Low-level laser therapy (LLLT), cold laser therapy, photobiomodulation (PBM)[1][2][3][4] or red light therapy[5] is a form of
medicine that applies low-level (low-
power)
lasers or
light-emitting diodes (LEDs) to the surface of the body. Whereas high-power lasers are used in
laser medicine to cut or destroy tissue, it is claimed that application of low-power lasers relieves pain or stimulates and enhances cell function. The effects appear to be limited to a specified set of wavelengths and new research has demonstrated effectiveness at myopia control.[6] Several such devices are cleared by the
United States Food and Drug Administration (FDA), and research shows potential for treating a range of medical problems including
rheumatoid arthritis[7] and
oral mucositis.[8]
Mechanism
This section needs expansion. You can help by
adding to it. (June 2023)
Research is ongoing about the mechanism of LLLT. The effects of LLLT appear to be limited to a specified set of wavelengths of laser,[9] and administering LLLT below the dose range does not appear to be effective.[10]Photochemical reactions are well known in biological research, and LLLT make use of the first law in photochemistry (
Grotthuss-Draper law): light must be absorbed by a chemical substance in order for a photochemical reaction to take place. In LLLT that chemical substance is represented by the respiratory enzyme
cytochrome c oxidase which is involved in the
electron transport chain in
mitochondria,[11][12] which is the generally accepted theory.
Veterinary clinics use cold laser devices to treat a wide variety of ailments, from arthritis to wounds, on dogs and cats.[21][22] Very little research has been done on the effects of this treatment on animals. Brennen McKenzie, president of the
Evidence-Based Veterinary Medicine Association, has stated that "research into cold laser in dogs and cats is sparse and generally low quality. Most studies are small and have minimal or uncertain controls for bias and error".[23][24] While allowing that some studies show promising results, he reports that others do not. While believing that there is enough evidence to warrant further study, he concludes that there is not enough evidence to support routine clinical use of cold laser in animals.
Hungarian physician and surgeon
Endre Mester (1903–1984) is credited with the discovery of the biological effects of low power lasers,[28] which occurred a few years after the 1960 invention of the
ruby laser and the 1961 invention of the
helium–neon (HeNe) laser.[11] Mester accidentally discovered that low-level ruby laser light could regrow hair during an attempt to
replicate an experiment that showed that such lasers could reduce tumors in mice. The laser he was using was faulty and wasn't as powerful as he thought. It failed to affect the tumors, but he noticed that in the places where he had shaved the mice in order to do the experiments, the hair grew back more quickly on the treated mice than on those among the control group.[2] He published those results in 1967.[11] He went on to show that low level HeNe light could accelerate wound healing in mice.[11]
By the 1970s, he was applying low level laser light to treat people with
skin ulcers.[11] In 1974, he founded the Laser Research Center at the
Semmelweis Medical University in
Budapest, and continued working there for the remainder of his life.[29] His sons carried on his work and brought it to the United States.[28] By 1987, companies selling lasers were claiming that they could treat pain, accelerate healing of sports injuries, and treat arthritis, but there was little evidence for this at that time.[28] Mester originally called this approach "laser biostimulation'", but it soon became known as “low-level laser therapy" and with the adaptation of
light emitting diodes by those studying this approach, it became known as "low-level light therapy", and to resolve confusion around the exact meaning of "low level", the term "photobiomodulation" arose.[2]
Names
The following terms are accepted as alternatives of low level light therapy term: LLLT, laser biostimulation, laser phototherapy, low-level laser therapy, low-power laser irradiation, low-power laser therapy, and photobiomodulation therapy. The term photobiomodulation therapy is considered the preferred term by industry professionals.[3][4] However LLLT has been marketed and researched under a number of other terms, including red light therapy,[30] low-power laser therapy (LPLT), soft laser therapy, low-intensity laser therapy, low-energy laser therapy, cold laser therapy, bio-stimulation laser therapy, photo-biotherapy, therapeutic laser, and monochromatic infrared light energy (MIRE) therapy.[31] More specific applications sometimes have their own terms, for example when administered to acupuncture points, the procedure is called laser acupuncture. When applied to the head, LLLT may be known as transcranial photobiomodulation, transcranial near-infrared laser therapy (NILT),[32] or transcranial low level light therapy.
