Red Light Therapy: The Ultimate Guide -- Bestqool
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Red Light Therapy: The Ultimate Guide -- Bestqool
Create on 2022-11-15
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Red light therapy has gained a lot of attention today, and there is already a myriad of research and clinical studies to explore the effect of red light therapy under different medical conditions. And study results varied among all these research. To clarify this complexity, you should have already piled-up a list of queries. Are there actual benefits of red light therapy for your conditions? How to apply red light therapy for your successful treatment? How long does it take to see improvements? And even more wonderings you may have. If you want to learn how red light therapy works, the benefits of different medical conditions, how to use it to achieve optimal results, and how to purchase an ideal device for your budget, you will love this guide.

Red and near-infrared Light Therapy - What It Is

Red and near-infrared light therapy is one type of light therapy (light-based modality) to trigger the photochemical process in vitro known as photobiomodulation (PBM). PBM is a nonthermal process involving endogenous chromophores eliciting photophysical and photochemical events at various biological scales. A non-thermal process means it is not caused by heat but by light.

A diode-based light source is the most available option in this field due to its ability to emit a particular wavelength or a very narrow band of wavelengths. Light-emitting diodes can transfer energy from heat into the form of photons, depending on the materials. Compared with other light sources, this technology can produce photons at the targeted narrow span of wavelengths.

Red and near-infrared light therapy targets wavelengths around 660 nm and 830 nm, which are the most-studied wavelengths and have shown to be the most general use in the spectrum. There have come to be two forms of light: low-level laser therapy and LED light therapy. Both sources of light share the same mechanism of action and are both commonly generated using diode technology. When employed and investigated in therapeutic applications, both lasers and LEDs are often built to emit similar wavelengths, either in the red or near-infrared spectrum and have been shown to share similar medical functions related to pain and inflammation reduction. Significant differences between the two do exist, however, including the power generated, the wavelength specificity, and the physical characteristics of the Both lasers and LEDs can produce monochromatic wavelengths and have been demonstrated to have pain and inflammation reduction capabilities when employed and investigated in therapeutic applications. However, there are significant variations between the two, including the power generated, the wavelength specificity, and the physical features of the diode-generated beam. The term "low-level" remains a bit ambiguous due to different dosages, but generally, it refers to low power in laser therapy (usually less than 5 mW) to eliminate the damage from heat, while LEDs consume even less power to operate, and are more flexible in production in terms of different optical features.

The photonic energy can help to reach deeper tissues, participate in photobiomodulation procedures, or assist with the activity of other stimuli. The photon absorbers in the endogenous environment will cause the chain of photodynamic modulation, and there are significant photon absorbers in the mitochondria, cytochrome c oxidase, which absorbs red and near-infrared radiation, leading to a chain that enhances the respiratory output, ATP production, and other beneficial syntheses.

About PDM what you should know -- The mechanism behind red light therapy

There are several main mechanisms at the cellular level behind red light therapy. This section is only for geeks, and if you don't feel interested in what actually happens behind PDM, you can jump it over.

The primary photoreceptor is the bound water, i.e. nanoscopic interfacial water layers (IWL), in one recent study in 2019, which overthrew the previous beliefs in the mainstream. When we use R-NIR lasers in LLLT to irradiate cells or tissues, the photons interact with both biomolecules and the intracellular and intramitochondrial IWL masking surfaces. The report reviewed the previous comparable experiments on the effect of red and near-infrared light therapy on accelerated proliferation, ATP upregulation, and uptake of photosensitizers in the pulsed mode. The report shows noteworthy evidence that a higher pulse frequency or continuous mode of light doesn't produce a better therapeutic result than a lower frequency of light, which implies another interactive factor with red and near-infrared light, i.e., the bound water.

laser red light

The three physical parameters of IWL are density (volume expansion), viscosity, and interfacial tension, with the first two of which the biologically important impacts are relatively clear as a result of interaction with red and near-infrared light. The observations are explained by the inertia of the aqueous fraction of the cytosol, for the reason that the inertia of the aqueous ensemble in the densely crowded intracellular space opposes a similar effect when the cytosol instantly expands its volume in response to low pulse frequencies of light, which causes a change in density, according to the author.

