Many of the big commercial fads today are related to the beauty industry. The beauty industry goes beyond cosmetics. It brings together all economic niches that offer consumers goods and services to look better. That goes from fashion to fitness, from food to cosmetic surgery, and much more.

In an aging world, or in a world where actual consumers are proportionately older, nothing is commercially hotter than the “anti-aging industry”.

An inconspicuous device that was used mostly for minor joint injuries a couple of decades ago made it there: the red light. We had one of those at home: my mother left me for a couple of minutes under it when I was sore after a fight. I was a competitive fencer and always managed to get hurt.

If you google “red light therapy” today, though, you will get around 8.5 million results. Although pain is still an application, up there on the first page you will see “rejuvenation”. Red “light+anti-aging” render around 4.6 million results on google.

As with most things that grow too fast into fads, the red light became a panacea: claimed benefits include faster wound healing, immune boosting, treatment for hair loss, depression, skin disorders, arthritis and even cancer. A noninvasive, relatively cheap and easy to use treatment for some of the conditions that cause the greatest suffering modern humans face. As Hahm and colaborators (22) suggest, it was the non-invasiveness and patient acceptance of red light treatment that keeps its use, in spite of not being FDA approved or covered by insurance companies. What can be more tempting to try?

That’s where we come in. Massive marketing and insufficient scientific evidence are a bad combination. Let us examine what current research can positively confirm concerning the benefits of red light therapy and whether it is safe [i].

What Is Red Light Therapy?

The preferred technical term for red light therapy is Low Level Laser Therapy (LLLT), but other terms like low-power laser therapy (LPLT), soft laser therapy, low-intensity laser therapy, low-energy laser therapy, cold laser therapy, bio-stimulation laser therapy, photobiomodulation, photo-biotherapy, therapeutic laser, and monochromatic infrared light energy (MIRE) therapy are used interchangeably (14, 22).

The procedure consists of exposing an area of the body to low levels of red and near infrared light. The term “low” specifies that the light densities are low compared to medical laser applications such as surgical cutting or thermal coagulation.

Those who claim LLLT is responsible for a wide range of beneficial clinical responses believe that its effect goes beyond local heat application.

I examined a few user forums and, apart from joint pains, musculoskeletal issues and arthritis, there is not much consensus about treatment benefits (Energeticforum and Realself). The amount of confusion concerning the subject, now, is alarming.

There are people reporting ultra-violet light applications in the red light forums, when violet and ultra-violet light are in the opposite side of the visible light spectrum and have very different interaction with biomolecules.

There are several devices available in the market, from cheap to expensive. Most can be used at home, but there are a few sophisticated systems that are used in specialized alternative medicine clinics.

At the scientific level, there is not much we can positively say. As I will elaborate in the following items, most research measures a phenomenon, or uses by-proxy methods to address possible causes, just to conclude that “the mechanism is unknown”.

Red light application seems to be beneficial to certain injuries and pathological conditions but the panacea claims currently made are not yet backed by research.

How much research is there on Red Light Therapy?

When we think about research on a certain subject and what exactly does “more” research mean, we must consider a few aspects of the nature of scientific production. First, that an increase in published evidence always results from a combination of the scientific community’s interest, public interest as reflected, for example, in public policies or public opinion expression, and availability of research funds and infra-structure.

Research on HIV, for example, was instantly increased once it was perceived as a major public health threat. Most other issues on medical research, which is mostly applied, follow the interplay of what we call market pull and technology (and science) push. Like the proverbial egg and chicken dilemma, sometimes it is hard to discern between what factor was determinant: the need for a certain medical innovation or the interest of the scientific and technology research community in pursuing that route.

Finally, any quantitative analysis of scientific publication must take into account the universal trends in scientific publication (how much of what you are looking at is just a reflex of an overall growth in science).

If we look at the publication trends on red light therapy, there is a steep rise in publication around the year 2000 and soon after that (figs 1-3). If we compare that with patent data on red light therapy devices (fig 4), we observe that they peak more or less around the period when publications start to increase.

Fig 1: Number of published articles per year retrieved from a Pubmed search with the search terms “low+level+light+therapy” (2017).

Fig 2: Number of published articles per year retrieved from a Pubmed search with the search terms “red+light+therapy” (2017).

Fig 3: Number of published articles per year retrieved from a Pubmed search with the search terms “photobiomodulation” (2017).

Fig 4: Number of filed patent documents at the USPTO concerning devices on “red light therapy”. Retrieved from “Google patents” (2017).

Is this a case for market pull? Maybe. Even if it is, the chief question concerns the quality of research, as reflected by methodology and procedures. Much medical research about certain drugs, directly funded by the pharmaceutical industry, was later severely questioned by the community.

That prompted many journals and research institutions to make it mandatory for authors to identify their funding sources. It would be naïve to overlook the potential for bias in procedure and result analysis.

Another concern is the citing procedures. Publications in solid and densely researched subjects have strictly pertinent citing of corroborating evidence.

