Over the past couple of weeks, I’ve been getting a lot of questions about how to use RLT and what the right dosages are.

So I decided to make this week’s newsletter about that topic specifically.  

Obviously, this isn’t meant to be a prescription for you, but general recommendations (because I can’t give medical advice over the internet).  What I can do is give you realistic, reasonable, safe guidelines to follow, because more and more people are purchasing these devices.  

As a quick disclaimer, this post contains some affiliate links (Fringe), and I receive commissions through those links. 

With that out of the way, let’s get to the factors you need to consider as a consumer.  

NOTE: I use the terms Red Light Therapy (RLT) and photobiomodulation (PBM) interchangeably throughout the blog.  When I say “red light therapy,” I am also referring to near-infrared (NIR) light wavelengths.  

The Big Picture

What to Look for When Purchasing a RLT Device

There are four primary measurements you want to look out for as a consumer:

  1. Wavelength- in nanometers (nm)
  2. Power- in Watts (W)
  3. Irradiance/Intensity- in mW/cm2
  4. Dosage- Joules/cm2. (or J/cm2)

While these are all key components of what makes a good device, the wavelengths used are by far the most important.  The light must penetrate to where the chromophores exist to achieve the desired outcome.


Wavelength must be correctly depth-matched for the photons to be absorbed in the chromophores inside of us.  In other words, light can only reach the correct tissues when the appropriate wavelengths are used.

Different chromophores in our skin allow for different levels of penetration and absorption.  As you can see pictured above, red and infrared wavelengths can penetrate the deepest, down into the subcutaneous layer and through blood vessels.

Interestingly, water seems to be a chromophore up to 1064nm.  Generally, based on the evidence so far, the best units tend to be in the 600s (red) nm and the 800s nm (NIR) that show therapeutic value.


Power is the rate of energy supplied by the unit.  It is usually expressed in Rated Watts, which is simply the number of LED lights multiplied by the number of Watts given off by each LED.  Here are some examples:

Panels generally range from $250-900 with 12-100+ 3-5W LEDs. The best LED boxes have high quality parts, low flicker LEDs, and varied wavelengths. 


Irradiance is simply the measure of the amount of light energy at the point when it contacts the skin or other tissue, measured as mW/cm2.  Based on most of the evidence covered in the last blog, most clinical studies that report the best efficacy range from 5-50mW/cm2.  It is worth noting that most of the energy given off by the sun falls into this range when it reaches Earth.


Dosage is defined as the energy intensity when a light is applied to an organism, usually measured in J/cm2.  

If you wanted to find a dosage for RLT in Joules, it is going to be based on distance and time.  You are also going to need your irradiance measurement to plug into the formula below:

Target Dose (J/cm2) * 1000 / Irradiance (mW/cm2) / 60 (sec/min) = Time (min)

What Does This Mean as a Consumer?

Replicating sunlight is probably the optimal and safest approach as our skin is finely tuned to its intensity.  Sunlight typically registers around 88 mW/cm2 in intensity.  About 42% of the energy given off by the sun is in the red and infrared spectrum, meaning that direct sunlight emits approximately 37mW/cm2 in the Red to NIR range.

This can be broken down even further.  During daylight hours, the average irradiance of Solar IRA (NIR) is approximately 20 mW/cm2, and peaks around 40 mW/cm2

Exposure to Red-NIR light at intensities mimicking or below solar irradiance (37 mW/cm2) is considered safe and can even be beneficial. However, intensities significantly greater may pose a risk when used incorrectly.

Ideally, if you are in the market for an at-home unit, you want one under 50 mW/cm2.  As one study put it, “Lower irradiance is less likely to induce skin hyperthermia leading to potential deleterious effects.”  

On the flipside, that same study found negative effects associated with units emitting over 100 mW/cm2.  Beyond this range, the authors saw photoaging of the skin.  A stark contrast to skin rejuvenation they saw around 30 mW/cm2

How to Use Your RLT at Home

There are a few major parameters you should consider when using PBM at home:

  1. Distance- skin contact (wrap) or non-contact (panel)
  2. Time – minutes/session
  3. Interval – sessions/day
  4. Frequency – sessions/week

Let’s touch on these in order.


