Photobiomodulation therapy (PBMT) is the use of light as a medical treatment. “Cold” or low-level laser therapy (LLLT) is the best-known specific type of PBMT, but it’s not a great term, just a customary one.1 Laser light is only one of many riffs on PBMT tune. For instance, even tanning beds could be considered one form of PBMT (to stimulate vitamin D production). Far-infrared saunas are advertised like they beam healing rays.2 But I will speak mostly of “lasers” in this article, because it’s fun and half-right.
Lasers seem to attract cranks and quacks, and laser therapy is strongly associated with much more than its fair share of bullshit and fraud. Skeptical appraisals of laser therapy are harsh.3 According to the people selling cold laser treatments, there’s almost no limit to the conditions that will benefit from laser therapy, and the internet is awash with images like this:
A “chart” showing the conditions laser therapy is supposedly good for, which apparently is basically anything you can name, including several that are notoriously impossible to treat.
The big idea is that lasers can supposedly stimulate healing (as opposed to, you know, burning a hole in you like a starship trooper). They are intended to help damaged tissue recover faster, or finish recovering when it’s struggling to. It is not just a pain treatment, and it’s not about heating tissues at all (one reason it’s often called “cold” laser therapy).4 If it works, it’s a big deal.
It would be such a big deal that one might ask: where is the Nobel prize for that?5 I’ve been doing this job long enough to know that, if a treatment was genuinely promising and legit, I probably would’ve heard about it long ago. The WHAILO principle!6 I appreciate that legitimately interesting medicine can cruise along in obscurity for a long-time for many reasons, but the effects claimed for lasers are truly amazing. These are perfect examples of the “extraordinary claims” that Sagan famously said require “extraordinary evidence.”
Actually, it’s hard to think of an example of any technological therapy that has panned out.
But laser therapy has its fans, of course! And its inevitable “promising” evidence of dubious value.
I had to include this, obviously. One simply cannot speak of lasers without this pop culture reference.
The not-actually-promising evidence
An educated reader brought this paper to my attention, hoping to persuade me to take laser therapy seriously. In 2014, Alves et al published a glowing review of 17 papers about LLT specifically for the “short-term” treatment of muscle injuries.8 They found that it reduced inflammation, and stimulated the growth of new blood vessels, and improved muscle recovery. They called it an “excellent therapeutic resource for the treatment of skeletal muscle injuries.” This sounds very good. And does indeed appear to be the best scientific review of this topic to date.
There’s a catch, though. Seems like there always is.
Animals only! They were only reviewing animal studies, because animal studies are the only studies to review. As of 2018, there is still not even one human trial (for muscle strain specifically). Obviously animal studies are not adequate. What works on other animals routinely fails with human animals and vice versa.
There is basically just no persuasive clinical science on this topic. There is (of course) lots of low-quality evidence showing mixed and trivial effects9 — that’s just standard these days. The lack of quality evidence does not mean it doesn’t work, but it does damn laser therapy with faint praise and highlight a suspicious failure so far to produce better evidence. And it means that laser therapy cannot yet be considered evidence-based — it can only be hope-based. All we can do is try to rationally evaluate the plausibility, costs, and risks.
How likely is it that lasers stimulate healing? In humans?
There is a clear biological response of human skin to UV radiation: it makes vitamin D, which is quite important to us. This is the main template for all other ideas photobiomodulation. A few other biological effects of light have been confirmed over the decades, like its role in regulating circadian rhythms. There are photosensitive proteins. Light does affect biology.10
So what else might light do to us? What about radiation on different parts of the EM spectrum? What about “coherent” (laser) light?
Could light … heal? Could lasers? It’s not clear why anyone would suspect that specifically based on what is known about the effects of light. I think it’s a nearly perfect unknown. I am not aware of any specific reason to think that laser can facilitate healing.
But I can think of a reason why it wouldn’t. The hopes of all kinds of regenerative medicine are all pinned on the grand idea that biology has potential for improved healing that can be “unlocked.” But this is broadly implausible. Biology doesn’t really have many valuable hidden features that only emerge with an exotic/rare stimulus: either a system didn’t evolve in the first place, or it did and we’re already using it.
But biology is also insanely complex, so who knows?
This is just one of those things that we’ll simply have to test — more thoroughly and much better than we have so far.
Laser therapy costs
Costs or laser therapy gadgets for home use range widely, but tend to be higher than other related gadgets (TENS, PEMF, ultrasound, etc). A typical one is well over a hundred bucks. Anyone selling laser therapy in a clinic is likely to heap scorn on the DYI approach, because they like you to pay them by the session. As with all such services, repeated applications and package “deals” are the normal, and the total price tag is non-trivial: probably less than massage, but with virtually no potential side benefits.
Laser therapy risks
Lasers certainly can be dangerous if used improperly. Obviously. •pew pew!•
In practice, commercially available PBMT gadgets are mostly working with such low energies that the risk is probably very low even if used improperly. On the other hand, there are many products with widely ranging features … and some really sketchy people selling laser therapy. I have no hard safety data, but with so many devices and so many sketchy providers, there is probably some risk.
Here be cranks!
Like “quantum” and “toxins,” lasers sound cool. They are a great marketing tool. The way laser therapy is advertised and used in the wild does raise a lot of red flags and makes it a lot harder to separate sense and nonsense.
For instance, consider the claim that laser therapy for trigger points works because it “energizes the damaged cells.” That was stated by someone who trains trigger point therapists. It’s really crazy, but it’s a common claim made by laser therapy mongers. It’s not even defensible as an informal, dumbed down explanation of anything, because there’s no more complicated version to simplify. It’s just pure nonsense that has nothing to do with actual biology, a classic example of “not even wrong.” It’s so ridiculous that I wouldn’t even bring it up if it weren’t actually representative of laser therapy claims. And it’s not even the worst!
