation are geared towards increasing light penetration to access deeper skin tissue, with an improved outcome for reverse aging. The superior penetrative ability of pulsed photobiomodulation offers a clear method to achieve this advantage and is the main proposition of UK based LED beauty brand, Maysama, but it is not the only approach. Other LED beauty brands are taking a different approach, introducing a deeper wavelength of near infrared light at 1072nm or by switching out LEDs altogether for laser diodes. Let’s take a deeper look at pulsed LED, laser diodes and the 1072nm wavelength to determine which potentially offers the best advantage for skin rejuvenation outcomes.
PULSED LED Light Therapy
As the name suggests, pulsed LED refers to rapidly switching on and off the light source such that the light pulses on and off. Depending on the frequency of the pulse, this may or may not be visible to the naked eye. Pulsing at a relatively low frequency of say between 1 and 50Hz is generally visible but pulsing at a higher frequency of 100Hz or more is generally not visible to individuals. Many pulse light frequencies from 1 to 1400Hz or higher have been studied, with benefits across the board.
Why does pulsed light therapy give superior tissue penetration?
The answer lies in the light delivery system. Delivering light in a pulsed format allows for cooling of skin between light bursts. This means that light can safely be delivered at higher intensity without risk of tissue damage or overheating. Maysama's PRANA LED light therapy mask has an irradiance of 45mw/cm2 - higher than most LED masks on the market. Delivering light at higher intensity in short bursts, may enhance the biological effects at deeper tissue levels, whilst the 'off' periods allow for skin to cool and 'recover' between pulses, keeping the total light energy delivered safely within an optimal dosing window.
Some research studies on pulsed light refer to higher peak power and indicate a beneficial impacts for light penetration. Peak power is a measure of light intensity during the pulse duration. Let's break down the concept of higher peak power without increasing overall energy dosing in the context of pulsed photobiomodulation (PBM) therapy.
Higher Peak Power:
During the brief "on" periods, the intensity or power of the light may be considerably higher compared to a continuous beam of the same average power. Essentially, the peak power refers to the maximum power emitted during each pulse. This means that for short bursts, the light delivered is much more intense.
Without Increasing Overall Energy Dosing:
When using pulsed PBM, the total energy delivered over time is controlled by the duty cycle, which is the proportion of time the light is on. For instance, if the light is on for 50% of the time, we have a 50% duty cycle. Despite double the peak power during the "on" phase, with a 50% duty cycle, the overall amount of energy delivered over a complete cycle (on + off time) remains the same as it would in a continuous treatment.
For example, imagine a 100 mW light that is pulsed to reach a peak power of 200 mW during each "on" pulse, but is on only half the time. The average energy dose will still be 100 mW, because the light is off for the other half of the cycle.
Therapeutic Implication:
This approach allows pulsed photobiomodulation to penetrate deeper and stimulate cells more effectively due to the higher peak intensities while avoiding overheating or overexposure, which can occur if the same high power were delivered continuously. Essentially, pulsing allows the light to be more "aggressive" in bursts but allows cells to rest between pulses, providing biological benefits.
This combination of higher peak power during pulses and a controlled overall dose often results in more effective biological stimulation, making pulsed PBM preferable for certain therapeutic applications like reducing inflammation, stimulating cell growth, and enhancing neuroprotection.
In support of the enhance penetrative capabilities of pulsed LED, Salehpour showed that pulsed LED at 660 and 850nm impacts brain tissue to improve cognitive function. If pulsed LED at 660 and 850nm can reach brain tissue, imagine the improved impact for deeper skin tissue! And in support of the beneficial impact of pulsed LED for skin rejuvenation, a multi-centre study performed in China, with more than 100 participants, looks at a combination therapy of IPL and pulsed NIR and shows that combination therapy gives superior results for skin rejuvenation.
Even more compelling, a comprehensive review by Hashmi in 2010 highlights the role of pulsed photobiomodulation in maximizing the therapeutic benefits. Pulsed treatments consistently showed enhanced effects in promoting cell proliferation and reducing inflammation compared to CW treatments, with pulsing leading to increased ATP production and reduced oxidative stress. Across these studies, pulsed light therapy demonstrated superior effects in promoting cellular repair, neuroprotection, and functional recovery compared to continuous wave treatments.