Based on one experiment in the study on forcing the cells to uptake the drug dissolved in the culture medium, it identified the physical mechanism of the uptake as transmembrane convection (light-cell-pump), and explained it a posteriori on the basis of the expansion in IWL volume in response to irradiation; furthermore, the conviction is transferred to explain the maintenance of a metabolic effect, comprising the uptake of molecules, including nutrients, adjacent to the plasma membrane.

As for the second parameter, which is induced by bio-stimulatory intensities of R-NIR laser light, the reduction in IWL viscosity, the keys are ROS and the speed of rotation of the mitochondrial rotary motor (ATP synthase). Whenever cells are deprived of their native environment (in vitro) or in the vicinity of injured tissues (in vivo), they experience stress. This manifests itself in the form of extended bursts of mitochondrial ROS, leading to an increase in viscosity. Due to the predominantly hydrophilic intramitochondrial space, an unavoidable physical consequence of the associated increase in IWL viscosity is the decrease in the speed of rotation of the mitochondrial rotary motor (ATP synthase), which must react sensitively to changes in viscosity as a result of its small inertia and very high speed of rotation (under normal conditions, the nanomotor operates at ca. 9,000 rpm), as referenced in the report.

To fully explain how the frequency of light has an impact on the stressed cells, the author elaborated on this point based on the synergistic effect of enhanced metabolism (light-cell pump) and a reduction in IWL viscosity. High pulse frequency can force the expansion in IWL volume in response to irradiation and therefore drive the light-cell pump-a precondition for cellular molecular uptake via the convective route. However, when the pulse frequency exceeds a certain value at which the intracellular IWLs expand in synchrony with the pulsation, inertia prevents the water molecules from driving the light-cell pump, and the increase of ROS contributes to the rise of IWL viscosity, which will cause the deficiency of ATP synthase. This pathway also explains why the pulse mode of light is more effective than CM, as declaimed in the report.

how atp reaction

The study Proceedings of Light-Activated Tissue Regeneration and Therapy Confere by Darrell B. Tata and Ronald W. Waynant pointed out the pathway of cellular culture. The important factor is that hydrogen peroxide is stimulated to generate and pinpointed by light to seek out disease cells that need it. The medical use of hydrogen peroxide is well known through numerous studies, and there are as many similar diseases and ailments for which it has been found effective as there are for light therapy, which implies that the light-inducing generation of hydrogen peroxide does exist and provides some benefits. The author wrapped up that the hydrogen peroxide mechanism does explain, to a large extent, the curative effects of light therapy. At the same time, temporary intense irradiation will also stimulate the increase of Reactive Oxygen Species (ROS), on which the study Effect of red light and near infrared laser on the generation of reactive oxygen species in primary dermal fibroblasts thoroughly discussed. Though oxidative stress essentially brings damages to cells, it also brings potential benefits as it stimulates the antioxidant mechanism. Low levels of ROS could affect gene expression and activate cellular gene expression profile towards increased production of antioxidants, which will strengthen healing mechanism, reduce inflammatory symptom and enhance immune system in a long run, to bring systematical benefit to your health level.

use red light near infrared light to charge cells

The last well-studied photoreceptor in mitochondria is the cytochrome c oxidase, leading to ATP production and a series of pathways related to cell adherence and proliferation, though, in some articles, it is a bit of controversy. Nevertheless, the cytochrome c oxidase is still an important photoreceptor of red and near-infrared light, the remaining confusions are due to the complexity of the subsequential pathways around it and the lack of concrete ascertainable data. But it is doubtless that cytochrome c oxidase plays an important role in metabolic regulation.

