The Science of Light Therapy on Melasma and Hyperpigmentation

How do Red and Near-Infrared light wavelengths affect melanin production in the skin? Can they cause hyperpigmentation or exaserbate melasma? What about other photobiomodulation wavelengths like Blue, Green, Yellow? Does heat play a role in causing a pigmentation response?

While Sunlight and UltraViolet (UV) light are known to affect skin pigment through tanning, recent studies have looked into the influence of other wavelengths of light on skin pigmentation response.

The popularity of Red and Near-Infrared LED panels and many other types of light therapies at home has led to questions if it would affect or worsen hyperpigmentation conditions and melasma, with several anecdotal reports seem to confirm this possibility.

More importantly, light therapies could be used to manage hyperpigmentation and melasma when used properly.

So this blog sets out to investigate the possible interactions of how light therapies and heat affect the human skin pigmentation response.

Disclaimer: This blog is for informational and educational purposes only. It does not offer medical advice for the prevention, treatment, cure, or diagnosis of any medical conditions. Always consult your doctor for any medical recommendations.

Summary:

Only a few small studies have reduced skin pigmentation or treated Melasma with true LED light therapy photobiomodulation. There is still much to be learned about what wavelengths and doses that can be used to reduce or avoid hyperpigmentation.

There are several co-factors of people who are at higher risk of pigmentation response from light therapy treatments, for example Females with Fitzpatrick Skin Type III and higher. So it is even more important to be aware of risk factors and use light therapies appropriately.

The most likely risk of exacerbating hyperpigmentation conditions is the heating effect of high intensity LED devices, regardless of wavelength used of Red or Near-Infrared (NIR). Proper Photobiomodulation is non-thermal by definition, which is what makes it so safe and effective with minimal reported side effects.

Too high of a dose of Red/NIR light therapy produces excessive ROS and NO that can trigger pigmentation responses in the skin. Face masks used on the skin could transfer heat to the user, or have "hot spots" where the LEDs are positioned.

Intensities less than 50mW/cm^2 are often recommended to minimize the risk of skin heating which would lead to deleterious responses like increased inflammatory ROS. Intensities >100mW/cm^2 are often specifically recommended to be avoided to reduce the risk of skin hyperthermia (overheating) and side effects. [1]

Near-Infrared (NIR) is often wrongfully accused of causing heating and hyperpigmentation, yet many studies we find show that proper usage of Near-Infrared can be used to treat melasma or reduce pigmentation and has very low thermal impact.

Red light often causes more skin heating by superficial melanin absorption particularly in Fitzpatrick Skin Phototypes III-VI. This would mean that if someone has to choose between turning off Red or NIR in a panel to reduce heating, it would be turning off the Red.

Avoiding triggers from unprotected Sunlight, UV light, and Blue light on the same days as the Red/NIR LED light therapy treatments can also help prevent a hyperpigmentation response.

Blue light should be cautiously used if trying to prevent hyperpigmentation response, as there are many recent studies showing a direct causal effect of blue light on increasing melanin production. Hyperpigmentation is a common side effect even with properly used blue light therapy clinical trials.

Wavelengths like Green (532nm), Yellow (585/590nm), Red (633nm, 660nm), and Near-Infrared (810nm, 830nm, 850nm, 940nm, 1064nm) all could potentially decrease melanin and treat hyperpigmentation conditions. Contrary to popular opinion, Near-Infrared is often a preferred wavelength to prevent or reduce hyperpigmentation response in light therapy treatments.

Like most photobiomodulation; the intensity, exposure time, dosing, usage interval, and other treatment parameters are more important than just the wavelength. The bioindividuality of the patient and their specific condition may also need adjustments to find the ideal treatment parameters.

Ultimately, we find that properly used non-thermal (and low-thermal) Red and NIR LED Light Therapy will have little effect on skin pigment. It is very rarely (perhaps never) reported as an unintended side effect of dermatology photobiomodulation.[2]  It generally offers protective effects from UV and inflammation, as well improves overall cosmetic satisfaction.

The purposes of this blog is to examine this complex issue and appreciate the possible dosing and mechanisms that red light therapy could have on pigmentation.

Perhaps in the future, more studies will show how we can use photobiomodulation to control the skin pigmentation response. 

11/30/2023 Update: New Systemic Review on PBM on Melasma

A recent Nov 28th 2023 systemic review on the effects of PBM on Melasma covers a lot of the exact same science and reaches similar practical conclusions as we did when we originally published this blog in July 2023.

This is a free to read article titled "Photobiomodulation for melasma treatment: Integrative review and state of the art" by Thais Rodrigues Galache et al.

https://onlinelibrary.wiley.com/doi/10.1111/phpp.12935

Their summary in the Abstract reads:

"Specific wavelengths (red: 630 nm; amber: 585 and 590 nm; infrared: 830 and 850 nm) at radiant exposures between 1 and 20 J/cm² exert modulatory effects on tyrosinase activity, gene expression, and protein synthesis of melanocytic pathway components, and thus significantly reduce the melanin content." [77]

Which confirms with these evidence-based wavelengths and reasonable doses could be used to help manage melanin in melasma.

And they also note many studies showing a possible contraindication with Blue Light on melasma:

"On the other hand, blue light mostly seems to increase hyperpigmentation in melasma rather than treat it" [77]

It is nice that our own blog is validated by this new literature review by published researchers that is in alignment with our own research and conclusions.