Examining the peer reviewed original research publications and reviews on LLLT, this is not what I found. Some of the red flags are:

  1. The frequent use of (discreetly placed) disclaimers, such as “the exact mechanism is unknown”, “remains controversial” or “the precise manner is not yet known”, after a paragraph of enthusiastic description of a phenomenon (in all reviews and in primary sources, such as 24).
  2. Miscitations or misquotations

Example: the citation of Dolmans et al (16) work for the claim that LLLT has anti-cancer effects. The cited paper refers to photodynamic therapy, which is a treatment that employs a photosensitizing agent (a drug) and a specific source of light. The light serves as an activating agent to promote active oxygen species production.

  1. Unnecessary, off context or exaggerated descriptions of related fields

Example: long descriptions about the quantum physics aspects of light, “Eastern medicine” concepts of meridians (41) or chakras (31).

Most research is concerned with documenting claims as to the effectiveness of LLLT for the more controversial conditions, such as cancer treatment, wound healing and immune system boosting. I examined two of the recent scientific reviews on the subject that were relatively well published: Chung and collaborators’ article on Annals of biomedical engineering (14), and Hahm and collaborators’ article on Photonics & Lasers in Medicine (22).

The first, which had abundant citations, had too many cases of misquotations and out of context content. The second review “focuses on the ability of LLLT to modulate the peripheral – local and regional – mediators of pain inciting agents” (22). Again, about 30% of the text is a description of the physiology of pain and inflammation. The rest offers putative mechanisms for the observed in vitro and in vivo results. In the end, all we know is that there are positive results of LLLT application on inflammatory conditions.

Official health care government acceptance or, worse, insurance company acceptance of some treatment’s scientific basis is not exactly the best criterion for scientific soundness. However, the fact that none of them found sufficient basis to approve this treatment (2, 3, 1) and that even the Cochrane foundation meta-analysis (43) found inconclusive data to its claims is something to consider.

What has the research concluded?

The objective of medical research about a given treatment that has empirically or even anecdotally shown benefit is to understand how and why it produces the observed results. Of all the research I examined, the studies that offer less controversial results are based on observations made on humans.

Those refer to LLLT effect on joint pain, such as tendinopathy (38), osteoarthritis (8), carpal tunnel syndrome (10), and musculoskeletal disorders (15). Even in these cases, results show it is a treatment with potential modest beneficial effects. By modest I mean that the meta-analysis on LLLT effect on osteoarthritis showed it may be helpful for short term relief of pain and morning stiffness, not more (8).

It has also shown some promising adjuvant treatment efficacy for maxillofacial post surgical recovery (13, 17).

Authors stress that although the mechanisms are unknown, all results are probably related to anti-inflammatory effect, possibly to local heat application. Effect is frequently considered “modest”.

Does red light therapy increase metabolism?

That’s a basic claim, presented everywhere from peer reviewed studies, through popularization articles and even advertisement pieces: red light therapy boosts metabolism. That claim is based on a study about the effect of red light over isolated mitochondria (20) and one (equally in vitro) study indicating that “the relevant chromophore” for the absorption of LLLT’s photons is cytochrome c oxidase (26). A chromophore is the part of a molecule that causes a conformational change in its structure when hit by light.

The first study, published by Greco and collaborators (20), described the increase in RNA and protein synthesis on mitochondria isolated according to the standard method introduced by Klingenbert and Slencza in 1959. The second one is so obscure that I couldn’t find the original paper to examine.

Mitochondria are the cellular organelles where a process called oxidative phosphorylation takes place. That is the metabolic pathway where the highest number of ATP molecules is produced. Cytochrome c oxidase is the last enzyme in the oxidative phosphorylation chain. Higher mitochondrial activity in vivo is a by-proxy indication of increased energy metabolism.

However, whatever happens in the isolated organelle cannot be automatically generalized to intact tissues or to living organisms. But that is just one of the problems with this argument. There is no direct evidence that Cytochrome c oxidase is the “relevant chromophore” for anything related to LLLT.

Okay, let’s show an image of this (because it is beautiful) and give you the bottom line: even if something is observed on real molecules or organelles (functional structures of cells), on a Petri dish (“in vitro”), researchers may not generalize that to anything happening at the muscle, heart, liver or, worse, the whole person.

Fig 5 – a. Animal mitochondrion (40), b. the electron transport chain or oxidative phosphorylation (Fvasconcellos 2007) and c. a molecular model of the Cytochrome c oxidase (12)

Does red light therapy increase metabolism? We can’t say it does not. Hot packs over a body part increases blood flow and we could say it increases metabolism in general (including possibly increasing inflammation and infection). But to claim that red light therapy increases metabolism because of in vitro experiments on isolated mitochondria and cells (and even bacteria, as suggested by Karu 1987) is a bit of a stretch.

Does red light therapy help repair wounds of damaged tissue?

Again, maybe: all studies indicating this effect were performed in animal models or in vitro cell studies (32, 6, 37).

Wound repair of damaged tissue basically involves migration of fibroblasts, which are the cells responsible for “patching up” broken tissue. They are versatile cells that can migrate to damaged areas, reproducing and synthesizing extracellular matrix and collagen (the “glue” that binds cells together).

What research into LLLT and wound repair has shown is that it can influence fibroblast migration and collagen synthesis in vitro and in animal models. Therefore, we still don’t know what the mechanism of action is.