The main function of cytochrome c oxidase in our body is to help ATP synthase from two aspects. Mitochondria harbor a series of multi-subunit complexes that perform electron transfer and proton translocation from the internal mitochondrial matrix space to the inter-membrane space (IMS) through the inner mitochondrial (IMM). Cytochrome c is found on the IMM's IMS face and uses a haem prosthetic group to transport electrons from complex III to complex V, i.e., cytochrome c oxidase. As the last enzyme in the respiratory electron transport chain of cells across the membrane, it receives an electron from each of four cytochrome c molecules and converts it to one oxygen molecule and four protons, to produce two molecules of water, which is called inner aqueous phase in cell respiration; besides, it transports another four protons across the IMM, to create the transmembrane difference of proton electrochemical gradient, which is later to be utilized in ATP synthesis. The study Functions of Cytochrome c oxidase Assembly factors details its mechanism and assemblies.

mitochondrial electron transport chain

There are abundant studies that shine a light on the potential signaling pathways.

The study Gene Expression under the Laser and Light-emitting Diodes Radiation for Modulation of Cell Adhesion: Possible Applications for Biotechnology demonstrates that cell adhesion and proliferation can be increased by irradiation with red and near-infrared light of certain wavelengths and decreased when the cytochrome c oxidase is inhibited.

The study, A Novel Mitochondrial Signaling Pathway Activated by Visit-To-Near-Infrared Radiation shows that Cu(A) and Cu(B) chromophores of cytochrome c oxidase could be involved as photoreceptors and various signaling pathways (reaction channels) between cytochrome c oxidase and cell attachment regulation are at work.

One study Photobiomodulation Directly Benefits Primary Neurons Functionally Inactivated by Toxins: Role of Cytochrome c OXIDASE shows that by increasing cytochrome c oxidase activity and cellular energetics, LED light therapy will reduce neuronal cell death caused by the cytotoxin KCN.

Another study, Neuroprotective Effects of Near-Infrared Light in an In Vivo Model of Mitochondrial Optic Neuropathy, also demonstrated a link between the activity of cytochrome c oxidase and prelesion illuminance sensitivity threshold and other retina-related behavioral effects.

Other studies look into the gene expression irradiated by red light. A detailed analysis of the gene expression profiles in human fibroblasts revealed an influence of low-intensity red light with a 628-nm wavelength on 111 different genes that are involved in cellular functions, such as cell proliferation; apoptosis; stress response; protein, lipid, and carbohydrate metabolism; mitochondrial energy metabolism; DNA synthesis and repair; antioxidant related functions; and cytoskeleton- and cell-cell interaction-related functions. The study provides insight that different expressions under irradiation can be an explanation for accelerating wound healing by red light treatment.

Different light sources and the effectiveness of LED therapy

What mainly influences the therapeutic effectiveness of red light therapy is the source of light and its mode, as is implied in the previous section. Among all properties and factors, Light sources directly influence the efficacy of treatment and include mainly low-level visible or near-infrared light from lasers (low-level laser therapy, LLLT) and light-emitted diodes (LEDs). Also, incandescent filament and gas discharge lamps are currently available. An LED light source provides comparable flexibility in design to manufacture light parameters.

A typical LED system is based on a semiconductor chip on a reflective surface. When electricity runs through the system, light is produced. The wavelength of light is dependent on the combination of semiconductors, while the wavelength mainly decides the clinical applications. The study Light-Emitting Diodes lists the clinical applications of all currently available wavelengths of LED sources. LED sources are distinct in that they emit a small narrow spectrum of light in an incoherent way, while in the history of LED development, the original model of LED had no therapeutic effect because the band of wavelengths radiated was wide, up to 100 nm, and it lacked the capacity to generate physiologically relevant energy.

Maximization of LED therapy is strictly abided by optimization of treatment parameters, so the definition of physical parameters of the light source is an obligatory step before setting up photodynamic therapy (PDT): (i) dosage; (ii) irradiance, intensity, and fluence rate; (iii) wavelength; (iv) pulsing or continuous mode; and (v) treatment duration. The most common quantity in the majority of articles, as known as irradiance, refers to the dose of energy delivered by the LED system per surface area of skin treated and is expressed in watts per square centimeter (W/cm2). The optimal clinical irradiance is mostly advised to be around 100 mW/cm2, with a range varying in different medical conditions.