Paradoxical Nature of Red Light Therapy and Melanin

A recent May 2023 editorial from Dr. Michael Hamblin titled "Photobiomodulation for Skin Pigmentation Disorders: A Dual-Function Treatment" discusses this paradoxical outcome that sometimes red light therapy can increase skin pigmentation or decrease it. [3]

Red Laser 633nm has been used to increase pigment in Vitiligo treatment trials. Conversely LED Photobiomodulation has been used in several small studies to decrease pigment in Melasma. [3]

The fear is that the reverse can be true. We could cause unwanted pigmentation responses with improper dosing with at-home devices.

This dual-nature of red light therapy is what makes it so interesting and challenging. It falls along the lines of what we know about the biphasic dose response, hormetic response, and trying to find a "goldilocks dose" for particular conditions.

Essentially, we are trying to find which wavelengths and doses will inhibit melanin production in the skin. This can be through direct or indirect mechanisms. We also need to know which parameters will stimulate melanin production so we can avoid those as potential triggers of hyperpigmentation.

Treating Melasma with Photobiomodulation Part 1:

Dr. Hamblin's editorial refers to a study by Dr. Daniel Barolet in treating Melasma with a Photobiomodulation protocol published in 2018 titled "Dual Effect of Photobiomodulation on Melasma". [4]

This pilot study was conducted on seven female patients with melasma that were unresponsive to standard treatment. The study prepared the skin with Microdermabrasion before LED treatment.

The LED device was 940nm Near-Infrared with pulsed light at 50% duty cycle with peak intensity of 90mW/cm^2 and average intensity of 45mW/cm^2. The device was used 2.5 cm away from the skin for 5 minutes per treatment for a total dose of 13.5 J/cm^2.

The results showed a statistically significant improvement in the treated side of the face. Treatment was performed once a week for 8 weeks, but Dr. Barolet comments that three treatments per week would have been preferred for potentially better results.

Dr. Barolet mentions the reason for using 940nm Near-Infrared wavelength was due to a previous in vitro study on isolated melanocyte cell cultures found that NIR wavelengths of 830nm, 850nm, and 940nm initiated systemic mechanisms to reduce melanin production.

"As for wavelength, 830nm and 850nm have been shown to downregulate pigmentation equally well in vitro,²³ so future studies using these wavelengths should to be considered." [4]

So Dr. Barolet is recommending future studies to use Near-Infrared wavelengths to downregulate pigmentation response in melasma or hyperpigmentation disorders.

Treating Melasma with Photobiomodulation Part 2:

The second study Hamblin references is a recent December 2022 study. They recruited 10 patients with mild to severe melasma for treatment with LED light therapy. [5]

The device was 585nm (yellow/amber) LED at 20mW/cm^2 continuous wave (not pulsed) and 20 J/cm (16.6 minutes exposure), once a week for 8 weeks. The device appears to be designed for non-contact method but the distance was not specified.

Again with a positive result:

"Collectively, these results tentatively verify the efficacy and safety of 590 nm LED phototherapy to ameliorate the hyperpigmentation and facial erythema in melasma patients." [5]

Treating Melasma with Photobiomodulation Part 3:

One study titled: "The Management of Melasma on Skin Types V and VI Using Light Emitting Diode Treatment" recruited 60 females aged between 25-60 years with Fitzpatrick Types V and VI who had melasma. [78]

The used Red Light 633nm treatment at 105 mW/cm^2 for 20 minutes once a week and NIR Light 830nm treatment at 55mW/cm^2 for 20 minutes once a week.[78]

After 36 treatments over 9 months there was a statistically significant improvement in melasma analysis. [78]

Reducing Pigmentation with Blue and Red Photobiomodulation:

One 2006 study used Blue (415nm) and Red (633nm) LED light therapy to treat acne vulgaris, but observed pigmentation changes during treatment. [6]

This was also a non-contact device used 3-5 cm from the face. Treatments with 40mW/cm^2 of blue light for 20 minutes led to an increase in pigment, and treatments with 80mW/cm^2 of red light for 20 minutes led to a decrease in pigment.

Treatments with blue light were conducted once a week, then the red light was 3-4 days later - for a total of 2 treatments per week for 4 weeks. There was an overall decrease in pigmentation over the course of the study.

All 24 patients had Fitzpatrick Skin PhotoType IV, and 14 of them spontaneously reported an increase in skin brightness as a positive side effect of the treatment. [6]

Reducing Pigmentation with Yellow and NIR Photobiomodulation

Reducing Pigmentation with Red & NIR LED Light Therapy

A well-designed study that was randomized, placebo-controlled, double-blind, and split face used Red (633nm) and NIR (830nm) LED arrays for skincare. [8]

The study had 112 patients (2 males and 110 females) and split them into 4 groups. Red-Only treatment, NIR-Only treatment, Red+NIR treatment, and control group.

Red light treatments were 105mW/cm^2 and NIR treatments were 55mW/cm^2, both were non-contact at 3-5 cm away and treatments were 20 minutes. Treatments were twice a week for 4 weeks. The Red+NIR group got the NIR treatment first and then the Red treatment second each week.

All treatment groups showed a slight decrease in melanin measurements, with only the Red-Only 633nm group having a statistically significant decrease.

The study concludes the Red+NIR treatment had the best wrinkle reduction, the Red-only had the best melanin reduction, and the highest overall cosmetic satisfaction was in both the groups that used NIR.

