How Safe is Red Light Therapy? Contraindications and Side Effects Reviewed
Is Red Light Therapy Safe to Use at home? This is a very common question we get about our products and Red Light Therapy.
So it might be time to explore the safety profile for red light therapy, how safe is it, where there may be contraindications, and how side effects are produced and tips to avoid issues.
In this blog we have compiled one of the most complete list of references for the safety profile for Red Light Therapy or Photobiomodulation. So we highly encourage after reading our summary, to read some of these references yourself.
As always, we are primarily talking about LED Red Light Therapy, which is known to be safer than Lasers.
You must always defer to your specific device or manufacturer’s precautions and instructions. We are reviewing general safety considerations for educational purposes, but specific devices may have additional safety provisions.
When in doubt, please review your current conditions with your doctor, and ask them if red light therapy is safe or appropriate for you.
Is Sunlight Safe?
When people ask me if red light therapy is safe for them or their situation, the first consideration should be:
Can you tolerate being in sunlight for 20 minutes? Does your doctor allow you outside in the sun with your condition?
If your answer is “yes”, you can enjoy moderate amounts of sunlight, then the odds are high that red light therapy is safe for you!
Red and NIR in Sunlight:
As we know, approximately 42% of sunlight is Red and NIR light! Sunlight is approximately 88 mW/cm^2 in intensity, and thus we can estimate direct sunlight emits 37mW/cm^2 in the Red to NIR range.
ASTM Solar Irradiance Reference Spectrum
This means we naturally have evolved alongside Red and Near-Infrared light, and our body has been adapted to not only tolerate Red/NIR light, but draw benefits from it.
The Safest Wavelengths of the entire electromagnetic spectrum?
Photochemical reactions from UV may cause sunburn, but the safety profile is much better for Red and Near-Infrared light.
Red light therapy in the range of 600nm to 1100nm allows us to enjoy many of the health benefits of sunlight, without the risks of “sunburn” from UV damage, for example.
Do not Exceed:
In a fantastic article titled “Infrared and Skin: Friend or Foe” analyzes the potential risks, safety, and benefits of IR-A (Near-Infrared) exposure. We highly recommend that everyone read it.
In it, the authors conclude the red-near infrared exposure at intensities mimicking or below the solar irradiance (37 mW/cm^2) are quite safe and even beneficial. Intensities that far-exceed solar irradiance will start to pose a risk (more on this later).
The Birth of LLLT: Infrared Light and Cancer
Can Lasers cause cancer? Does near-infrared light from lasers cause cancer?
When the first Near-Infrared Laser was invented in the 1960’s, that was the question that Ender Meister tried to answer in his trials. Not only did he prove that the NIR lasers were safe in his rat testing and did not induce cancer – but they also showed improved hair growth!
So, the first study on the safety of NIR lasers, turned out to prove there are benefits for it!
Red and NIR safety and the eyes:
Just like how we shouldn’t stare at the sun, we shouldn’t stare directly at LEDs or Lasers for prolonged periods of time. We think that eye safety is very important and have written several blogs about it.
- Industry guidelines and limitations for NIR LED exposure in the eye.
- Tips for Eye Safety.
- Tested Eyewear for blocking Red and NIR.
- Will Near-Infrared Cause Delayed Onset Cataracts?
And like most things we will discuss in this blog – low to moderate amounts of intensity and dosage have been shown to be safe and beneficial for the eyes. Excessive intensities become a problem.
Documented Contraindications for Red Light Therapy:
We have found two peer-reviewed articles discussing possible contraindications (one for humans, one for veterinary medicine).  Which the contraindications are very similar for both humans and animals. There is also a great list on the Thor Photomedicine blog which also mentions similar contraindications. 
- Direct Eye Exposure 
Malignancy (Cancer) 
- Several follow-up articles mention the safety and benefits of using photobiomodulation to support treatment or side-effects of cancer. 
Pregnancy   
- Specifically, photobiomodulation aimed at the abdomen during pregnancy is commonly considered a contraindication.
- Paradoxically, all of the articles mention how there is not any feasible reason that red or NIR would even cause harm, mutagenic, or teratogenic effects on fetal tissue.
- One article references a study that exposed chicken embryos to high energy densities and found no teratogenic changes.
- The article also says that the limited penetration of Red and NIR would not reach the embryo through the skin, uterus wall, and amniotic fluid layer. 
- It is implied that treating areas other than the abdomen would be fine, and Thor Photomendicine mentions an application for back pain. 
- Use of Red Light Therapy directly over the thyroid in specific thyroid conditions is not advised.
- Although, two of the articles state that sufficiently low intensity exposure is safe. 
- A recent long-term study with at-home LED devices aimed at the neck demonstrated safety for thyroid (in participants with no diagnosed thyroid issues).
