Cold Laser Therapy (LLLT): Uses, Benefits, and What the Research Shows

You have probably seen cold laser therapy mentioned alongside other regenerative treatments at physical therapy clinics, sports medicine offices, and integrative health practices. It has been around for decades, used everywhere from NASA research labs to professional sports training rooms. But separating the real science from the marketing hype can be tricky.

So what does cold laser therapy actually do? Which conditions does it help? And what does the published research say?

This article breaks it all down, from the cellular mechanisms to the clinical evidence, so you can make an informed decision about whether this therapy belongs in your recovery plan.

What Is Cold Laser Therapy?

Cold laser therapy, formally known as low-level laser therapy (LLLT) or photobiomodulation (PBM), uses specific wavelengths of light to stimulate healing and reduce pain and inflammation in damaged tissues [1]. The term “cold” distinguishes it from high-power surgical lasers that cut tissue. Cold lasers do not generate significant heat, and you typically feel nothing, or at most a mild warmth, during treatment.

The therapy uses light in the red (630 to 670 nm) and near-infrared (810 to 980 nm) wavelength ranges, delivered at low power densities. These wavelengths can penetrate skin and soft tissue to reach cells, where they trigger a chain of biological responses [2].

The first clinical applications of low-level laser therapy date back to 1967, when Hungarian physician Endre Mester observed that low-power laser light accelerated hair growth and wound healing in mice. Since then, thousands of studies have investigated its effects on pain, inflammation, tissue repair, and neurological conditions [3].

How Cold Laser Therapy Works: The Mechanism of Action

Understanding how photobiomodulation works at the cellular level helps explain both its benefits and its limitations.

The Mitochondrial Connection

The primary target of cold laser light is cytochrome c oxidase (CCO), an enzyme within the mitochondrial electron transport chain. When photons of the right wavelength are absorbed by CCO, several things happen [4]:

The Biphasic Dose Response

One of the most important concepts in cold laser therapy is the Arndt-Schulz principle, or biphasic dose response. Too little light has no effect. The right dose stimulates healing. Too much light can actually inhibit cellular function [2]. This is why proper dosing, including wavelength, power density, treatment time, and total energy delivered, matters so much. A poorly calibrated device or incorrect treatment protocol can produce underwhelming results, which partly explains the inconsistent outcomes seen in some older studies.

Conditions Treated with Cold Laser Therapy

Research has investigated cold laser therapy for a wide range of conditions. Here are the areas with the strongest evidence.

Musculoskeletal Pain

Pain relief is the most common clinical application of cold laser therapy, and the evidence here is substantial.

A 2010 systematic review in The Lancet analyzed 16 randomized controlled trials involving 820 patients with chronic neck pain. LLLT significantly reduced pain immediately after treatment and up to 22 weeks later compared to placebo [7].

For osteoarthritis, a 2019 meta-analysis in Lasers in Medical Science found that PBM significantly reduced pain and improved functional outcomes in knee osteoarthritis, with effects that were sustained over follow-up periods of 4 to 12 weeks [8].

Low back pain has also been studied, with a 2015 meta-analysis in PLOS ONE reporting that LLLT provided short-term pain relief and functional improvement in patients with chronic low back pain, though the authors noted the need for more standardized protocols [9].

Tendinopathies

Tennis elbow (lateral epicondylitis), Achilles tendinopathy, and other tendon disorders respond well to cold laser therapy when proper dosing parameters are used. A 2014 systematic review found that LLLT combined with exercise produced better outcomes for tendinopathy than either intervention alone [10].

Inflammation

Cold laser therapy has strong anti-inflammatory effects that operate through multiple pathways. It reduces pro-inflammatory cytokines (including TNF-alpha, IL-1 beta, and IL-6), decreases edema, and modulates immune cell activity [6]. This makes it useful not only for musculoskeletal inflammation but also for inflammatory conditions affecting other tissues.

Wound Healing and Tissue Repair

PBM accelerates wound healing by stimulating fibroblast proliferation, increasing collagen synthesis, and promoting angiogenesis (the formation of new blood vessels) [3]. Clinical applications include:

• Diabetic ulcers
• Post-surgical wound healing
• Burns
• Oral mucositis (a painful side effect of chemotherapy and radiation)

For oral mucositis specifically, the evidence is strong enough that clinical guidelines from organizations including the Multinational Association of Supportive Care in Cancer (MASCC) recommend PBM for prevention [11].

Hair Loss

Endre Mester’s original 1967 observation about laser-stimulated hair growth has been confirmed by modern research. Low-level laser therapy is FDA-cleared for androgenetic alopecia (pattern hair loss) in both men and women.