"Considering that skin rejuvenation aims at both wrinkle reduction and improvement of skin tone, we consider that the combination of 830 and 633 nm LED treatment would offer the best clinical effectiveness by combining the different bioadvantages produced by these two wavelengths of light." [8]

Reducing Pigmentation with LED Mask for Males

 A recent July 2023 study on 7 males using an Omnilux for Men LED Mask looks at several metrics for cosmetic improvements. [9]

The mask uses 633nm, 830nm, 1072nm - presumably with more emphasis on deeper-penetrating Near-Infrared for thicker male skin. The mask was instructed to use 3-5 times per week, 10 minutes per treatment, for a duration of 6 weeks. [9]

The study does not specify the intensity or dose. The Omnilux website says the device uses 66 double-chip LEDs and according to the GoalsToGetGlowing blog the intensity is 35mW/cm^2. Which we calcuate a dose of 21 J/cm^2 for each 10 min treatment.

Benefits included improvements in fine lines, wrinkles, skin texture, UV spots, and brown spots.[9]

Reducing Pigment with LED Mask

One recent July 29th 2023 study used an LED Mask with 630nm, for 12 minutes, intensity of 21.7 mW/cm^2, and a dose of 15.6 J/cm^2. There were 20 participants (15 female and 5 male) that used this treatment twice a week with recommendation to space each dose by 72 hours to avoid a cumulative overdose. [76]

The authors note the low intensity and wavelength was specifically chosen to avoid exaserbating skin pigmentation problems and heating issues, which can happen more frequently with darker skin types. [76]

The study showed an improvement in many skincare metrics, including some skin lightening effect which they attributed to overall improved skin tone consistency. [76]

Reducing Pigment with LED Mask

One study used a Red and NIR LED face mask on a single female patient. Treatments were daily for 20 minutes for 3 weeks. [10]

The device was reported to use 72 LEDs, but they do not report any other parameters like the actual wavelengths used, intensity, joules/cm^2, or even the brand or model of the device.

The study reports a positive effect for skin lightening. Although overall this study is not very helpful for reproducibility since it fails to report many parameters and only had a single patient.

Hyperpigmentation Response: High Intensity/Dose Red Light Therapy

One study with 100 patients investigated the maximum safe doses with 87.5mW/cm^2 Red 633nm wavelength. [11]

In Fitzpatrick type I-III the maximum was 480 J/cm^2 and Fitzpatrick type IV-VI the maximum was 320 J/cm^2. We calculate that would be 91 minutes and 61 minutes of exposure, respectively. [11]

The dose was administered 3 times weekly for 3 weeks. Over 30% of participants in both skin type groups developed hyperpigmentation, which resolved itself within 3 months after all the treatments had ended. [11]

It comes as no surprise that excessively high intensity and/or high doses of Red LED light can certainly cause a transient hyperpigmentation response as a side-effect.

And we can appreciate the paradoxical nature that several of the studies above used 633nm to reduce pigmentation, but this study with excessive dosing caused hyperpigmentation. So it is never the wavelength alone that causes an effect, it is the dosing that makes either beneficial or detrimental.

Background: Ultraviolet Light and Pigmentation

Now lets roll back to cover some background and basics.

The coloration of human and mammalian skin and hair is mostly determined by the concentration of melanin pigment in the forms of eumelanin and phenomelanin.

Melanin is produced by cells called melanocytes which are stored in the basal layer of the epidermis. Melanin is also stored and transported in melanosomes.[12][13]

Interestingly the concentration of melanocytes are the same in all skin types, but the human skin phototype variations comes from having different concentrations of melanin and melanosomes. [13]

Melanin is known as photoprotective by absorbing UV light, but also has antioxidant and free radical scavenging properties. [14]

Increased melanin production is a natural defense mechanism against light exposure and ROS in the skin. In many climates people experience seasonal variation of the pigment during summer versus winter by nature of tanning from sunlight. [15]

Ultraviolet (UV) light is the short wavelength invisible "light" on the sunlight spectrum. It is divided into UVA (320nm-400nm), UVB (280nm-320nm) and UVC (100nm-280nm).

Ultraviolet light exposure is the most commonly accepted wavelengths that induces tanning of the skin by stimulation of melanocytes and keratinocytes. Depending on the wavelength and exposure, there can be immediate tanning during exposure or delayed tanning effects over a few days or weeks afterwards. [16]

Background: Fitzpatric Scale

The most dominant scientific definition for pigmentation levels of the skin are rated on the Fitzpatric Scale of I, II, III, IV, V, and VI (Roman numerals 1 thru 6).

One study describes it as the following:

It is important to remember this scale for this blog as we will see the interaction of light with various skin types will be different. Wavelengths and doses may need to be tailored appropriately for different skin photoypes.

We will use the shortened term for human Skin PhotoType which is SPT I - VI to not have to repeat the term Fitzpatrick Skin Scale numerous times in this blog.

Background: Types of Pigment Disruptions

Pigmentation disorders (sometimes called dischromia) generally arise from irregularities in the skin's natural defense mechanism to produce more melanin in response to light exposure or inflammation in the skin. The melanin response is generally healthy and beneficial, and these conditions are not life-threatening or directly harmful to the individual.

However, many studies will report that pigmentation disorders resulting in cosmetic abnormality will affect the individual's self-esteem and quality of life, often resulting in depressive and anxiety symptoms. [17][4]

In Melasma, the melanin concentration is often asymmetrical, blotchy, and darker than the bulk the the skin. It typically occurs in areas of the skin commonly exposed to sunlight like the face. [4]

Postinflammatory Hyperpigmentation (PIH) is when inflammation or damage to the skin results in hyperpigmented areas. This can be caused by a wide variety of sources like acne, scars, insect bites, skin irritants, burns, cosmetic procedures and of course UV exposure and excessive light exposure.[18]

Erthyma ab inge is a hyperpigmentation resulting from overheating, commonly associated with being too close to heaters, heat pads, heat from laptops on the legs, and occupational infrared exposure.