Pulsed light's advantage comes from its ability to reduce tissue overheating and cellular overstimulation, and potentially provide higher peak power without increasing overall energy dosage, allowing for not just deeper penetration but more effective stimulation of biological processes like mitochondrial ATP production.
Pulsed LED Overcomes Filtering Effects of Melanin
Together with the enhanced penetrative effect of pulsed light, comes the benefit of overcoming the filtering effects of melanin, which makes pulsed LED the better option for melanin-rich skin. The impact of pulsed LED was extensively tested with melanin filters by Brondon in 2009. Brondon’s tests showed cell proliferation was increased in the group treated with pulsed light, indicating that pulsed light is better able to penetrate melanin rich skin. Whilst Brondon tested a range of pulsed light frequencies between 6 to 6000Hz, his research demonstrated that cell proliferation was maximal at 100 Hz.
1072nm LED wavelength
Whilst less well studied than the 810, 830, 833 and 850nm near infrared wavelengths, deep near infrared at 1072nm is gaining interest. This longer wavelength brings with it increased penetrative ability, making it advantageous for targeting deeper tissues, such as muscle and connective tissue, with minimal interference from superficial chromophores like melanin or haemoglobin.
Preliminary studies suggest that 1072 nm may have strong anti-inflammatory effects, which make it ideal for reducing inflammation in deeper tissues and joints, and potentially may also be beneficial for anti-aging applications by stimulating collagen production at deeper skin layers. Like pulsed LED, the longer wavelength of 1072 nm means there is less absorption by melanin, which translates to reduced risk of surface heating or overheating the skin. This characteristic makes it particularly suitable for individuals with darker skin tones or for applications requiring deeper tissue effects without thermal damage.
Laser Diodes
Let’s take a look at Laser diodes as an alternative to LED’s.
Laser diodes are essentially a ‘higher’ quality of bulb than LED, which is generally reflected in the price of the beauty device. Laser diodes provide a coherent and culminated light source, which means that light waves travel in phase and in a highly collimated bean, which provides a more accurate and very precise wavelength. The accuracy of the beam reduces light scattering and helps to improve light penetration. This makes laser diodes more suitable for treatments targeting muscle tissue and deep subcutaneous layers, to treat deep muscle pain, joint inflammation and deeper tissue healing.
By contrast, LED’s provide non-coherent light with a divergent beam, meaning that light spreads out as it leaves the source. LEDs are effective for reaching the epidermis, dermis and superficial subcutaneous fat, making them ideal for skin conditions and superficial tissue applications. This can provide a more uniform light distribution at the skin surface.
Relative to LED, however, due to the coherent light beam, laser diodes give less even distribution of light at the skin surface, so potentially laser diodes can be less effective for treating surface skin issues such as brightening for fairer skins or treatment of acne.
As the price of laser diodes is considerably more than LEDs, Laser Light Therapy Masks tend to be priced higher than a traditional LED Light Therapy Mask. Whilst for some, this may be justified, for those not concerned with deep seated wrinkles, it is questionable whether it would be worth the additional spend. Laser diodes typically have a higher power density compared to LEDs of the same wavelength, which allows them to deliver more light energy to deeper tissue, but due to the coherent light beam, laser diodes give less even distribution of light at the skin surface, so potentially laser diodes can be less effective for treating surface skin issues such as brightening for fairer skins or treatment of acne. For those concerned with surface skin issues like acne and brightening (Fitzpatrick I-III), LED may give an advantage as they provide a more uniform light distribution at the skin surface.
Which is best, pulsed LED, 1072nm or Laser diode?
Whilst there are no direct studies that compare pulsed LED to laser diodes or the 1072nm wavelength, pulsed LED could effectively outperform the longer wavelength of near infrared at 1072nm and non-pulsed laser diode.
Whilst both laser diodes and 1072nm are interesting advances in technology, relative to pulsed LED, the inclusion of laser diode/1072nm wavelength only offer a fraction of the benefits.
Both laser diode and 1072nm both approach LED therapy from the perspective of light penetration, but this is only one aspect which impacts biological response and overall therapeutic outcome! Unlike laser diode and 1072nm wavelength, the benefits of pulsed LED are not restricted to an improvement in light penetration. In this blog we discuss five main benefits of pulsed LED.