An even more ridiculous laser therapy claim reported by someone else: it “kickstarts photosynthesis in human cells”! That’s not even close to an actual thing, of course, because humans aren't plants and we don't do photosynthesis, ever.
When people are talking like this about laser therapy, it’s a lot harder to take it seriously.
Laser therapy has a nasty frickin’ theory versus practice problem:
- Theory: There’s some legitimately intriguing basic science observations about the effects of light/lasers on biology, and in a perfect world these effects would be investigated systematically and rationally over many years and, someday, they might lead somewhere clinically useful.
- Practice: Laser therapy is embraced and sold almost exclusively by the ignorant and profiteering, none of whom really have clue if they are using the right kind of lasers in the right way on the right tissues, and if there’s any real healing effect it’s probably only happening by fluke in a few cases.
In the real world, I don’t think laser therapy reaches the threshold required for being “worth a shot” — not even if you’re desperate, not even if you can easily afford it. Although safe and plausible in an anything’s-possible way, it’s just too much of a long shot to be worth a shot. By far the most likely result is that you simply waste your time and transfer some of your wealth to someone who doesn’t deserve it.
About Paul Ingraham
I am a science writer, former massage therapist, and I was the assistant editor at ScienceBasedMedicine.org for several years. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook or Twitter.
- Salamander and Regeneration Science — Why does PainScience.com have a salamander mascot? Their regenerative superpower is an inspiring, profound example of what is possible in biology and healing
- Does Platelet-Rich Plasma Injection Work? — An interesting treatment idea for arthritis, tendinopathy, muscle strain and more
- Does Cartilage Regeneration Work? — A review of knee cartilage “patching” with autologous chondrocyte implantation (ACI)
- Zapped! Does TENS work for pain? — The peculiar popularity of being gently zapped with electrical stimulation therapy
- Does Ultrasound Therapy Work? — Many concerns about the widespread usage of therapeutic ultrasound, especially extracorporeal shockwave therapy (ESWT)
- Heat for Pain — A detailed guide to using heat as therapy for acute and chronic pain. The discussion of infrared radiation particularly relevant.
What’s new in this article?
2018 — Added footnote about new Nobel prizes for laser technology, and how it has already been exploited to sell cold laser therapy.
- Anders JJ, Lanzafame RJ, Arany PR. Low-level light/laser therapy versus photobiomodulation therapy. Photomed Laser Surg. 2015 Apr;33(4):183–4. PubMed #25844681 ❐ PainSci #53021 ❐ “In addition to biostimulation, a few of the other names previously used for this therapy have included low-level laser (or light) therapy (LLLT), low-intensity laser therapy, low-power laser therapy, cold laser, soft laser, photobiostimulation, and photobiomodulation.”
- Infrared radiation is basically synonymous with “heat.” Far-infrared radiation is the part of the infrared section of the electromagnetic spectrum with the longest wavelengths, and it is widely touted to penetrate at least a few centimetres into tissue; the citation usually given for this (if any) does not actually support the claim. Effects on biology beyond simply warming tissues are conceivable, but have never actually been documented. I explore this topic in more detail in my thermotherapy article: Heat for Pain: A detailed guide to using heat as therapy for acute and chronic pain.
- www.devicewatch.org [Internet]. Barrett S. A Skeptical Look at Low Level Laser Therapy; 2018 Apr 26 [cited 18 Sep 24].
- Anders JJ, Lanzafame RJ, Arany PR. Low-level light/laser therapy versus photobiomodulation therapy. Photomed Laser Surg. 2015 Apr;33(4):183–4. PubMed #25844681 ❐ PainSci #53021 ❐ “The use of this term is key, as it distinguishes photobiomodulation therapy, which is nonthermal, from the popular use of light-based devices for simple heating of tissues as can be accomplished using near-infrared (NIR) lamps, or other applications of light energy that rely on thermal effects for all or part of their mechanism of action.”
- Multiple Nobel prizes have been awarded for the medical uses of lasers — see the Ashkin, Mourou, Strickland 2018 prizes for “optical tweezers” and short and intense laser bursts with many medical applications. These are not prizes for photobiomodulation. But that didn’t stop one cold laser therapy brand from strongly implying with a Facebook post that these Nobel prizes were relevant. To be fair, they didn’t actually say it was the same kind of laser application, and the post could easily be interpreted as general enthusiasm for laser technology. But, shocker, they didn’t go out of their way to explain that the Nobel prizes were awarded for completely different technology than cold laser therapy. 😜 Obviously this news is going to be exploited to help sell cold laser therapy.
- Which should be getting more potent as I age. Another decade of this and I won’t have to critically evaluate any claim!
- For example, tanning beds really do stimulate vitamin D production — a genuine, interesting, useful biological effect of shining light on people — but there’s a list of practical problems that makes using them a really terrible idea. And those problems have only become clear after decades of the technology being widely used! See Woo and or my vitamin D article for much more information.
- Alves AN, Fernandes KP, Deana AM, Bussadori SK, Mesquita-Ferrari RA. Effects of low-level laser therapy on skeletal muscle repair: a systematic review. Am J Phys Med Rehabil. 2014 Dec;93(12):1073–85. PubMed #25122099 ❐
- Crislip, Mark. Low Level Lasers: N-Rays in action. ScienceBasedMedicine.org. August 24, 2012. “Like acupuncture, there is a huge literature (4000 on the Pubmeds) of mostly poorly done studies, some showing effect, some not. The Cochrane reviews were not supportive of laser therapy, but note the studies are uniformly lousy.”
- Editors. The light fantastic. Nat Chem Biol. 2014 Jul;10(7):483. PubMed #24937055 ❐ PainSci #52994 ❐