"Erythema ab igne is a reticular, hyperpigmented rash that is acquired from moderate heat and infrared exposure, with temperature often ranging from 43 to 47°C [2]. " [20]

One PBM review article addressing the risks of Infrared potentially causing hyperpigmentation notes the following:

"The thermal nature of erythema ab igne means that the irradiance of exposure was elevated and that the cumulative dose (fluence) was very high." [1]

So the reasearchers already know the possible connection between high intensities, high dose, and overheating the skin as a likely cause of hyperpigmentation from red light therapy photobiomodulation treatments.

One study confirms on heat:

"According to the literature, it is evident that melasma worsens after exposure to heat conditions." [78]

In a study mentioned earlier, it produced 30% hyperpigmentation for all skin types with Red 633nm LEDs at high intensity and excessive doses.[11] Perhaps a combination of ROS from the high dose and heating.

Several other types of pigmentary responses are associated with photoaging particularly in people that spend a lot of time in the sun. This can be seen as freckles, age spots, brown spots, liver spots, solar lentigines, and mottled hyperpigmentation. [13]

Risk Groups for Melasma and Hyper Pigmentation Effects

Several studies have outlined the co-factors and risk groups for melasma and hyperpigmentation.

• SPT III thru VI  [13] [20]
• Higher prevalence in females than males
• Peak ages of occurrence are between 20 to 50 years old, with a reduction in prevalence starting at 50+ years. [20]
• Personal or Family History of Melasma and Hyperpigmentation (parents or siblings) [21]
• Hypothyroidism and Addison's Disease [22] [23]
• Other hormonal factors like pregnancy and birth control and other hormonal medications. [17]

Males account for 10-20% of reports of melasma. In males they find similar cofactors of SPT III+, age ranges, occupational sun or heat exposure, hormonal influences, hypothyroid, and usage of unspecified cosmetics. [24] [25]

People whom are in one or more of these categories would want to take extra precautions with light therapies. As we will see these same co-factors are likely more responsive to light therapy in nearly all examples we will discuss later in this blog, particularly SPT III and above.

People not meeting any of these criteria would be reassured they would be at a low risk for an unwanted pigmentation response with responsible usage of light therapies.

Increasing Melanin: Visible Light

Recent studies have shown that Visible Light (400nm-700nm) also induces an increase in pigmentation.

One review article summarizes the following:

"Visible light (VL) is nonionizing radiation that penetrates the deep dermis and subcutis. Pigmentation is found only in darker phototypes (III–VI) after high doses of VL exposure, and only shorter wavelengths (420–470 nm, blue and violet) can induce pigmentation through the activation of opsin 3 (OPN3) receptors in melanocytes [31]." [26]

One study compared the effects of UVA versus Visible light on skin types IV-VI. They found the Visible Light would also show an increase in pigment using 200mW/cm^2 and a minimum dose of 40 J/cm^2 to initiate a response. A dose of Visible Light at 8 J/cm^2 made no effect on pigmentation. [27]

The authors note that despite filtering the Infrared wavelengths, the increased pigmentation doses coincided with an erythema (redness) response likely due to the absorbed light being converted into heat.

They also conducted the same treatments to SPT II, which they found minimal pigmentation response for all doses. Which a common pattern will be that SPT I and II are less likely to have hyperpigmentation responses from light therapy treatments. [27]

A subsequent review article noted the following about this visible light study.

"Greater awareness about the importance of photoprotection against these wavelengths, particularly for patients with melasma and PIH is increasingly needed." [28]

While the lamp used for this study was a broad-spectrum filtered Halogen incandescent lamp with a large amount of the spectrum in the Red wavelengths, more work needs to be conducted to isolate the effects of individual wavelengths on hyperpigmentation.

Increasing Melanin: Blue Light

Many recent articles have confirmed the strong influence of Blue light on increasing pigmentation. The Opsin-3 (OPN3) in the melanocyte has a peak absorption in the blue light which triggers more melanin production. [29]

A review article on the benefits of blue light therapy titled "Blue Light in Dermatology" references 5 articles that resulted in a high percentage of patients with hyperpigmentation side effects, particularly when treating psoriasis. [31]

So while we can appreciate the potential benefits of Blue Light, hyperpigmentation is not a surprising side effect. If Blue Light is used selectively to manage acne, that could be one way to reduce hyperpigmentation from acne scars.

Practical Note: The key aspect in many studies seems to be treatment on "consecutive days" for a sustained hyperpigmentation response. This is also true for many cases of erthyma ab inge that the heat exposure is "repeated" to cause the pigmentation response. Those concerned about hyperpigmentation response may want to reduce the frequency of light therapy treatments. As we can see the contrast of the studies that reduced pigment only did treatments once or twice per week.

Decreasing Melanin: High Intensity Laser Light

While melasma and pigmentation treatments is a very large topic, it is worth here mentioning the high-intensity laser treatments for melasma.

Unlike PBM which is non-thermal, high intensity light and laser treatments are Intense Pulsed Light (IPL), Pulsed Dye Laser (PDL), Q-Switched Laser, Fractionated Laser, and other laser treatments.

These treatments are used for a wide range of cosmetic treatments like skin resurfacing, hair removal, and pigmentation reduction.