Benefits of Pulsed LED
- Pulsing achieves higher peak power, which leads to deeper light penetration, enhanced biological stimulation and improved therapeutic response.
- Pulsing allows for cooling of skin between pulses – particularly useful for darker skins to prevent triggering melanocytes
- Pulsing allows periods of ‘rest’ for cells between pulses, which allows cells to be stimulated multiple times, resulting in better biological response.
- Pulsed PBM mitigates overproduction of ROS, maintaining the light stimulus in the ‘Goldilocks’ zone for optimal biostimulation
For skin rejuvenation this translates to
- upregulation of ATP production
- accelerated cell proliferation
- and increased collagen synthesis
- reduces oxidative stress
- Pulsing forces cells to uptake micronutrients by Transmembrane Convection – which increases the bioavailability of your skincare active ingredients
Let’s take a look at each of these in turn.
Cooling of Skin between Pulses
We have discussed at length the benefit of pulsed LED Therapy for the management of melasma and hyperpigmentation in our blog; https://maysama.com/blogs/news/using-led-therapy-for-treating-melasma
It is known that Fitzpatrick IV-VI skin types are more prone to post-inflammatory hyperpigmentation on account of a high concentration of eumelanin in the epidermis. Many dark skinned individuals have rightly avoided LED therapy because, if use incorrectly, it can potentially make conditions of melasma worse. Data reveals that exposure to continuous LED light therapy, with red (630 to 660nm) can potentially overstimulate melanocytes and trigger melasma or hyperpigmentation.
Here the use of pulse LED can provide an advantage. Not only does the improved light penetration help light energy to bypass the melanin-rich surface, delivering more light energy to deeper layers, the on/off action of the pulse allows for cooling of the skin between pulses, which further reduces the risk surface heating and the overstimulating of melanocytes. Lower frequencies of pulsed LED in particular (less than 50Hz) give greater cooling periods, reducing the risk of overheating and melanin overproduction.
Cells need periods of rest
As discussed by Hashmi, the logic in favour of pulsed light is that cells may need periods of rest, without which they can no longer be stimulated further.
Cellular stress adaptation is often noted as a benefit of pulsed light, helping cells to more efficiently utilize energy, especially in conditions requiring longer-term treatment.
One mechanism of action of pulsed light therapy on a cellular level is the photodissociation of Nitric Oxide [NO] from Cytochrome C oxidase [CCO], the fourth enzyme in the electron transport chain. Nitric oxide inhibits the action of CCO, which will slow down the production of ATP from mitochondrial respiration. LED therapy release inhibitory NO, which can then increase electron transport and the production of ATP.
If this process occurs it is likely that the NO would rebind to the same site even in the presence of continuous light. When the light is pulsed however multiple photodissociation events occur, while in continuous wave mode the number of dissociations may be much smaller. This is believed to contribute to the better performance seen from pulsed light.
Maintains Stimulus in ‘Goldilocks’ Zone
Something that we are seeing discussed more frequently in science papers in recent years is the concept that all therapeutic and cellular responses fall into three categories. At the two extremes you have a situation where the stimulus is either too low or too high to induce a therapeutic response. Between these two extremes is the Goldilocks zone where the stimulus is ‘just right’ to induce a response.
It is not only higher peak power which contribute to the enhanced treatment outcomes we see from pulsed light therapy. Unlike continuous wave LED or laser therapy, pulsed light therapy helps to maintain treatments in the Goldilocks zone!!!
To understand why this is the case, requires an understanding of what is happening with free radicals at the cellular level.
Free radicals, or Reactive Oxygen Species [ROS], act as signalling molecules which kick-start biostimulation and are an integral part of how LED therapy works. However, prolonged exposure to moderate or high intensity LED therapy, when used in continuous waveform, can lead to an overabundance of ROS, which can start to slow down and even inhibit cell proliferation and protein synthesis – the very processes which we rely on for increasing collagen synthesis. The reason why ROS slow down biostimulation is because it makes water in the mitochondrial membrane and between cells more viscous, like treacle. In the mitochondrial membrane this has an impact on the last enzyme in the respiratory chain – ATP synthase – which makes ATP. It’s like a tiny motor. And when the water becomes like treacle, the ATP nanomotor can no longer turn as quickly, the production of ATP slows down.