- Epilepsy 
Medications, Lotions, Tanning Creams, or local injections, etc. 
- Some medications, injections, and creams may increase photosensitivity, or should wait to be cleared from the system after use. 
- Generally, it is most suitable to have clean, bare skin for treatment.
- Testicle treatment is generally considered safe and NOT a contraindication, unless when using excessivly high doses. 
- Treatment has been shown to stimulate germ cells, and in vitro studies with NIR light has increased spermatogenisis. 
- A popular study on rat testicles exposed them to excessively-high dosage with NIR light and caused damage. Many people have wrongfully interpreted this study that NIR should be blamed and avoided, when it was clearly the high dosage that caused the problem. 
Hemorrhage and Active Bleeding 
- Due to the increased circulation response from Red/NIR, it is not advised to apply red light therapy to active hemorrhage or bleeding wounds since it may only allow for more bleeding.
Dark Skin, Tattoo, and Hair 
- These things will absorb light more rapidly and lead to heating, pain, discomfort, and adverse skin effects.
- Dosage and intensity are adjusted downward to compensate for darker skin types and pain tolerance. 
Thermal and Heat Effects on Skin:
It is well established by the FDA and in the studies to not exceed skin temperatures of 41 C for prolonged periods of time. Doing so may cause tissue and collagen breakdown.
Studies are generally designed with intensities and dosages that do not raise skin temperature too high, and may employ techniques like additional cooling or pulsing to allow the skin to stay safe.
If skin temperature is controlled or cooled, then it allows potentially higher intensity and dosages to be administered with less deleterious effects.
High Intensity and Dose Skin Side-Effects:
- Heat Rash
- Skin Redness
- Heat Blisters
- “Sunburn” type skin redness
- Erythema Side Effects
One remarkable study recently tried to test the limits of intensity and dosage on human skin for adverse reactions. The common side effects were as listed above, and were reached in darker skin subjects at lower dosages compared to lighter skin types.
Remarkably, this study used ONLY 633nm red light, where it is often rumored that Near-Infrared is to blame for these effects.
Regardless of Red or NIR, typically the adverse response is heavily dependent on intensity and dose, not wavelength (within 600nm-1100nm).
Side Effects of Red Light Therapy Summary:
A recent review article about the use of Photobiomodulation for Inflammatory Bowel Disease shares this summary of possible side effects.
"Such effects have included short-term/temporary feelings of nausea, faintness, tiredness, weakness, shakiness, euphoria, stomach distension, or an increase in the pain of fibromyalgia , and a strange taste in the mouth, headache, decreased appetite, excess sweating, unsteadiness, weight gain, and sleep disturbance in people receiving transcranial PBM in major depressive disorder . " 
Skin Side Effects in Studies:
Side-effects are very rarely reported in clinical studies. But we found two studies focused on skin benefits which reported ertheyma, edema, and crusting.  
Which they report the side effects are all mild and dissipate within 24 to 48 hours. So if you do experience some “sunburn”-like skin redness, usually it should dissipate shortly after treatment has ended.
Anecdotal Skin Side-Effects:
We start to see on forums and social media people with sensitive skin are reporting skin redness, here is one recent example from Reddit.
I was able to easily produce pain and skin redness with a high-intensity 660nm LED device on my YouTube video.
If the red light panel industry keeps making higher and higher powered panels, then we predict that these skin issues may become more common.
It may be important to "slow down" the treatment time and decrease the intensity for safety and effectiveness, despite the propaganda from high intensity panel companies.
Health Canada Declaration – Heat from Low Level Light Therapy:
A recent statement from Health Canada is meant to increase testing and safety considerations for light therapy potentially causing tissue heating and damage. They state that a maximum skin temperature above 45 degrees C will be deemed unsafe. 
Drowsiness, Tiredness, or Dizziness:
Since full-body red light therapy has not been well-studied, we have heard anecdotally that some drowsiness or tiredness is a common side effect – especially for first-timers. Since the body is upregulating energy production and circulation – it may be demanding more water, salt, sugar, minerals, or nutrients. Similar to how a massage or sauna use might require additional fluids or electrolyte replenishment – we may need to do the same before or after red light therapy treatment.
Or, it may be a benefit as one study tracked sleep improvements after full-body red light therapy, and some studies indicate extra-pineal melatonin production stimulated by Red/NIR light.
The FDA’s stance on LED Safety:
The FDA has issued guidance for “Low Risk, General Wellness Devices” – which do not require any FDA registration so long as they comply to the guidance document.
We find that most LED Red Light Panels would easily meet the FDA’s “Low Risk” criteria.
Unfortunately, since the FDA doesn’t take much oversight on LED Panels due to their relative safety, some brands are doing a poor job at self-regulation and quality control.