For melasma and hyperpigmentation, they generally will use high intensity pulses targeted to damage or inhibit the melanocytes, melanosomes, and break apart the melanin granules. [33]

However, many of the review articles for these high-power light treatments also point out the inconsistent and paradoxical results that may even cause more hyperpigmentation as a side effect. Which could be due to the heat, ROS, or general regression of the issue as it doesn't seem to treat the root cause. [33][34][35]

Dermotological lasers were originally studied in SPT I-III. However, different wavelengths and dosing parameters were needed to improve outcomes for SPT IV-VI, and to reduce side effects like hypo- and hyper- pigmentation. [35][36]

"The safest wavelengths for SPT IV–VI are those in the near infrared range: the 800–810-nm diode and the 1064-nm neodymium-doped yttrium aluminium garnet (Nd:YAG) lasers." [37]

Popular laser wavelengths for treating SPT IV-VI are Near-Infrared 810nm and 1064nm, which seems to be the ideal lasers for bypassing melanin absorption and reducing heat in the upper layers of the skin.

"Currently, low-fluence Q-switched lasers are mainly used in the treatment of melasma [182,194]. Low-intensity treatments mainly use the 1064 nm wavelength, which penetrates deeper into the dermis and leaves the epidermis relatively intact." [39]

Interestingly the dose of the 1064nm laser is rather low at only 4-5 J/cm^2. [40] Which might seem like a low dose in Photobiomodulation, but in this case it is delivered as a high intensity pulse and causes a thermal effect.

"QS Nd:YAG [1064nm] is the most widely used laser for the treatment of melasma. The fluence used is less than 5 J/cm², spot size 6 mm, and frequency of 10 Hz. " [40]

High intensity delivered in a short amount of time causes an inhibitory/destructive action in the cells. Which is an important lesson we commonly point out that it is the intensity and exposure time are most important for light therapy dosing, and just looking at J/cm^2 can hide the true "dose" parameters.

Practical Notes: Although seemingly irrelevant to this discussion of non-thermal LED light therapy, there are some interesting recommendations that should be kept in mind as the science matures. 

1. A clear preference for Near-Infrared wavelengths like 810nm and 1064nm for SPT IV-VI because it avoids superficial heating and penetrates deeper than any other wavelengths. This is likely good advice for ideal Photobiomodulation wavelengths for SPT IV-VI as well, since red light is more likely to be superficially absorbed by the melanin as heat (contrary to popular opinion).

2. Cooling the skin during high-intensity treatment can improve comfort and reduce overheating the epidermis, but too much cryo air cooling during and after laser treatment has shown to give a worsened hyperpigmentation response. [41]

3. These laser treatments will often recommend avoiding UV or Sunlight for days (or weeks) before and after treatment. Which again might be prudent for anyone trying to reduce hyperpigmentation and prevent rebound hyperpigmentation during the course of Photobiomodulation treatments too.

4. While we advocate for low intensity non-thermal LED Panel treatments to avoid pigmentation response, we can appreciate the paradox that high intensity pulsed light when used appropriately has been used to reduce pigmentation.

5. An unsurprising side-effect of high-intensity laser treatments has been hyperpigmentation, so again confirmation that heat and destructive treatments could cause a pigmentation response.

Myth: Green 532nm Light Treatment for Hyperpigmentation and Melasma

A common myth and anecdotal reports have told of Green light therapy for usage on hyperpigmentation and melasma.

We find no direct sources that Green LED or Green Photobiomodulation has been used in peer-reviewed published journals for hyperpigmentation.

However, there are many clinical studies of Green Laser 532nm used in the context of high intensity pulsed treatments for hyperpigmentation.

For example, here is one such study that many people selling green lights will reference.

https://pubmed.ncbi.nlm.nih.gov/14568830/ 

As explained in the previous section, high intensity green laser/IPL treatment is a very different context to green LED photobiomodulation and brands should not use completely irrelevant studies and technologies to promote their products.

We visited this article using high intensity Green and NIR lasers for pigmentation, and here is what they actually used when you read the article:

"Patients with Fitzpatrick skin types I through IV were enrolled in this evaluation for the first and third groups involving the 532-nm laser, and those with skin types I through V for the 1064-nm laser group. This skin type restriction was neccessary because the KTP [532nm] laser is well absorbed by melanin and can be problematic in treating darker skin types. The longer-wavelength Nd:YAG [1064nm] laser alone can safely be applied to skin types V and VI." [42]

Telling people to use Green light based on this irrelevant study would be double-bad advice again since longer NIR wavelengths (810nm & 1064nm) are prefered for SPT IV-VI and Green 532nm would cause superficial absorption and heating with more side effects (including possibly causing more hyperpigmentation as a side effect).

Here are two more high-intensity green laser studies being falsely used to sell green PBM for hyperpigmentation.

https://pubmed.ncbi.nlm.nih.gov/12623553/

https://pubmed.ncbi.nlm.nih.gov/26551773/

This is not a "soothing" green light therapy treatment, this is high intensity pulses to inhibit the cells or destroy melanin/melanosomes. One of the studies showed that 660nm (red) laser did better than the 532nm (green) laser to reduce pigmentation, but it doesn't matter because it is irrelevant to LED Photobiomodulation.

Inconclusive: Green LED for Hyperpigmentation and Melasma

Lets try to find some actual PBM studies to see what they say about Green light on the skin.

One review article titled "Role of Photo-Biomodulation Therapy in Facial Rejuvenation and Facial Plastic Surgery" the author speculates the following even though the reference they provide doesn't have any real data to support it.