Generally speaking, wavelengths are primarily influential to the curative effect, and both penetration depth in human tissue and effective response are associated with it. The secondary but also decisive parameter is irradiance, also noted as light intensity in some literature, which affects the penetration depth to hit the target area and should guarantee skin safety and health.

Choosing a device to provide a high level of irradiance under safeguard is vital since the higher irradiance will bring more efficient treatment. The general guide from Tidy's Physiotherapy (Fifteenth Edition) suggests that LLLT involves treatment with a dose that causes no serious temperature rise in the treated tissues and no macroscopically visible change in tissue structure. It's not redundant to mention that the actual photodynamic modulation will only be activated after the dosage exceeds a certain threshold in treatment duration per trial.

It is noteworthy that the wattage of a light source does not correlate in any way with its power output, thus with its actual power intensity of light. Power consumption is unrelated to power intensity or light irradiance because a device might consume a lot of energy but still have a low output of light energy, which is generally due to a poorer quality of components used in panel construction, so a high wattage doesn't mean the power is drawn to necessarily converted to beneficial wavelengths. A good manufacturer will measure and label the actual light irradiance for you, and yet there are also approaches to measure the actual output by yourself.

The location and area of treatment are yet considered in the same manner. The larger area of treatment may need a larger panel, and stand a distance away from the source to increase the irradiated area, while the irradiance declines with the proportion of increasing distance.

Both LED and laser light are monochromatic, but laser light is coherent and collimated, so it provides a more focused beam, which is ideal for stimulating chromophores in biological tissue that lies deep underneath or only responds to very specific wavelengths. But in clinical application, laser therapy is also applied at low-level light energy, not only because of the photon damage of laser but also better therapeutical effect due to biphasic dose, so the use of low-level laser therapy at the range between 1.5 and 3 J/cm2, and low-level energy provision, less than 100-200 mW. In terms of the reduction of light scattering and light energy, laser as a light source has its advantage, but it cannot be a good option for healing surface-level problems. LEDs usually emit light in a small band of wavelengths (~20 nm wide) but cannot emit a single specified wavelength (~1 nm wide), and this bandwidth impacts their ability to dial in the wavelength to optimally target desired tissues. In comparison with both light sources, LED light therapy can be more versatile in various applications, and it is a better at-home therapy choice, since it requires fewer precautions or complicated medical preparation, with numerous studies proving that LED light sources can provide practical effects as much as the laser source.

Bestqool company offers products with insurance to meet the FDA and ETL standards. With all our red light devices fully FDA registered and ETL certified, Bestqool devices comply with the highest electrical performance and safety standards to guarantee your healthy and effective treatment. Through a variety of models, from portable to at-home devices, from aesthetic use to physiotherapeutic use, Bestqool assists your health conditions in different proposed scenarios and medical conditions.

In a nutshell, to choose a suitable light source for long-term use, it is indispensable to determine the treatment area, the location of the lesion, the output energy of the device, its pulse mode, and the wavelengths provided. In a comprehensive concern, choosing a light source more ease-to-use and convenient to arrange into your daily schedule is wise.

The current LED-based therapeutic approach in different ailments or diseases.

red light therapy benefits
  1. Skin rejuvenation and repair.