Distance is the most important of the four, and a lot of it goes back to the Inverse Square Law I explained in this blog.

In this context, you’re going to lose a lot more light from panels than you would using a wrap just based on the distance alone.  That is why panels should give off more light than wraps.

In the case of non-contact forms of PBM, the further you are away from a panel, the less therapeutic light you will receive.  Depending on the panel, 60-80% of the energy is lost to the surroundings.  You will also have less penetration the further away you stand (or sit) from the panel.

It becomes a bit of a math game when you account for distance.  For example, a 200W panel can be just as effective as a 1000W panel if you adjust the time and distance:

The positive of using a non-contact source, however, is that you can treat a larger area, and encourage more systemic effects.  There is also less cleanup, since the panel does not touch the skin.

Skin contact allows for greater transmission of PBM.  There is less diffusion and reflection, meaning you can focus the energy on a more targeted area.


Treatment sessions should generally last between 10-30 minutes, although times can vary depending on one’s clinical presentations.  That being said, treatments at home should fall within the timeframes, unless ou are working with a provider directly.  Of course, the greater the intensity of the product you are using, the less time you’ll need using it- unless you change the distance.  

Some common at-home protocols include:

The interval and frequency can change based on many factors.  Some easy ways to gain clarity is by simply knowing what products you are using.  Generally, you want to treat one area of the body once per day.  

If you have a panel, this is pretty straightforward, depending on the size. However, there’s a lot more flexibility when using wraps.  

For example, you can have a session on your knee, and then another session on your elbow in the same day, since there won’t be any overlap.  With wraps, you have the ability to do multiple therapy sessions on different body parts with more flexibility than you would with a panel (depending on the size).

It is important to know that the benefits of PBM are cumulative when applied repetitively, to a point.  In other words, it is possible to overdo it.  Generally, overdoing it isn’t as harmful as the effects of visible light or UV (if you’re not adapted to it), it seems to just lose its beneficial effects.

As this study puts it,

“The dose from one treatment lasts some time and what “remains” of the dose is added to the dose at the next treatment. Adequate time between doses is essential to allow the cells time to respond to the initial dose and will also avoid a situation where the accumulated dose eventually ends up above the bio-stimulating range or even in the bioinhibitory range, with consequently poorer results.”

The best data right now suggests that the benefits of one RLT treatment can last up to  24-48 hours following a single session.

What is a Reasonable Protocol?

So what is a reasonable interval and frequency for RLT at home?  One session per day per body part, 3-5x/week.  This chart breaks everything we just covered down into something easy to use at home (courtesy of Fringe):

What to Watch Out For

Although rare, there are some documented contraindications for RLT, including:

What You Should Feel

You may experience a mild warming sensation when applying RLT.  This is totally normal!  You shouldn’t be concerned or worried if this is the case. 

What isn’t normal is feeling hot.  If the product is making you feel hot, then consider discontinuing use, increasing the distance between the device and skin, reducing the intensity of the light, or reducing the time in front of the light.

If the intensity is too high, you may experience side effects like:

Factors that can impact the warming sensation include skin tone, hormone cycle, light sensitivities (often from medication use).

Skin Tone

Darker skin contains a higher amount of melanin than lighter skin.  Melanin can absorb all wavelengths of light.  This means that the darker the skin tone, the more melanin, and the more light that will be absorbed from any light source, including an RLT device.

So based on the Fitzpatrick Scale, Type I skin types can tolerate a greater dosage than Type V or Type VI.  This isn’t necessarily a good or bad thing.  It is just worth knowing so you can adjust the length of your sessions or increase the distance between you and your device accordingly.


Photosensitivity, or sensitivity to light, is becoming a bigger issue as more people are using medications that play a role in it, on top of living lives that are mostly indoors.  Some common medications that can increase photosensitivity are:

If you can tolerate 20 minutes in the sun, you’re on the right track.  If you can’t, then it’s time to build that solar callous and refer to the beginner sunlight protocol at the end of this blog (and of course, work with your prescribing doctor to reduce the medication usage when appropriate).

If you encounter any of the following signs while using RLT:

…You may want to consider using eye protection during your sessions when starting out. 