The interrupted nature of pulsed LED helps to mitigate free radical build-up. When the light is on, the mito produce ATP + ROS. When the light is OFF, the cell uses up its ATP reserves and ROS dissipate.
Pulsed PBM ensures that the stimulus never exceeds the Goldilocks zone. This leads to upregulation of ATP and accelerates cell proliferation, leading to increased collagen production and optimising outcomes for skin rejuvenation.
Improved Uptake of Micronutrients / Increased Bioavailability of Active Ingredients
Cells’ that breathe!
Sommer’s research team found that red light at 670 nm, switched on and off alternately, can expand and contract the nanoscopic interfacial water layers naturally present in living cells. When the light is switched on, water from within the cell expands beyond the lipid bilayer that forms the cell barrier. When the light is then switched off, the water retracts back into the cell almost immediately. This process forces the cells to “suck” or “breathe in” molecules that happen to be in their immediate vicinity, which could include anti-cancer compounds. One of the anti-cancer drugs that Sommer’s team are using is ECGC from green tea. Accordingly, Sommer proposed that Maysama should be using pulsed LED to increase the uptake of our skincare active ingredients. This expansion and contraction is thought to happen because 670 nm light interacts with interfacial water; the same effect is not seen in ordinary “bulk” water. “The ‘breathing in and out’ of the water molecules can pull micronutrients into the cell faster and in higher amounts.
In conclusion, if we directly compare LED and laser diode masks, even in pulsed mode, a laser diode mask with the same wavelengths
- Pulsed LED significantly enhances the depth of light penetration and reduces energy loss due to scattering.
- Pulsed LEDs cover a larger area diffusely, which can be beneficial for facial masks, particularly if treating skin surface issues, like skin brightening or acne or is your main concern.
- Laser diodes provide high precision due to their coherent and collimated beam, which allows for targeted application to very specific areas. For deep muscle or joint treatments (where higher energy is necessary), a laser diode mask may still be superior due to its ability to deliver concentrated, coherent energy.
- Pulsing improves mitochondrial activation, potentially making the pulsed LED mask comparable to laser diode masks for treating superficial to mid-dermal conditions, like collagen synthesis and anti-aging.
- Pulsed LED offer a significant price advantage over continuous wave laser diode, making it a very attractive option for Light Therapy Masks for skin rejuvenation relative to laser diode.
When it comes to light penetration, the introduction of pulsed light in an LED mask significantly narrows the gap in performance between LED and laser diode technologies. Pulsed LED reduces light scattering and heat accumulation in tissues, meaning that more energy reaches the targeted depth without being absorbed superficially or lost. This results in improved target tissue stimulation, similar to laser diode technology.
However, comparing pulsed LED to laser diode or the longer wavelengths of 1072nm is a little bit like measuring someone’s leg and trying to guess their weight! The improved biological response from pulsed LED is not simply about depth of light penetration.
A pulsed LED mask could potentially outperform a laser diode mask in overall performance due to the enhanced biological effect of pulsed light. Not only does pulsing increase light penetration but it also impacts therapeutic outcomes by enhancing mitochondria function – the organelles in the cell responsible for producing cellular energy. Due to a combination of higher peak power and the ability to speed up the rate of mitochondria respiration, pulsed LED produces more cellular energy and faster cell regeneration than non-pulsed light. The on/off action of the pulse increases the cellular response and allows cells periods of rest and recovery between pulses. This allows cells to be stimulated multiple times, whilst never exceeding the threshold at which a stimulus becomes less effective due to overstimulation. What’s more, pulsing uniquely allows cells to ‘breathe’ in micronutrients surrounding the cell, increasing the bioavailability of important nutrients needed for cell repair and division, further contributing to its therapeutic advantage.
Pulsed LED is in a league of its own, potentially approaching the performance of lasers for depth of light delivery, whilst providing greater biological efficacy.
There are five parameters that could be specified for pulsed light sources. The pulse width or duration or ON time (PD) and the pulse Interval or OFF time (PI) are measured in seconds. Pulse repetition rate or frequency (F) is measured in Hz. The duty cycle (DC) is a unitless fractional number or %. The peak power and average power are measured in Watts.