Numerous studies show PDM is an atraumatic approach and bypasses the initial destructive step by directly stimulating the skin's regenerative process, which means it is different than skin rejuvenation modalities based on secondary tissue repair induced by causing controlled damage to the layers of skin, like laser resurfacing or intense pulsed light (IPL). PBM has been successfully administered to reduce common symptoms of laser resurfacing and IPL treatments, with what's commonly known in laser surfacing or IPL, like inflammation, pain perception, or prolonged social downtime. Many clinical trials have proven its efficiency to improve pleasant skin feeling, improve skin appearance, increase intradermal collagen increase, and visibly reduce fine lines and wrinkles.

red light therapy for reduce wrinkles

Here is one study of a controlled trial to determine the efficacy of red and near-infrared light therapy in skin rejuvenation. The data is collected at baseline time and after 30 treatment sessions, and the result is evaluated by both blinded clinical photographs and collagen ultrasonography scans. The assessment verifies the significant improvements in both the visible reductions of fine lines and wrinkles and the increment of collagen density after 30 sessions of treatment. The picture below shows collagen increase using ultrasonography technology.

does red light therapy tighten skin

2) Healing acne vulgaris or other chronic inflammatory disease

Acne vulgaris is a chronic inflammatory disorder of the pilosebaceous unit affecting more than 85% of adolescents and often persisting into later adulthood. Because of the anti-inflammatory function of red and near-infrared light, several studies examined its efficacy in acne treatment in comparison to different light sources, including intense pulsed light (IPL), photodynamic therapy (LED or laser light sources), and pulsed dye laser.

More recently, in a large self-controlled multicenter trial with 397 patients in China, low-dose ALA (5-aminolevulinic acid 5% gel) with one-hour incubation and 633 nm LED light resulted in overall clearance rates of 82.1% after three or four treatment sessions.

Similarly, a randomized trial comparing IPL, PDT, and blue-red LED in Chinese subjects, reported that 58% of subjects treated with IPL achieved ≥90% acne clearance at 1 month compared with 92% for PDT and 44% for blue-red LED.

In a split-face trial comparing 500–700 nm light plus ALA versus light alone, it is found improvement of inflammatory facial acne in both ALA-PDT and light alone treated. However, lesions decreased significantly after one treatment on the ALA-PDT site compared with after two treatments on the light monotherapy site, and ALA-PDT was associated with greater mean acne reduction (87.7%) compared with light monotherapy (66.8%) at 12 weeks.

Another study reported the comparable effects between RLT alone and BLT alone for mild-to-moderate acne vulgaris. At the 2-week follow-up, the average improvement rate of total acne lesions was 36.2% in the RL group and 30.7% in the BL group (p > .05). The average improvement rate of inflammatory and non-inflammatory lesions was 51.5% and 17.3% in the RL group, compared with 26.4% and 10.0% in the BL group (all p > .05). Treatment-related adverse reactions were observed distinctly in the BL group.

Apart from the acne vulgaris, with the well-documented anti-inflammatory ability of red light therapy, it is also beneficial to attenuate other syndromes with chronic inflammation, like rosacea.

red and nir light therapy on acne healing 3) Would healing

Fibroblasts are the major cells in charge of the production of collagen, glycoaminoglycans, and proteoglycans, which are primary components of the extracellular matrix. That's the reason why fibroblasts are critical in supporting normal wound healing, during which the key processes, acting as breaking down the fibrin clot, and creating new extracellular matrix (ECM) and collagen structures to uphold the other cells, are associated with effective wound healing. The article, Wound Healing and the Role of Fibroblasts explore and summarises the research evidence on the role of fibroblasts, their origins and activation, and how they navigate the wound bed, as well as how their activity leads to wound contraction. Several studies investigated the effect of red and near-infrared light on fibroblast proliferation.

One study designed an experiment on L929 (mouse fibroblasts) and HGF-1 (human gingival fibroblasts) cells and found that under an exposure time of 5 min at 5.5 and 8.5 mW/cm2, the cell proliferation in the light exposure group increased by 10 to 18% with increasing light intensity compared to that of the control group, the optimal dose of 660 nm light was determined to be 8.5 mW/cm2 for 5 min, which corresponded to an energy density of 2.55 J/cm2. A similar result can be gained from the group of L929 cells with different optimal doses and the same wavelength, 660 nm from the same device. On the other hand, some study chose laser light therapy reported lower energy doses showed increased proliferation while higher energy doses will contribute to cell inhibition. The picture illustrates the fibroblasts proliferation with changes of red LED illumination time and intensity compared to the control group.

changes of red LED illumination time and intensity compared to the control group

A study observed from on mice experiment, with a 670-nm LED red light source, that the healing acceleration in the skin of SKH-1 hairless mice after incisional injuries, but light exposure is not as effective for burn injuries.