Other Ingredients: Flicker, EMFs, Pulse, and Blue Light
Since many Red Light Panels originated from Grow Light designs – they are often poorly designed or mitigated for flicker and EMF. Adverse reactions from high flicker or from Electromagnetic Hypersensitivity (EHS) are possible in sensitive individuals.
Some red light panel companies are taking the liberty to add Pulse or Blue Light – which inherently have some safety risks attached. For example, Neutrogena issued a recall for their LED masks due to possible blue light damage to the eyes.
Humans have adapted to the Sun’s intensity in ways to make us resilient to Red and NIR light. In fact, it seems we require some absorption of Red and NIR to live healthy and optimally, which is why photobiomodulation is such an important topic in clinical studies.
For eye safety we have blink/aversion response, eyesockets, eyebrows, eyelashes, and eyelids as ways to protect us from the sun. And even our gonads have hair and are positioned to be sheltered from direct sunlight.
If you have sensitive skin or eyes, or are using a high-intensity product, then you may need to take extra precautons when using Red or NIR light therapy.
If we override our nature and stare at the sun, then that is the problem. If we ignore our senses that our skin feels tremendous heat, that is also a problem. Same thing with Red and NIR, being mindful of intensity and applying some common sense safety techniques, and there should be no adverse responses in most individuals.
Several of the documented contraindications such as Eyes, Thyroid, Gonads – the dangerous effects come from direct exposure, and high intensities and dosages. Where there is quite promising research that low intensity light can be beneficial to these areas, when applied correctly.
Other contraindications like Cancer and Pregnancy are clearly precautionary, and should be evaluated on a case-by-case basis while working with a doctor.
The heat effects on the skin causing skin redness, overheating of the tissue, collagen breakdown, blisters, heat rash, Erthema, and “sunburn-like” symptoms – all of these will become more and more common as unregulated panel companies keep competing to produce the “highest intensity’ product.
And, unregulated panel companies need to be diligent in reducing flicker and EMF, and not adding gimmicky features like pulse and blue-light which introduce new safety issues.
And as a final note, we often find people unfairly blaming Near-Infrared for the heat effects, eye dangers, testicle dangers, hyperpigmentation, etc. But in reality, we see many studies that have used Red light to cause similar side-effects and dangers – and conversely NIR can help improve these areas when used appropriately.
So ultimately the safety profile for Red and NIR (600nm-1100nm) light is highly dose-rate dependent, and not necessarily any particular wavelength within this range.
Keeping these precautions in mind, moderate intensities and responsible usage of Red and NIR LEDs can be very safe for most people.References:
Barolet D, Christiaens F, Hamblin MR. Infrared and skin: Friend or foe. J Photochem Photobiol B. 2016;155:78-85. doi:10.1016/j.jphotobiol.2015.12.014
Navratil L, Kymplova J. Contraindications in noninvasive laser therapy: truth and fiction. J Clin Laser Med Surg. 2002 Dec;20(6):341-3. doi: 10.1089/104454702320901134. PMID: 12513921.
Godbold, John & Riegel, Ronald. (2017).
Contraindications, Special Considerations, and Precautions: Photobiomodulation. 10.1002/9781119220190.ch7.
What are the PBM Therapy contra-indications?
THOR Photomedicine Ltd
Jagdeo J, Nguyen JK, Ho D, Wang EB, Austin E, Mamalis A, Kaur R, Kraeva E, Schulman JM, Li CS, Hwang ST, Wun T, Maverakis E, Isseroff RR. Safety of light emitting diode-red light on human skin: Two randomized controlled trials. J Biophotonics. 2020 Mar;13(3):e201960014. doi: 10.1002/jbio.201960014. Epub 2019 Dec 8. PMID: 31483941.
 Health Canada - skin safety
Lee JH, Roh MR, Lee KH. Effects of infrared radiation on skin photo-aging and pigmentation. Yonsei Med J. 2006;47(4):485-490. doi:10.3349/ymj.2006.47.4.485
Evaluation of subject response following treatment for pigmentation or wrinkles using a diode laser
First published: 28 October 2019
Lee YI, Lee E, Nam KH, et al. The Use of a Light-Emitting Diode Device for Neck Rejuvenation and Its Safety on Thyroid Glands. J Clin Med. 2021;10(8):1774. Published 2021 Apr 19. doi:10.3390/jcm10081774
Ahn, J.-C & Kim, Y.-H & Rhee, C.-K. (2013). The effects of low level laser therapy (LLLT) on the testis in elevating serum testosterone level in rats. Biomedical Research (India). 24. 28-32.
Zhao J, Tian Y, Nie J, Xu J, Liu D. Red light and the sleep quality and endurance performance of Chinese female basketball players. J Athl Train. 2012;47(6):673-678. doi:10.4085/1062-6050-47.6.08