Should you use it? If it is a cheap device you will be using at home, why not? After all, research shows “it may help”. But if you are going to pay for a non-FDA approved treatment at a clinic that your insurance will not cover, you might consider the traditional treatment options that are proved to work first.

Does red light therapy help immune function?

Direct evidence for immune stimulating effect of red light therapy was obtained in animal models and the focus of research has been acute inflammatory response rather than actual immune function changes (23). Until there is evidence for its effect in humans, you’d better not consider this option.

Does red light therapy reduce side effects of cancer treatments?

LLLT is a moderately beneficial adjuvant therapy for cancer treatment side effects because it is relatively useful in wound healing. Since some of the painful side effects of cancer treatment, especially chemotherapy, are epithelial wounds, which is where LLLT shows some promising application (45, 25 and 35).

If you are undergoing chemotherapy and external wound healing is an issue, you may try to use LLLT if you have a cheap device that can be used at home and your doctor is fine with this. Remember: it is not a FDA approved treatment and research is still controversial.

Does red light therapy reduce signs of skin aging?

And here we land at the application of LLLT that is probably responsible for the fad that grew around it in recent years. So: is it or is it not a “rejuvenating” agent? Yes, it seems to have beneficial effect. But then, anything seems to have beneficial effect: the first study I examined compared light therapy with two different light frequency and spectra, concluding both worked (42).

The second study compared radiofrequency (RF), electroacupuncture (EA), and low-level laser therapy (LLLT), concluding all of them were beneficial (28). If anything works, why would you choose the least consensual of the treatment options?

The least we can say here is that more research is needed until we can say anything about the benefits of red light therapy for rejuvenation.

Is red light therapy helpful for hair loss?

The most recent meta-analysis of studies concerning LLLT for hair loss states that data is inconclusive “because there was a lack of visual evidence, sample sizes were low, and there were large variations in study duration and efficacy measurements” (21). Another recent review (44) found methodological problems as well, but concluded it is a safe method and effective in some cases.

Hair loss treatment is always long term, frequently frustrating. Maybe you are better off with the approved treatment options that are still much cheaper than LLLT applied at a specialized clinic. Research compares LLLT treatment with minoxidil, for example, which is an over-the-counter topical medication with proved beneficial effect for hair loss.

Does red light therapy help arthritis?

That is the one case in which research provides a clear cut answer: yes, it does. It helps patients with rheumatoid arthritis with short-term treatment for relief of pain and morning stiffness, and that’s it (8).

I’d say go for it. Arthritis is painful and long-term. Anything that provides you with a little relief for the constant pain this condition causes is worth using, even if the effect is short term and modest. You can find red light lamps and devices for that purpose for less than $100.00. Mine lasted for 20 years.

Does red light therapy help depression?

The relationship between light and depression was evidenced when a condition called “seasonal affective disorder” was identified in 1984 (36). A percentage of the human population displays a seasonal pattern of depression or anxiety which, it is believed, is related to daylight variations. From start, light therapy was considered a route to be pursued.

Research shows that exposure to morning light produces benefits to patients and that “light therapy” is effective (39). Another study showed that bright light therapy may be beneficial to depression in general, regardless of whether it is seasonal or not (33).

Since in the 1980s it was believed that it was the blue component in daylight that was effective in the treatment of seasonal affective disorders, this hypothesis was tested and rejected: apparently, any light is beneficial (5).

So, is red light therapy good for depression? Maybe (Cassano et al 2016). But so is any light, as more solid research shows.

My advice: don’t self-medicate, especially with unproven methods. Talk to a licensed psychiatrist. If you and him decide light is interesting, a morning walk outdoors may be more beneficial.

Does red light increase testosterone?

This seems to be a very exciting non-result for LLLT: 2.2 million entries from a google search and not a single published scientific article. All this hype comes from a paper presented at a European Neuropsychology congress (30). The study was performed with 38 males suffering from decreased libido, who were subject to “bright light therapy” (not red light therapy).

An increase in testosterone from around 2.1 ng/ml to 3.6 ng/ml was observed in two weeks. Another study conducted on rams was inconclusive (4).

If you are suffering from lack of sexual desire and you are hesitant concerning hormone replacement, science suggests, again, that maybe a daily walk on the park might be helpful.

Are there side effects to red light therapy?

One thing that can be said about red light therapy or LLLT is that it is safe. It may not help with your condition, but it won’t make it worse. There is no indication that you may suffer any side effects from it.


Red light therapy has been used for decades, and for decades it has been proved useful. The question is what it is useful for. It seems that the claims that it has mysterious molecular properties and that its panaceaic effects are a result of those are unfounded. The panaceaic effects, themselves, seem to be overstated.

Red light therapy is helpful with pain and inflammation, as it has been used from the beginning. More than that, there is not only no consistent evidence, but no real mechanism to support the claims.

Does that mean we shouldn’t use it? No: it means it is an interesting device for pain, joint and musculoskeletal inflammation and a few other inflammatory conditions. It is safe, cheap and devoid of side effects, as compared to other therapeutic strategies.

Use it wisely.


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