Many of the big commercial fads today are related to the skin care industry.

In an aging world, or in a world where actual consumers are proportionately older, nothing is commercially hotter than anti aging. If you start to worry about your wrinkles, or your collagen levels, or your eye skin, neck skin, or mouth skin, there’s an army of hip-looking websites and blogs waiting to console you.

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 them 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”, “healing”, “skin care” and “energy”. Red “light+anti-aging” alone renders 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 tissue repair, immune boosting, collagen production, 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 collaborators (22) suggest, it was the non-invasiveness and patient acceptance of red light treatment that keeps it in use, in spite of not being FDA approved or covered by insurance companies. What could 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 actually says about the effectiveness of red light therapy [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 skin 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 red light 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 on the opposite side of the visible light spectrum and have very different interactions 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 on in the following sections, 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?

The short answer is that for the past 5 years there have averaged more than 200 published articles a year on red light therapy

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).

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

Examining the peer-reviewed original research publications and reviews on red light therapy, raised the following red flags:

  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 red light 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 red light 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 red light 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 red light 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 support 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 red light effects 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 red light’s effect on osteoarthritis showed it may be helpful for short term relief of joint pain and morning stiffness, not more (8).

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

The authors stress that although the mechanisms are unknown, all results are probably related to the anti-inflammatory effect, possibly to local heat application. The 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 (with the inference that it should then be helpful for weight loss). 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 red light 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 in 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 red light therapy.

Is red light therapy effective at increasing metabolism? We can’t say it is not. Hot packs over a body part increase 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 heal wounds or damaged tissue?

Now that collagen is such a hot topic, we get to see two fads combining forces.

The answer to whether red light therapy has wound healing properties is again, maybe: all studies indicating a healing effect were performed in animal models or in vitro cell studies (32, 6, 37).

The healing of damaged tissue basically involves the 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 red light therapy and wound healing 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. Note, however, this is different from “collagen production” which many websites claim red light therapy can induce.

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 proven to be effective first.

Does red light therapy help immune function?

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

Does red light therapy reduce the side effects of cancer treatments?

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

If you are undergoing chemotherapy and external wound healing is an issue, you may try to use red light therapy if you have a cheap device that can be used at home and your doctor is fine with this. Remember: it is not an 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 red light that is probably responsible for the fad that grew around it in recent years. So: is it or is it not a skin rejuvenating agent?

Yes, it seems to have a beneficial effect. But then, lots of things seem to be effective: the first study I examined compared infrared light therapy with two different light frequencies 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 infrared light for skin 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. The research compares LLLT treatment with minoxidil, for example, which is an over-the-counter topical medication with a 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 it’s only effective in the short term and the effects are 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 effective 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 they 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 red light: 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 a lack of sexual desire and you are hesitant concerning hormone replacement, science suggests, again, that maybe a daily walk in 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.

Conclusion

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 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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