"530 nm (green): it might have some benefit for pigmented epidermal conditions and superficial skin conditions like stretch marks but its use for these conditions has not been proven yet." [43]

In that same article on the actual section reviewing pigmentation treatments, the author concludes that Near-Infrared LED wavelengths would theoretically give the best benefit to treating hyperpigmentation:

"Therefore, these LED wavelengths, particularly 830nm, might be helpful therapeutic tools for treating patients with hyperpigmentation." [43]

One review article on isolated melanocytes found that Green (530nm) light had increased melanin synthesis and tanning in SPT II and III (higher SPT were not tested). They noted that Green light activated OPN3 similar to blue light.  [44]

A recent review article titled "The Emerging Role of Visible Light in Melanocyte Biology and Skin Pigmentary Disorders: Friend or Foe?" makes very clear that both Blue and Green light can contribute to photoaging and hyperpigmentation. [78]

A very relevant May 2021 review titled "Role of Visible Light on Skin Melanocytes: A Systematic Review" covers the different roles of blue, green, yellow, and red light on the melanocytes. They say the only documented benefits of green light (490nm-570nm) are for cellulite and wound healing, they don't say direcly how it affects pigmentation. They say green light can increase ROS and photoaging, which would seem to be contraindicated for the goal of reducing hyperpigmentation. Only Yellow light (570nm-595nm) had a direct effect on melanin inhibition according to this article. [45]

A June 2019 review article titled "Under the spotlight: mechanisms of photobiomodulation concentrating on blue and green light." would hopefully give us some insight.[46] They summarize the PBM benefits of Green light merely as:

"Published reports have indicated PBM effects for green light ranging from improved cellulite appearance (32) to reduced tissue swelling (33)." [46]

With no mention of Green light PBM for treating hyperpigmentation.

Another review article covering Photobiomodulation of the skin with Blue, Green, Red, and Infrared also makes no mention of clinical studies using Green to treat hyperpigmentation. [47]

At this point we can safely assume there are no direct studies using Green PBM to treat hyperpigmentation, not even from a mechanistic standpoint. Recommending Green LED is reckless as the mechanisms indicate it could increase hyperpigmentation via OPN3, induce ROS and photoaging, and be superficially absorbed as heat.

The famous brand Celluma similarly could not find any actual published studies on using green LED PBM for hyperpigmentation in their blog on the topic.

Increasing Melanin: Radio Frequency Treatments

Another adjacent "energy medicine" is the Radio Frequency (RF) cosmetic treatments. RF wavelengths delivers heat therapy deeper into the skin is commonly used for skin resurfacing and tightening treatments. The common temperature for treatment is 38C - 44C. [48]

However, there are some reported side effects of hyperpigmentation from this therapy. Similar to the high-intensity pulsed laser treatments, it is unsurprising that a heat therapy has the possibility of causing hyperpigmentation side-effects. [48]

Increasing Melanin: Infrared and Heat

Excessive heat from high intensity Infrared exposure is often associated with increased pigmentation.

"Moreover, although intense heat leads to melanogenesis, there is no systematic study on solar heat (infrared radiation [IR]) in melasma, nor are validated methods to assess IR protection available. Thus, workers submitted to intense heat as cooks, bakers, metallurgists, glassmakers, and drivers should be advised of the role of intense heat in the chronicity of melasma." [33]

Another review article mentions the following:

To date, no systematic investigation has examined the role of solar IR radiation in melasma." [26]

It is clear that infrared and/or heat can initiate hyperpigmentation, worsen melasma, or cause erthyma ab igne.

The problem the review articles keep saying is the lack of studies on the actual infrared wavelengths, intensity, or doses that cause a pigmentation response.

Infrared is a wide range of wavelengths including Near-Infrared, Mid-Infrared, and Far-Infrared (780nm to 1,000,000 nm - yes a million nanometers).

We have already seen several examples where Near-Infrared has a very low thermal effect and is used to reduce pigmentation.

Here is one direct quote from an article:

"It has been reported that IR-A can penetrate epidermal and dermal layers and reach subcutaneous tissues without increasing the skin temperature significantly, whereas IR-B and IR-C are absorbed mostly in the epidermal layers and increase skin temperature significantly (Schieke et al., 2003)." [49]

It is clear the "heating" wavelengths are Mid-Infrared (IR-B) and Far-Infrared (IR-C), which are commonly associated with the exposures that produce hyperpigmentation or erthyma ab inge.

Near-Infrared (IR-A) gets wrongfully assumed to be a heating wavelength due to it's shared name with the longer-wavelength Infrareds. But Near-Infrared is most commonly agreed to being the least-heating wavelengths of the entire optical spectrum, despite the common myths circulating online.

No Effect on Melanin: Far-Infrared and Warmth

One 2006 study titled "Effects of Infrared Radiation on Skin Photo-Aging and Pigmentation" used Far-Infrared therapy on 20 females Fitzpatrick Type III-IV with pigmented lesions. [50]

The study used wavelengths 900,000 to 1,000,000 nm with 35 mW/cm^2 intensity for 15-20 minutes daily (5 days a week) and showed no effect on pigmentation on the patients. [50]

The authors also note the skin temperature was increased to a "pleasant" 32℃ -35℃ , which would mean this treatment could be categorized as low-thermal photobiomodulation despite the long wavelength.[50]

There were improvements collagen and wrinkle reduction, there was no significant effect on pigmentation. [50]

Practical Note: This is a very important example where Far-Infrared exposure that doesn't significantly heat the skin is not associated with directly affecting pigmentation. For example Infrared Sauna usage would not cause pigmentation effects as long as the body is not too close to the heaters to overheat the skin.