A 2014 randomized, double-blind, sham-controlled trial published in the American Journal of Clinical Dermatology found that LLLT devices significantly increased hair density compared to sham devices over a 26-week treatment period [12]. The mechanism appears to involve stimulation of hair follicle stem cells, increased blood flow to the scalp, and a shift of follicles from the telogen (resting) to anagen (growth) phase.

Neuropathy and Nerve Injuries

Emerging research suggests cold laser therapy may benefit peripheral neuropathy and nerve injuries. A 2017 study in Lasers in Medical Science found that PBM improved nerve conduction velocity and reduced pain in patients with diabetic peripheral neuropathy [13]. Animal studies have also demonstrated accelerated nerve regeneration after injury with appropriate laser parameters.

Temporomandibular Joint Disorders (TMJ)

Several systematic reviews support the use of LLLT for TMJ-related pain, with improvements in mouth opening capacity and reduction in pain scores [14].

What a Cold Laser Therapy Session Looks Like

If you have never had a cold laser session, here is what to expect.

Before the Session

The practitioner will assess your condition, identify the treatment area, and select the appropriate device and protocol. No special preparation is needed on your part. You do not need to fast or avoid any activities beforehand.

During Treatment

You will be positioned comfortably, usually sitting or lying down. The practitioner applies the laser device directly to the skin over the treatment area. Depending on the device, this might be a small handheld probe or a larger panel with multiple diodes.

A typical session lasts 5 to 20 minutes per treatment area. You will feel little to nothing during the treatment. There is no pain, no vibration, and usually no sensation at all. Some patients report a mild warmth, particularly with near-infrared wavelengths.

Eye protection is standard practice, as direct laser exposure to the eyes must be avoided.

After Treatment

There is no downtime. You can return to normal activities immediately. Some patients notice pain relief within the first session, while others require several treatments before noticing improvements. A typical treatment course consists of 8 to 12 sessions, often scheduled 2 to 3 times per week.

At-Home Devices

Consumer-grade cold laser and LED devices are available for home use. These range from handheld laser devices to wearable LED pads and helmet-style devices for hair loss. While some of these products are FDA-cleared and backed by research, many are underpowered or use wavelengths that are not well supported by evidence. If you are considering a home device, look for one that specifies its wavelength (ideally 630 to 670 nm or 810 to 980 nm), power output, and energy density. Consulting with a knowledgeable practitioner before purchasing can save you from wasting money on an ineffective device.

Safety and Side Effects

Cold laser therapy has an excellent safety profile. The most common “side effect” is simply no response, usually due to inadequate dosing.

Serious adverse events are rare. A 2023 review of the safety literature found that LLLT is well tolerated across a wide range of conditions and patient populations [15]. However, there are a few precautions:

• Pregnancy. Cold laser therapy is generally avoided over the abdomen during pregnancy, though there is no direct evidence of harm.
• Cancer. Direct application over known tumors is typically avoided due to theoretical concerns about stimulating cell proliferation, though research in this area is evolving.
• Photosensitivity. Patients taking photosensitizing medications should discuss this with their practitioner.
• Eyes. Direct laser exposure to the eyes must always be avoided. Protective eyewear is standard.
• Epilepsy. Transcranial PBM should be used with caution in patients with seizure disorders.

There are no known drug interactions, and cold laser therapy can be safely combined with most other treatments, including physical therapy, chiropractic care, and medications.

What the Critics Say

Despite a large body of supportive research, cold laser therapy still faces skepticism in some quarters. The main criticisms include:

Inconsistent study results. Early LLLT studies used widely varying parameters, making it difficult to compare outcomes across trials. Many negative studies used suboptimal doses or inappropriate wavelengths [2]. More recent research using standardized parameters has produced much more consistent results.

Placebo effect. As with any therapy, some benefit may be attributable to placebo. However, multiple sham-controlled trials have demonstrated statistically significant effects beyond placebo, particularly for pain and inflammation [7][8].

Mechanism complexity. The biphasic dose response means that getting the parameters right is essential. This complexity means that not every practitioner achieves optimal results, even with a sound therapeutic modality.