Pulse duration, pulse repetition rate, and duty cycle are related by the simple equation:
DC = F × PD
Peak power is a measure of light intensity during the pulse duration, and related to the average power (measured in Watts) by:
Average power = Peak power × F × PD [90 x 100 x 0.2 = 1800?]
Figure 1 graphically shows the relationship between peak power and pulse duration
Source – Hashimi - Effect of Pulsing in Low-Level Light Therapy
Pulse repetition rates (frequency) from 2 to 8000Hz have been found to be beneficial. But the lower end up to 100Hz appears to give an advantage.
The duty cycle and frequency of pulsed light are important parameters, suggesting that certain pulsing protocols better stimulate cellular activity, or promote healing compared to continuous exposure.
Studies supporting penetrative advantage of pulsed photobiomodulation;
Salehpour showed that pulsed LED at 660 and 850nm impacts brain tissue to improve cognitive function. If it can reach brain tissue, pulsed LED can certainly impact deep skin tissue.
Pulsed laser diode has also been used to help treat TBI. Whilst laser is used in this study, the concept of improved biological response from pulsing is relevant.
Miranda demonstrated, when used to treat muscle performance, pulsed PBM (laser + LED) has been shown to provide better physiological effects.
If pulsed LED can impact brain tissue, it can certainly reach deep wrinkles and could potentially exceed the penetration effects of non-pulsed laser diode and 1072nm wavelength. Here are the two studies rerferenced;
Salehpour et al., 2019 –
Research compared the effects of pulsed and continuous transcranial PBM on neurocognitive functions. Results showed that pulsed PBM resulted in greater improvements in cognitive functions and neuroplasticity, potentially due to better mitochondrial stimulation and deeper tissue penetration, which were more pronounced under pulsed conditions compared to CW light. This study uses 660nm and 850nm at 250mw/cm2 and provides direct evidence of the improved penetration and biological response from pulsed light, effective as deep as brain tissue!!
Ando et al., 2011 - The study compared 810-nm wavelength laser irradiation in both pulsed and continuous modes for treating traumatic brain injury in mice. Pulsed laser treatment significantly improved behavioral outcomes and mitochondrial function more than continuous wave treatment, suggesting enhanced neuroprotection and brain recovery with pulsing.
Miranda et al., 2015 - "Phototherapy with combination of super-pulsed laser and light-emitting diodes is beneficial in improvement of muscular performance" - Lasers in Medical Science
This study evaluated muscular performance improvements in patients treated with a combination of super-pulsed laser and LEDs. It found that pulsed phototherapy significantly enhanced muscle strength and endurance compared to continuous treatment. The findings suggest that the higher peak power of pulsed light, albeit for shorter intervals, stimulates better physiological responses in muscle tissue.
Intense pulsed light, near infrared pulsed light, and fractional laser combination therapy for skin rejuvenation in Asian subjects: a prospective multi-center study in China.
This study uses combination therapy of IPL and pulsed NIR and shows that combination therapy gives superior results for skin rejuvenation.
Hashmi et al., 2010. Effect of Pulsing in Low-Level Light Therapy - PMC (nih.gov)
Brondon et al., 2009
Pulsing influences photoradiation outcomes in cell culture - PubMed (nih.gov)
The impact of pulsed LED with melanin filters has been researched by Brondon. Cell proliferation was increased in the group treated with pulsed light, indicating that pulsed light is better able to penetrate melanin rich skin. Specifically, cell proliferation was maximal at 100 Hz (frequencies of 6 to 600Hz were tested).
Brondon undertook a study with red light (670nm) to determine if pulsing light would overcome the filtering effects of melanin using melanin filters. Cell proliferation was increased in the group treated with pulsed light, indicating that pulsed light is better able to penetrate melanin rich skin. Specifically, cell proliferation was maximal at 100 Hz (frequencies of 6 to 600Hz were tested)
- Effect of Pulsing in Low-Level Light Therapy - PMC (nih.gov)
- A 2017 study by Brondon et al., titled "Effects of Pulsing in Low-Level Light Therapy" (published in Photomedicine and Laser Surgery), indicated that pulsed light was more effective at increasing ATP production compared to continuous light for the same wavelengths.