Sauna and Pigmentation:

With minimal studies confirming and only a few anecdotes, there is only one published article that mentions that sauna usage is accociated with erthyma ab inge hyperpigmentation in athletes.

"erythematous patches often with telangiectasias and hypo- or hyperpigmentation in areas exposed to excess external heat sources.^51,52 In athletes, these sources may commonly be heating pads, hot water bottles, hot showers, hot baths or whirlpools, hot stone massages, sauna and steam rooms, and heated recliners, especially in those treated for muscle or joint aches or pains" [51]

While sauna is meant to increase core body temperature in a controlled way, the skin temperature should not be excessively high which could be due to sitting too close to the stove or heaters.

No Effect on Pigmentation: Near-Infrared and Warmth

An important emerging new light therapy is called Water Filtered IR-A (wIRA) that uses incandescent light sources with a water filter in front of it. This water filter absorbs the "heating" wavelengths and allows to pass the most of the deeper penetrating Near-Infrared wavelengths.

Here is one descripion:

"wIRA irradiation can effectively heat the skin and subcutis up to a depth of approx. 2.5 cm with a low thermal load on the skin surface while delivering an effective energy level to deeper tissue layers (see Chap. 3, Fig. 3.5)." [52]

They report the goal is to induce mild skin hyperthermia with deep penetrating heat at 39℃-42℃. This is often achieved with intensities 110mW/cm^2 and higher. [53]

"Although applying local hyperthermia (44 °C/30 min) has been successfully used for treating common and facial warts, side effects include burning sensations, blister formation, and subsequent hyperpigmentation [10]. No such side effects have been reported using a wIRA radiator (type 501; Hydrosun^®, Müllhein, Germany) [4], most probably because IR-A components, which would typically cause unwanted thermal stress and a stinging and burning sensation in the skin by interactions with water molecules, are reduced by a water filter [11]." [54]

Despite the purposeful heating with near-infrared wavelengths (which the heating isn't caused by the wavelengths used, but from the high intensity), the researchers report there has been no such side effects like hyperpigmentation from wIRA therapy so far.

Practical note: High intensity LED Panel treatments are becoming heat therapy more similar to wIRA rather than non-thermal photobiomodulation. Skin temperatures should be monitored when using an LED Heat Lamp with >50mW/cm^2 particularly with SPT III-VI. We see that Near-Infrared treatments with controlled skin temperature (<42C) does not have a direct impact on pigmentation on normal patients.

Increasing Melanin: Heat/Infrared Plus UV

One article reported an additive effect of heating plus UVB increasing melanin production. [55]

Another article mentions the combination of Infrared and HEVL (high energy visible light, Violet/Blue wavelengths) also increases melanogenesis. [17]

One article pre-conditioned the skin with various wavelengths before UV exposure. The Near-Infrared wavelengths like 850nm, 870nm, and 970nm appeared to protect the skin better than Red wavelengths like 630nm and 660nm. However, looking closely at the picture, it is clear the Near-Infrared provided protection by facilitating more transient melanin production. [1]

Practical Note: As noted several times earlier, it would appear that avoiding the combination of Heat/Infrared plus UV/Blue during the treatment period would help prevent the melanogenic activity of hyperpigmentation response. Although in normal skin this is a highly protective effect.

Preventing Hyperpigmentation: Red Light Plus UV

Often Red and NIR light therapy is considered to be protective of the skin from "sunburn" from sunlight or UV exposure. One study used 660nm to precondition the skin.

"The results of the study showed a reduction in the UVB-induced erythema reaction in a significant number of the pre-treated subjects. Also a SPF-15-like sun protection factor effect and a reduction in post-inflammatory hyperpigmentation were observed." [1]

There is a protective effect when using Red/NIR before or after UV exposure by attenuating the inflammatory effects. Which could decrease hyperpigmentation responses from UV inflammation, although perhaps with a minor transient protective pigmentary increase.

Red vs NIR: Which Is Less Heating?

The common fallacy is that NIR is more of a heating wavelength than Red. However, we have already seen many examples where NIR is preffered as the least heating wavelength on the skin.

One recent June 2023 article used mathematical modelling of skin optics to determine skin temperature profiles with different wavelengths.

"Because of the higher absorption coefficients, higher temperatures (approximately 45°C) were observed at the skin surface at the wavelengths of 632 and 660 nm, as compared to the longer wavelength of 1064 nm, which produced the smallest temperature increase (approximately 3°C)" [57]

The Red wavelengths have higher skin heating than NIR due to higher absorption coefficient into Melanin and Hemoglobin (blood).

The simple way to understand it is that the deeper the penetration, the less heating occurs at the surface of the skin.

The Near Infrared wavelength is dispersing into a larger volume of tissue due to it's deeper penetration. Which means it's potential heat energy is also spread over a wider volume, leading less superficial heating that would lead to a pigmentation response.

Mechanisms: Melatonin

Aside from directly impacting the melanocyte, there are a few interesting mechanisms that are related to Red/NIR light therapy.

Melatonin is famously known as the nighttime hormone excreted by the pituitary gland to induce sleep.

Recently, it has been discovered that 95% of melatonin is produced in the cells aided by Near-Infrared light exposure, and only 5% is produced in the pituitary gland. [61]

This is a profound discovery. Previously it has been known that Red and NIR light therapy can be used to help sleep and circadian rhythms in general. Now we know it also aids the intracellular production of melatonin as well.