One important study certified a conclusion that illuminates the fact that LED and LASER promote similar biological effects, such as a decrease of inflammatory cells, increased fibroblast proliferation, stimulation of angiogenesis, granulation tissue formation, and increased synthesis of collagen. The irradiation parameters are also similar between LED and LASER. The biological effects are dependent on irradiation parameters, mainly wavelength and dose.

One experiment took human dermal fibroblast subpopulations to validate the effectiveness of red and near-infrared light to activate the fibroblast response in the human body and suggested a new avenue to address cutaneous conditions. Specifically, another experiment claimed that red light (630 and 680 nm) yielded higher proliferation of fibroblast cell numbers, in comparison to infrared light (830 nm), which could be effectively used to stimulate the healing process and promote rejuvenation. Interestingly, 680 nm LED was shown to increase the level of collagen type I in dermal fibroblasts which could eventually lead to higher production of collagen. A more comprehensive analysis on this aspect can be referred to in this study, which examined the relevant variables and laid a conclusion that dual-wavelength light (635 nm + 830 nm) performed better in stimulating the effect on proliferation and collagen synthesis of human fibroblasts in vitro. Most speculations varied based on the optimal choice of wavelengths, dosage, and experimental culture, but all evidence found an effective response of fibroblast proliferation in the irradiation to red and near-infrared wavelengths.

4) Brain health, memory restoration, or other neurological applications

The striking characteristics of near-infrared wavelength to penetrate into bone or skull provides a promising non-invasive approach to benefit brain-related diseases. The study of the transcranial red and near-infrared light transmission demonstrates that near-infrared measurably penetrates soft tissue, bone, and brain parenchyma, in comparison to negligible red light transmission in the same conditions. Transcranial brain stimulation with IR radiation is the use of coherent or non-coherent light to rehabilitate neurodegenerative brain diseases or traumatic brain injury and modulate a neurobiological function in a non-thermal effect.

Based on the assumptions that red and near-infrared light will activate ATP production and enhance cellular respiration, one study found that near-infrared light had a function to reverse the detrimental effects on neural cells brought by some toxic substances, like tetrodotoxin (TTX) and KCN. The study aimed at H2O2 (hydrogen peroxide) -induced oxidative stress found the illumination that LED red light markedly activated both catalase and formaldehyde dehydrogenase (FDH), which is crucial to the level of H2O2, in the brains, cultured cells, and purified protein solutions. The accumulated level of H2O2 in the brain, which is also age-associating, may cause a deficiency of acetylcholine, the chief neurotransmitter of the parasympathetic nervous system. The elucidatory pathway can be referred to in the study. This confirms that the reduction of brain H2O2 and FA levels can restore brain Ach contents, and, consequently, LED-based red light therapy not only prevented early-stage memory decline but also rescued late-stage memory deficits in the mice model.

What influences the effectiveness of LED light therapy?

As said before, there are several parameters of light sources and usage considerations that influence the effectiveness of LED light therapy, including (i) dosage; (ii) irradiance, intensity, and fluence rate; (iii) wavelength; (iv) pulsing or continuous mode; and (v) treatment duration. This section will explain in detail how they act intertwined together in photodynamic therapy.