Government action
The FDA filed a complaint for injunction in 2014, alleging that company QLaser PMA were marketing their devices as being able to treat “over 200 different diseases and disorders,” including cancer, cardiac arrest, deafness, diabetes, HIV/AIDS, macular degeneration, and venereal disease. This case resulted in a permanent injunction against the manufacture, marketing, sale, and distribution of those devices in 2015.[33]
In 2017, the owner of QLaser, Robert Lytle, and two of QLaser's distributors were charged with a criminal conspiracy to commit fraud. Lytle pleaded guilty to one count of conspiracy to introduce misbranded medical devices into interstate commerce with the intent to defraud and mislead, and one count of criminal contempt in January 2018. Lytle was sentenced to serve 12 years in prison and made an initial restitution payment of $637,000. Lytle's conspirators were sentenced to 24 months and 15 months, respectively.[34][35]
Evidence does not support a benefit in
delayed-onset muscle soreness.[40] It may be useful for muscle pain and injuries.[41]
A 2008
Cochrane Library review concluded that LLLT has insufficient evidence for treatment of nonspecific
low back pain,[42] a finding echoed in a 2010 review of chronic low back pain.[43] A 2015 review found benefit in nonspecific chronic low-back pain.[15] LLLT may be useful in the treatment of both acute and chronic
neck pain.[16] In 2013, however, a systematic review and
meta-analysis of LLLT for neck pain indicated that the benefit was not of significant importance and that the evidence had a high risk of bias.[44] In a study testing the efficacy of low-level laser therapy treating plantar fasciitis found that LLLT significantly reduces pain in lower extremity tendinopathy and plantar fasciitis in the short and medium terms. [45] The same study also stated that while comparing the effect of LLLT to that of therapeutic ultrasound in persons with patellar tendinopathy, and they found a statistically significant effect in favour of LLLT, both on pain reduction and function.[46]
There are tentative data that LLLT is useful in the short-term treatment of
pain caused by
rheumatoid arthritis,[7] and possibly chronic joint disorders.[10] Research that compared the effects of LLLT against other treatments, sham treatments, or no treatment at all, and randomized adult patients with rheumatoid arthritis to receive it were considered. These outcomes included pain, functional capacity, adverse events, inflammation, disease activity, range of motion, stiffness in the morning, muscle strength, and quality of life.[47] The findings indicate that the differences between utilizing a sham and an infrared laser may be negligible or nonexistent in terms of pain, stiffness in the morning, grip strength, functional ability, inflammation, range of motion, disease activity, and side events. We also discovered that the data about the effects of laser acupuncture against reflexology in terms of functional ability, quality of life, and inflammation is quite hazy, and about the effects of red laser versus sham in terms of pain, morning stiffness, and side events.[48] The usefulness of red laser, laser acupuncture, and reflexology in the treatment of RA patients is not well enough demonstrated. [49] A 2019 systematic review and meta-analysis found evidence for pain reduction in
osteoarthritis.[14] While it does not appear to improve pain in temporomandibular disorders, it may improve function.[50]
Similarly, the use of lasers to treat
chronic periodontitis[18] and to speed healing of
infections around dental implants[19] is suggested, but there is insufficient evidence to indicate a use superior to traditional practices.[53] There is tentative evidence for dentin hypersensitivity.[54] It does not appear to be useful for orthodontic pain[55][56] LLLT might be useful for wisdom tooth extraction (complications).[57]
Hair loss
LLLT has been studied as a treatment for
hair loss; a review in 2012 found little evidence to support the use of lasers to treat hair loss.[58] A 2014 review found tentative evidence for benefit for lasers,[59] while another 2014 review concluded that the results were mixed, had a high risk of bias, and that its effectiveness was unclear.[60] A 2015 review found tentative evidence of benefit.[61] Additionally, a 2017 review of clinical trials found 10 of 11 trials reviewed "demonstrated significant improvement of androgenic alopecia in comparison to baseline or controls when treated with LLLT."[62]
LLLT is shown to increase hair density and growth in both genders. The types of devices (hat, comb, helmet) and duration did not alter the effectiveness,[63] with more emphasis to be placed on lasers compared to LEDs.[64] Ultraviolet and infrared light are more effective for alopecia areata, while red light and infrared light is more effective for androgenetic alopecia.[65]
Medical reviews suggest that LLLT is as effective or potentially more than other non invasive and traditional therapies like minoxidil and finasteride but further studies such as RCTs, long term follow up studies, and larger double blinded trials need to be conducted to confirm the initial findings.[66][67][68]
Brain injuries
LLLT has been studied for
traumatic brain injury (TBI) and
stroke among other conditions.[11] When applied to the head it is known as transcranial photobiomodulation or transcranial low level light therapy.