Melatonin had been discovered in experiments that caused frogs' skin to modulate melanin. Researchers found that frogs consuming or exposed to exogenous melatonin caused their skin to lighten. [62]

Since that discovery, it has often been hypothesized that melatonin would play a role in human skin and hair pigmentation. [63]

One survey article found that patients with melasma had lower concentrations of melatonin than people without the condition. Which also was associated with an overall increase in oxidative stress. [64]

One excellent review article published February 2023 titled “Melatonin in Dermatologic Allergic Diseases and Other Skin Conditions: Current Trends and Reports” summarizes the effect of melatonin for skin conditions. They discuss one article that successfully used topical melatonin to treat melasma. [65]

This success is often attributed to the powerful antioxidant effect of melatonin, thus reducing inflammation of the skin and providing a competing antioxidant instead of the skin needing to produce excess melanin. Similar to how many other antioxidants are also employed for treating hyperpigmentation and melasma as well.

We would postulate that Near-Infrared would be a powerful contributor towards anti-inflammatory melatonin production in the cells, thereby being an additional mechanism to appreciate how it can help calm melanin production.

Mechanisms: Heat Shock Protein 70 (HSP70)

Heat Shock Proteins have often been made famous recently as a beneficial effect of sauna therapy.

One study found that using Radio Frequency (RF) treatment to bring skin temperature to 43C for 20 minutes successfully treated 10 female (SPT III and IV) patients with melasma. They hypothesized the increase in Heat Shock Proteins was one of the mechanisms for the results. [66]

One study found higher HSP70 concentrations in depigmented regions of Vitiligo patients. Which could confirm a correlation between higher HSP70 and lower pigmentation.[67]

Several Photobiomodulation studies have confirmed increased activity of HSP70, particularly with Near-Infrared lasers. [68][69]

A review article by Dr. de Freitas and Dr. Hamblin on the mechanisms of photobiomodulation states the following:

"HSP70 is part of the normal wound healing process, alongside IL-6 and TGF-β1. Visible (532 nm) and NIR (815 nm) light have been demonstrated to induce HSP70 expression in treated skin cells, and this is important for skin rejuvenation interventions, since there is a consequent effect consisting on the assistance of the correct folding and transport of newly synthesized collagen [93]." [75]

So this is the only mechanistic glimmer of hope that 532nm green light can induce HSP70 as a possible mechansim for controlling pigmentation, but we also see NIR is often favored for this effect as well.

So once again we could speculate the increased HSP70 activity with controlled low-thermal Photobiomodulation could be a mechanism for reducing pigmentation.

Mechanisms: Nitric Oxide

Nitric Oxide (NO) produced by Ultraviolet light exposure had long been known as one of the mechanisms for producing melanogenesis and associated with the risks of melasma and hyperpigmentation disease. [70][71]

Once again, it has been found that SPT IV-VI respond more greatly to NO than lighter skin types.[72]

In Red and NIR Photobiomodulation, one of the main mechanisms has been the release of Nitric Oxide from Cytochrome C Oxidase to remove the limiting factor from the Electron Transport Chain and produce more ATP. [73]

While Nitric Oxide is beneficial in homeostasis, for example to promote healthy circulation, excessive Nitric Oxide production is one of the assumed mechanisms for the biphasic dose response in Photobiomodulation. [74]

As well it is already known that high PBM doses produces ROS as part of the biphasic dose response, which already holds some risk of Post Inflammatory Hyperpigmentation. [74]

In addition to the potential thermal effects, excessive ROS or NO produced from overdosing Red and NIR light therapy could also be a mechanism for increased pigmentation response from treatments.

Conclusions:

The effects of wavelengths light on hyperpigmentation and melasma is only recently being studied and understood.

Based on the current research, successful melasma treatments on humans have used 940nm NIR and 585nm Yellow light LED photobiomodulaiton. Skin lightening or brightening has been observed in 2 large studies using 633nm Red LED light, and to a lesser degree 830nm LED. Blue light is often confirmed to increase pigmentation.

There are many in vitro (tissue experiments, not on whole humans) studies that show various wavelengths of Yellow, Red, or NIR can also be used to treat pigmentation conditions. So far there is no scientific indication that Green LED Photobiomodulation would be used for treating hyperpigmentation, despite the constant claims otherwise. 

Like all of photobiomodulation, the dosing is just as important as picking the correct wavelength. Improper dosing of any wavelength could lead to an unwanted pigmentation response.

When using high-intensity (>50mW/cm^2) LED panels that cause a heating effect, the skin temperature should be closely monitored to not reach excessive levels. It is possible that minor skin warming by a few degrees C with deeper penetration wavelengths could stimulate several processes to reduce pigmentation.

However, using any kind of heating in conjunction with the NO and ROS from Red/NIR could be a trigger for some forms of melasma or hyperpigmentation. So it may be prudent to always start with low intensities to see how the skin responds.

Contrary to popular opinion, Near-Infrared wavelengths are often regarded as the least heating wavelengths by nature of having less superficial absorption. This is particularly more important for SPT III-VI where melanin absorption of Red light would lead to more rapid superficial heating especially in the epidermis where the melanocytes reside.

We have a wide range of studies that help us use Red/NIR light therapy responsibly and minimize unwanted pigmentation side effects. In the future we expect to see many more studies that will help us control pigmentation effects to our desired outcomes more consistently.

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