Wavelengths are decisive because of the penetration ability and the optics of treatment tissue. As in another article, we have analyzed the main substances in the skin that absorb light energy and the optical window of the skin. One study graphed the data of the absorbing constituents of the skin, which are mainly water, melanin, and hemoglobin. To talk about the connection between wavelength and curative efficacy, it is necessary to mention three keywords: light penetration, scattering, and absorption. A study, Optical properties of biological tissues, reviews the interlaced relations of these features. As stated, both high scattering and absorption will cause a reduction in light penetration, and the reason is obvious-to get a certain tissue to be treated, the light shouldn't be absorbed before reaching it or diffusing. Skin, fat, blood, or even water will significantly influence the penetration ability, especially the skin, which is the main barrier of high absorption and scattering coefficient. But these coefficients are also wavelength-dependent. At around 800 nm, the absorption is much lower and the scattering coefficient is certainly reduced, all the way up to 1200 nm. The review also developed a physical model to describe photon migration based on optical properties, which can be properly applied in photodynamic therapy.

What influences the effectiveness of LED light therapy

The next important physical features to be concerned with are light intensity and dosage. The design of LEDs can be very flexible, to handle optical variables, and as a result, the actual output of light energy can vary widely. To get an optimized therapeutic result, the light transmission to the treatment location needs to penetrate into the target area and meet the threshold of effective dosage for various diseases. The texture of the treatment location, as mentioned above, can seriously influence light transmission due to the scattering and absorption situations, so it is a factor to consider when choosing light density (in another way, it is also irradiance). It is also conspicuous that light distance will create a more extensive distribution and diffusion of light over the body, but also a less concentrated light beam, and consequently, it will influence light penetration and photon transmission in vivo. Less photon transmission to the targeted area means you need more time to accumulate sufficient doses to trigger the effective therapeutic process.

Dose = Light density* Time range of each session

It is noteworthy to refer to the Biphasic Dosing Theary, which stems from the Arndt-Schulz rule. The rule claimed that the effects of pharmaca or poisons in various concentrations, small doses stimulate, moderate doses inhibit, and large doses kill. Further, there emerges a lot of research to verify and confirm the phenomenon in LLLT, one of which is the study Biphasic Dose Response In Low-Level Light Therapy. But it is also noticeable that dosage must exceed certain threshold for target lesion, to activate the effect process.

how to calculate rlt dose

Technically the measurement of light intensity varied into three terminologies,i.e. light density, irradiance, and fluence rate, and they are different, though with the same unit. According to Wikipedia, radiant density refers to the power density with respect to the directional angle, and irradiance refers to the power density accepted by a surface per unit. While some devices provide anisotropic irradiance, the fluence rate can be better quantity measurement, as it integrates light power which travels through in cubic dimensional area in all directions. To see the more detailed distinctions, you can refer to this article. The significance to quantify the light power to more accuracy, in some studies, it is verified that in fact, the biphasic dose rule of photobiomodulation just establishes that if irradiance is lower than the physiological threshold value for a given target, light therapy does not produce beneficial effects, even when treatment duration is extended. However, the photo-inhibitory deleterious effects may also occur at a higher irradiance, so the light intensity plays an important role in the treatment effect. More evidence found that low-level light therapy is a more effective and ideal choice, as stated in the mechanism section that higher light intensity will actually change the physical parameters of IWL, i.e. density (volume expansion), viscosity, and interfacial tension, leading to a decline of performance.

To dive into this complexity, one review comprehensively analyzed the effect of varying single parameters of the light source on the PDM efficacy and shed a light on the effect of light intensity and power density. In conclusion, most studies suggest the optimal light intensity is around 100 mW/cm2, ranging from 30 mW/cm2 to 160 mW/cm2. Based on the mechanism and physical factors above, the light intensity should be adequate to be able to penetrate into target tissues and dosage should also be adequate to exceed a certain threshold of stimulation. Though most reviewed articles and educational material tend to claim a dose in the range of 0.1J/cm² to 6J/cm² is optimal for cells, with less doing nothing and much more canceling out the benefits, depending on the treatment area and light output of devices, some studies find positive results in much higher ranges, such as 20J/cm², 70J/cm², and even as high as 700J/cm², referring to the section of clinical application. It's possible that a more fundamental systemic effect is seen at the higher doses, depending on how much energy is applied in total to the body.

The complete guide to dosage

The following chart is a general guide to dosage under different medical conditions.