Cancer treatment side effects
LLLT has been studied as a way to reduce pain and swelling in breast-cancer related
lymphedema.[69][20] The 2015 systematic review & meta-analysis by Smoot, Chiavola-Larson, et al found:
“Moderate-strength evidence supports LLLT in the management of [breast cancer related lymphoedema], with […] reductions in volume and pain immediately after conclusion of LLLT treatments. Greater reductions in volume [of lymph nodes or surrounding tissues] were found with the use of LLLT than in treatments without it.”[70]
Stem cells
An ongoing area of research is the application of LLLT for increasing cell proliferation, including
stem cells.[71]
Wound healing
Low level laser therapy has been studied as a potential treatment for
chronic wounds, and higher-power lasers have sometimes been successfully used to close acute wounds as an alternative to
stitching.[72] However, as of 2012[update] and due to inconsistent results and the low quality of extant research, reviews in the scientific literature have not supported its widespread application.[72][73]
^
abChow R, Johnson M, Lopes-Martins R, Bjordal J (Nov 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". Lancet. 374 (9705): 1897–1908.
doi:
10.1016/S0140-6736(09)61522-1.
PMID19913903.
S2CID16336402.
^
abTumilty S., Munn J., McDonough S., Hurley DA, Basford JR, Baxter GD (2010). "Low Level Laser Treatment of Tendinopathy: A Systematic Review with Meta-analysis". Photomedicine and Laser Surgery. 28 (1): 3–16.
doi:
10.1089/pho.2008.2470.
PMID19708800.
S2CID10634480.
^
abSculean A, Schwarz F, Becker J (2005). "Anti-infective therapy with an Er:YAG laser: influence on peri-implant healing". Expert Review of Medical Devices. 2 (3): 267–76.
doi:
10.1586/17434440.2.3.267.
PMID16288590.
S2CID5544626.
^
abDa Silva JP, Da Silva MA, Almeida AP, Junior IL, Matos AP (2010). "Laser Therapy in the Tissue Repair Process: A Literature Review". Photomedicine and Laser Surgery. 28 (1): 17–21.
doi:
10.1089/pho.2008.2372.
PMID19764898.
^Blue Cross and Blue Shield of Kansas City (Blue KC).
"Low-Level Laser Therapy"(PDF). Policy No. 2.01.56. Retrieved 2 February 2019. (Policy reviewed each June; if link is dead try replacing "06-18" with a more recent year.)
^Nampo FK, Cavalheri V, Ramos Sd, Camargo EA (2016-01-01). "Effect of low-level phototherapy on delayed onset muscle soreness: a systematic review and meta-analysis". Lasers in Medical Science. 31 (1): 165–177.
doi:
10.1007/s10103-015-1832-4.
ISSN1435-604X.
PMID26563953.
S2CID21912028.
^Kadhim-Saleh A, Maganti H, Ghert M, Singh S, Farrokhyar F (2013-10-01). "Is low-level laser therapy in relieving neck pain effective? Systematic review and meta-analysis". Rheumatology International. 33 (10): 2493–2501.
doi:
10.1007/s00296-013-2742-z.
ISSN1437-160X.
PMID23579335.
S2CID7057247. his systematic review provides inconclusive evidence because of significant between-study heterogeneity and potential risk of bias.
^Chen J, Huang Z, Ge M, Gao M (2015-04-01). "Efficacy of low-level laser therapy in the treatment of TMDs: a meta-analysis of 14 randomised controlled trials". Journal of Oral Rehabilitation. 42 (4): 291–299.
doi:
10.1111/joor.12258.
ISSN1365-2842.
PMID25491183.
^Haslerud S, Magnussen LH, Joensen J, Lopes-Martins RA, Bjordal JM (2015-06-01). "The efficacy of low-level laser therapy for shoulder tendinopathy: a systematic review and meta-analysis of randomized controlled trials". Physiotherapy Research International. 20 (2): 108–125.
doi:
10.1002/pri.1606.
hdl:1956/17899.
ISSN1471-2865.
PMID25450903.
^Eslamian L, Borzabadi-Farahani A, Hassanzadeh-Azhiri A, Badiee M, Fekrazad R (2013-01-20). "The effect of 810-nm low-level laser therapy on pain caused by orthodontic elastomeric separators". Lasers in Medical Science. 29 (2): 559–564.
doi:
10.1007/s10103-012-1258-1.