How to Get the Most from Cold Laser Therapy

If you decide to pursue cold laser therapy, keep these points in mind:

When to See a Doctor

Cold laser therapy is appropriate for many musculoskeletal and inflammatory conditions, but it is not a substitute for a proper medical evaluation. See a physician if you experience:

• Sudden, severe, or unexplained pain
• Signs of infection (redness, warmth, swelling, fever)
• Symptoms of nerve damage such as numbness, weakness, or loss of bowel/bladder control
• Pain that worsens despite treatment
• Any new or unexplained symptoms

If you have a diagnosed condition and are considering adding cold laser therapy to your treatment plan, discuss it with your primary care provider or specialist. Most physicians are open to complementary therapies that have a reasonable evidence base and good safety profile.

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References

[1] Chung, H., Dai, T., Sharma, S. K., Huang, Y. Y., Carroll, J. D., & Hamblin, M. R. (2012). The nuts and bolts of low-level laser (light) therapy. Annals of Biomedical Engineering, 40(2), 516-533. PMID: 22045511

[2] Huang, Y. Y., Chen, A. C., Carroll, J. D., & Hamblin, M. R. (2009). Biphasic dose response in low level light therapy. Dose-Response, 7(4), 358-383. PMID: 20011653

[3] de Freitas, L. F., & Hamblin, M. R. (2016). Proposed mechanisms of photobiomodulation or low-level light therapy. IEEE Journal of Selected Topics in Quantum Electronics, 22(3), 7000417. PMID: 28070154

[4] Karu, T. I. (2008). Mitochondrial signaling in mammalian cells activated by red and near-IR radiation. Photochemistry and Photobiology, 84(5), 1091-1099. PMID: 18651871

[5] Hamblin, M. R. (2018). Mechanisms and mitochondrial redox signaling in photobiomodulation. Photochemistry and Photobiology, 94(2), 199-212. PMID: 28949040

[6] Hamblin, M. R. (2017). Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS Biophysics, 4(3), 337-361. PMID: 28748217

[7] Chow, R. T., Johnson, M. I., Lopes-Martins, R. A., & Bjordal, J. M. (2009). Efficacy of low-level laser therapy in the management of neck pain: A systematic review and meta-analysis of randomised placebo or active-treatment controlled trials. The Lancet, 374(9705), 1897-1908. PMID: 19913903

[8] Stausholm, M. B., Naterstad, I. F., Joensen, J., Lopes-Martins, R. A. B., Saebø, H., Lund, H., … & Bjordal, J. M. (2019). Efficacy of low-level laser therapy on pain and disability in knee osteoarthritis: Systematic review and meta-analysis of randomised placebo-controlled trials. BMJ Open, 9(10), e031142. PMID: 31594900

[9] Huang, Z., Ma, J., Chen, J., Shen, B., Pei, F., & Kraus, V. B. (2015). The effectiveness of low-level laser therapy for nonspecific chronic low back pain: A systematic review and meta-analysis. Arthritis Research & Therapy, 17(1), 360. PMID: 26667480

[10] Tumilty, S., Munn, J., McDonough, S., Hurley, D. A., Basford, J. R., & Baxter, G. D. (2010). Low level laser treatment of tendinopathy: A systematic review with meta-analysis. Photomedicine and Laser Surgery, 28(1), 3-16. PMID: 19708800

[11] Zadik, Y., Arany, P. R., Fregnani, E. R., Bossi, P., Antunes, H. S., Bensadoun, R. J., … & Lalla, R. V. (2019). Systematic review of photobiomodulation for the management of oral mucositis in cancer patients and clinical practice guidelines. Supportive Care in Cancer, 27(10), 3969-3983. PMID: 31286228

[12] Lanzafame, R. J., Blanche, R. R., Bodian, A. B., Chiacchierini, R. P., Fernandez-Obregon, A., & Kazmirek, E. R. (2013). The growth of human scalp hair mediated by visible red light laser and LED sources in males. Lasers in Surgery and Medicine, 45(8), 487-495. PMID: 24078483

[13] Yamany, A. A., & Sayed, H. M. (2012). Effect of low level laser therapy on neurovascular function of diabetic peripheral neuropathy. Journal of Advanced Research, 3(1), 21-28. PMID: 25750070

[14] Maia, M. L., Bonjardim, L. R., Quintans Jde, S., Ribeiro, M. A., Maia, L. G., & Conti, P. C. (2012). Effect of low-level laser therapy on pain levels in patients with temporomandibular disorders: A systematic review. Journal of Applied Oral Science, 20(6), 594-602. PMID: 23329239

[15] Cotler, H. B., Chow, R. T., Hamblin, M. R., & Carroll, J. (2015). The use of low level laser therapy (LLLT) for musculoskeletal pain. MOJ Orthopedics & Rheumatology, 2(5), 00068. PMID: 26858986