Dose range(J/cm2)



Back Pain


Brain Health








Hair Loss


Joint Pain


Muscle Performance


Oral Candida










Wound Healing


Generally, for health maintenance purposes, we recommend a dosage of not less than 50 Joule/cm2 per session and a frequency of 4 sessions per week, and for treatment purposes, we recommend a dosage of not less than 90 Joule/cm2 per session and a frequency of 5 sessions per week.

What happens before LED red light therapy?

Before an in-office or at-home treatment, you need to have a clean, makeup-free face. At a dermatologist's office, you might receive additional facial treatments before LED light therapy. Wearing safety goggles to protect your eyes from bright lights is necessary. There are several at-home devices -from masks to wands, from targeted treatment to full-body treatment-choose your comfortable position, since instructions vary based on the device you buy, for you need different dosages and time sessions. Be sure to follow the directions carefully and be careful about different instructions for different devices. The portable model of Bestqool red light therapy device (X40 pro) can be applied to a skin-attaching therapeutic process and traveling use. The models X60, Y100, and Y200 vary from half-body size to full-body size, and they are applied to at-home treatment but are not suitable for traveling use. Yet these models can stand vertically and save energy from holding the devices.

The general guidance of Bestqool devices for the treatment session is as follows:

For health maintenance purposes, it is imperative to keep a safe distance from the source with high light density, measure the time for each session to receive at least 50 Joules per trial, and keep a frequency of at least 4 trials per week. For treatment purposes, you should receive at least 90 joules per trial generally.

Based on the general guide, for health maintenance, the models X40, X40 Pro, X60, and X60 pro can generate moderate strength of light density, more than 40 mW/cm2, and it is recommended to stand from 9 inches away and measure the time of each session, not less than 20 minutes to receive at least 50 Joules per trial and keep a frequency of 4 trials per week. If a light source can generate at or more than 100 mW/cm2, like models Y100 and Y200, for health maintenance, it is recommended to stand from 12 inches away, apply for 20 minutes per trial and keep a frequency of 4 trials per week.

For treatment purposes, you should stand 6 inches away from the models X40, X40 Pro, X60, and X60 pro, measure the time of each session, not less than 25 minutes, and keep a frequency of at least 5 trials per week; but if your device is one of the models Y100 and Y200, you should stand 9 inches away from the source, apply not less than 25 minutes per session, and keep a frequency of at least 5 trials per week.

Some people will see benefits within a few sessions of treatments, but generally, it takes a month to see significant improvements. To refer to a more accurate length of time before seeing significant improvements, see clinical data in the section on 'the current LED-based therapeutic approach in different ailments or diseases.

How do I choose the right red light therapy device for me?

Consulting a dermatologist is necessary before you get a correct diagnosis of your skin problems. What looks like aging, blemished skin, for example, may really be skin cancer. Then depending on your treatment area and location, pay the attention to wavelength and irradiance of the chosen device by asking the following questions:

Does it make sure that the delivered wavelengths are most effective in the optical range?

Does it make sure that the irradiance is strong enough to exceed the threshold of effectiveness and penetration requirement for your conditions?

Does it make sure that it is viable to combine it into your regular routine since the device with a lower irradiance power is more time-consuming for each treatment session?

Does it make sure that the device is guaranteed with a long warranty?

Bestqool has done the research for you and provided the best option for your successful treatment. All Bestqool products are guaranteed by a three-year warranty and reach the highest standards and performance of medical devices of FDA and ETL. What makes Bestqool different is that it provides high power of light output and irradiance measurement, based on the high quality of components which can convert power consumption into effective wavelength efficiently, and higher irradiance affiliates your treatment with more convenience and efficient experience. Our devices are at the level of proficiency, 10 minutes of irradiation with our devices is equal to 20 minutes of irradiation with other devices. Bestqool provides professional light therapy devices a range of devices for all sizes and different uses, from the potable model to at-home model, from the band for versatile use to the wand for target treatment, from the aesthetic series to the treatment series, to more features about out products, you can visit our website:

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