PMID23334785.
S2CID25416518.
^He WL, Yu FY, Li CJ, Pan J, Zhuang R, Duan PJ (2015-08-01). "A systematic review and meta-analysis on the efficacy of low-level laser therapy in the management of complication after mandibular third molar surgery". Lasers in Medical Science. 30 (6): 1779–1788.
doi:
10.1007/s10103-014-1634-0.
ISSN1435-604X.
PMID25098769.
S2CID22627779.
^Rangwala S, Rashid RM (Feb 2012). "Alopecia: a review of laser and light therapies". Dermatology Online Journal. 18 (2): 3.
doi:
10.5070/D31JT041T2.
ISSN1087-2108.
PMID22398224. Since then, a number of studies have suggested the use of lasers as an effective way to treat alopecia, particularly androgenetic alopecia and alopecia areata, but there is still a paucity of independent, peer-reviewed blinded clinical trials.
^Gupta AK, Daigle D (April 2014). "The use of low-level light therapy in the treatment of androgenetic alopecia and female pattern hair loss". The Journal of Dermatological Treatment. 25 (2): 162–3.
doi:
10.3109/09546634.2013.832134.
PMID23924031.
S2CID13565213.
^Zarei M, Wikramanayake TC, Falto-Aizpurua L, Schachner LA, Jimenez JJ (2015-12-21). "Low level laser therapy and hair regrowth: an evidence-based review". Lasers in Medical Science. 31 (2): 363–71.
doi:
10.1007/s10103-015-1818-2.
ISSN1435-604X.
PMID26690359.
S2CID22028662.
^Darwin E, Heyes A, Hirt PA, Wikramanayake T, Jimenez JJ (2018). "Low-level laser therapy for the treatment of androgenic alopecia: a review". Lasers in Medical Science. 33 (2): 425–434.
doi:
10.1007/s10103-017-2385-5.
PMID29270707.
S2CID23783876.
^Liu KH, Liu D, Chen YT, Chin SY (2019-01-31). "Comparative effectiveness of low-level laser therapy for adult androgenic alopecia: a system review and meta-analysis of randomized controlled trials". Lasers in Medical Science. 34 (6). Springer Science and Business Media LLC: 1063–1069.
doi:
10.1007/s10103-019-02723-6.
ISSN0268-8921.
PMID30706177.
S2CID59524423.
^Zhang Y, Su J, Ma K, Fu X, Zhang C (2022-04-25). "Photobiomodulation Therapy With Different Wavebands for Hair Loss: A Systematic Review and Meta-Analysis". Dermatologic Surgery. 48 (7). Ovid Technologies (Wolters Kluwer Health): 737–740.
doi:
10.1097/dss.0000000000003472.
ISSN1076-0512.
PMID35510860.
S2CID248526019.
^Darwin E, Heyes A, Hirt PA, Wikramanayake TC, Jimenez JJ (2017-12-21). "Low-level laser therapy for the treatment of androgenic alopecia: a review". Lasers in Medical Science. 33 (2). Springer Science and Business Media LLC: 425–434.
doi:
10.1007/s10103-017-2385-5.
ISSN0268-8921.
PMID29270707.
S2CID23783876.
^Smoot B, Chiavola-Larson L, Lee J, Manibusan H, Allen DD (2015-06-01). "Effect of low-level laser therapy on pain and swelling in women with breast cancer-related lymphedema: a systematic review and meta-analysis". Journal of Cancer Survivorship: Research and Practice. 9 (2): 287–304.
doi:
10.1007/s11764-014-0411-1.
ISSN1932-2267.
PMID25432632.
S2CID27555240.
^Borzabadi-Farahani A (2016-07-22). "Effect of low-level laser irradiation on proliferation of human dental mesenchymal stem cells; a systemic review". Journal of Photochemistry and Photobiology B: Biology. 162: 577–582.
doi:
10.1016/j.jphotobiol.2016.07.022.
PMID27475781.
^
abBouzari N, Elsaie ML, Nouri K (2012). "Laser and Light for Wound Healing Stimulation". In Nouri K (ed.). Lasers in Dermatology and Medicine. Springer London. pp. 267–275.
doi:
10.1007/978-0-85729-281-0_20.
ISBN978-0-85729-281-0.