In the beginning, the lights may seem overwhelming.  You may find yourself squinting, have an urge to look away, or simply close them.  It is possible to see “spots” during and after treatment.  It is also possible that your color vision and perception is temporarily altered (usually everything looks “greenish”). 

If you experience any of these initially, know that they should diminish quickly after treatment and with regular use of RLT.  If they don’t or are too uncomfortable – use eye protection.

These symptoms commonly disappear with more frequent usage.  This is all part of the eyes adapting to their new surroundings.  

RLT is Therapeutic for the Eyes!

RLT can offer significant therapeutic benefits for the eyes. It operates within the visual system at a cellular level, effectively reducing inflammation in eye cells, and can improve visual acuity.

PBM treatments enhance ATP production within the eyes, thereby improving visual function. Furthermore, they have the potential to enhance tear gland function and optimize tear chemistry.  Additionally, PBM stimulates the upregulation of cytoprotective factors, providing protection against cellular damage.

Moreover, light penetrates the cornea and lens, impacting rods and cones, which subsequently influences proteins responsible for hormone modulation and the regulation of circadian rhythm.


RLT is contraindicated over the abdomen during pregnancy.  It’s worth noting that this recommendation is based on a lack of research, NOT on proof that it is actually unsafe.  The truth is, you don’t see many studies done on pregnant women for most interventions (pharmaceuticals, herbs, or other interventions) because no one wants to risk the one adverse event, understandably so.  It also would be tough to find people who would agree to sign up.  

But that doesn’t mean you need to avoid it altogether.  Red light therapy is generally regarded as safe for the majority of pregnant women. However, I recommend consulting with your healthcare provider before starting your own at-home RLT regimen.  One study involving 67 pregnant women with depression, the use of bright or dim RLT for 30 minutes upon waking up over a span of 6 weeks resulted in a noteworthy 50% reduction in depression scores.

EMFs & Flicker

These are electronic light devices, so nnEMF emission and flicker rates are important to consider when purchasing a product.  As covered in previous blogs, nnEMFs can exert many detrimental effects on the body, including:

You can mitigate nnEMF exposure by opting for products with no- or low-EMF emissions, like Fringe.

Modern fluorescent and LED lights flicker (rapidly turn on and off) many times per second, due to it being an alternating current.  To some degree, flicker occurs in all light sources with an AC power supply delivered at a frequency of 50-60 hertz, meaning the electrical current travels backward and forward 50-60 times per second.

Flicker disrupts the balance in the nervous system.    This can lead to common symptoms like:

Minimal flicker, less than 1%, is considered safe. However, higher levels of flicker can pose risks, potentially leading to issues such as headaches and even seizures.


Pulsing refers to the rapid cycling between “on” and “off” states of an LED or laser device. Typically, pulsing is administered in a 50:50 ratio, meaning that the duration of light pulses “on” and “off” for equal amounts of time.   Since the light is only on for half of the time, the user will only receive half the dosage compared to when it is continuously on.  Pulsing is often used to prevent significant tissue heating and to minimize skin damage, particularly with high-intensity LED red light therapy devices or lasers.

The “quench period” (pulse OFF times) serves to reduce tissue heating, enabling the use of potentially higher peak power densities than those safely achievable with continuous wave (CW) therapy. As far as we know, short-pulse infrared laser therapy is therapeutic, but it doesn’t offer any additional health benefits.

Avoid using pulsed devices if you suffer from seizures or have light sensitivities.

Wrapping Up

Final Guidelines

For at home use:

  1. Wavelength: 600s nm & 800s nm
  2. Intensity: 5-50mW/cm2
  3. Distance: for Fringe Panels- 4-6in.  (Varies depending on the the output of the panel)
  4. Time: 10-30 minutes per session
  5. Interval: 1 session per day per body part
  6. Frequency: 3-5x/week

So I hope this newsletter has given you some clarity on how to use your RLT device.  If you’re in the market for one, I hope this helped give you some clarity on what to look for in a product.

I must also mention my favorite red light and infrared light devices are from Fringe.  Here’s why:

From now until May 22nd, my code VIN15 will be available to save 15% off ALL of their products, and you can check them out using this link.

How is light shaping your life?

Dr. Vincent Esposito

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