Low-level laser therapy (LLLT), cold laser therapy or photobiomodulation (PBM) is a medical treatment approach that applies low-level (low- power)

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...

s or light-emitting diodes (LEDs) to the surface of the body. Whereas high-power lasers are used in

laser medicine Laser medicine is the use of lasers in medical diagnosis, treatments, or therapies, such as laser photodynamic therapy, photorejuvenation, and laser surgery. The word ''laser'' stands for "light amplification by stimulated emission of radiat ...

to cut or destroy tissue, it is claimed that application of low-power lasers stimulates healing, relieves pain, and enhances cell function. Described sometimes as Low-level Red-light Therapy (LLRL), has effects that appear to be limited to a specified set of wavelengths. The effectiveness of red light therapy for treating various conditions is still under investigation. Repeated low level red light therapy may be effective for controlling

myopia Myopia, also known as near-sightedness and short-sightedness, is an eye condition where light from distant objects focuses in front of, instead of on, the retina. As a result, distant objects appear blurry, while close objects appear normal. ...

in children. Several such devices are cleared by the

United States Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...

(FDA), and low level red light therapy is being tested for treating a range of medical problems including

rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects synovial joint, joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and h ...

and oral mucositis.

Mechanism

Research is ongoing about the mechanism of LLLT. The effects of LLLT appear to be limited to a specified set of wavelengths of laser, and administering LLLT below the dose range does not appear to be effective.

Photochemical reactions Organic photochemistry encompasses organic reactions that are induced by the action of light. The absorption of ultraviolet light by organic molecules often leads to reactions. In the earliest days, sunlight was employed, while in more modern times ...

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 The enzyme cytochrome c oxidase or Complex IV (was , now reclassified as a translocasEC 7.1.1.9 is a large transmembrane protein complex found in bacteria, archaea, and the mitochondria of eukaryotes. It is the last enzyme in the Cellular respir ...

which is involved in the

electron transport chain An electron transport chain (ETC) is a series of protein complexes and other molecules which transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples th ...

mitochondria A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...

, which is the generally accepted theory.

Medical uses

Various LLLT devices have been promoted for use in treatment of several musculoskeletal conditions including

carpal tunnel syndrome Carpal tunnel syndrome (CTS) is a nerve compression syndrome associated with the collected signs and symptoms of Pathophysiology of nerve entrapment#Compression, compression of the median nerve at the carpal tunnel in the wrist. Carpal tunn ...

(CTS),

fibromyalgia Fibromyalgia (FM) is a functional somatic syndrome with symptoms of widespread chronic pain, accompanied by fatigue, sleep disturbance including awakening unrefreshed, and Cognitive deficit, cognitive symptoms. Other symptoms can include he ...

osteoarthritis Osteoarthritis is a type of degenerative joint disease that results from breakdown of articular cartilage, joint cartilage and underlying bone. A form of arthritis, it is believed to be the fourth leading cause of disability in the world, affect ...

, and

. They have also been promoted for

temporomandibular joint In anatomy, the temporomandibular joints (TMJ) are the two joints connecting the jawbone to the skull. It is a bilateral Synovial joint, synovial articulation between the temporal bone of the skull above and the condylar process of mandible be ...

disorders,

wound healing Wound healing refers to a living organism's replacement of destroyed or damaged tissue by newly produced tissue. In undamaged skin, the epidermis (surface, epithelial layer) and dermis (deeper, connective layer) form a protective barrier again ...

smoking cessation Smoking cessation, usually called quitting smoking or stopping smoking, is the process of discontinuing tobacco smoking. Tobacco smoke contains nicotine, which is Addiction, addictive and can cause Substance dependence, dependence. As a resu ...

, and

tuberculosis Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is a contagious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can al ...

. LLLT appears to be effective for preventing oral mucositis in recipients of a

stem cell transplant Hematopoietic stem-cell transplantation (HSCT) is the transplantation of multipotent hematopoietic stem cells, usually derived from bone marrow, peripheral blood, or umbilical cord blood, in order to replicate inside a patient and produce a ...

with chemotherapy. In other areas, evidence for LLLT remains conflicted. Some studies suggest that LLLT may be modestly effective in relieving short-term pain for

, chronic

low back pain Low back pain or wiktionary:lumbago#Etymology, lumbago is a common musculoskeletal disorders, disorder involving the muscles, nerves, and bones of the back, in between the lower edge of the ribs and the lower fold of the buttocks. Pain can var ...

, acute and chronic

neck pain The neck is the part of the body in many vertebrates that connects the head to the torso. It supports the weight of the head and protects the nerves that transmit sensory and motor information between the brain and the rest of the body. Addition ...

tendinopathy Tendinopathy is a type of tendon disorder that results in pain, swelling, and impaired function. The pain is typically worse with movement. It most commonly occurs around the shoulder ( rotator cuff tendinitis, biceps tendinitis), elbow ( tenn ...

, and chronic joint disorders. The evidence for LLLT being useful in dentistry, and in the treatment of

is unclear. Concerns have been raised in the literature about brain stimulation techniques that rely upon low-level (low-power) lasers and light-emitting diodes (LEDs). The transcranial photobiomodulation or transcranial low level light therapy is limited in neuromodulation due to several reasons: * An excessive dose of radiation can be harmful.Smith K.C. (2005). Laser (and LED) therapy is phototherapy. Photomed. Laser Surg. 23, 78–80. Therefore, at adequate doses of light there may be stimulation of growth, but at high doses excessive singlet oxygen may be produced and its chemical action may be harmful to cells. * Regarding LED light therapy, this neurostimulation method based on the light-emitting diodes stimulation cannot pass through the skin, only laser can penetrate deeper tissues and stimulate brain areas accordingly. The penetration depth of white light and LED light into the skin increases with increasing wavelength from the UV to the visible light range, and then decreases again in the IR range depending on the selected optical properties. This depth further increases if the thickness of the stratum corneum decreases. Broadband polychromatic light (white light) and LED radiation can only penetrate 0.0017 mm to 5 mm of tissue. For example, research shows that at wavelengths of 450 nm and 650 nm only 1% of the light reaches approximately 1.6 mm and very little reaches 5 mm. Only laser radiation can propagate into deeper tissues. * Since the action spectrum for tissue regeneration and repair consist of more than one wavelength, laser and LED light sources may offer some disadvantages, destroying healthy cells. We still lack knowledge of mental processes at the cellular level. The link between neuronal activity and mental processes is still an intriguing research question and a problem in treatment targeting. Therefore, no one can be sure whether the laser beam only reaches the neuronal structures in the brain that need treatment. An undetermined dose of radiation and the target of radiation can destroy healthy cells during the treatment procedure. There is not enough information from clinical trials to compare the effectiveness of different types of devices or device parameters (wavelengths, power output, session time, area of actuation).

Veterinary use

Veterinary clinics use cold laser devices to treat a wide variety of ailments, from arthritis to wounds, on dogs and cats. 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". 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.

Contraindications

Based on the results of a systematic review, there is no evidence to suggest that people with cancer or people who are at risk of getting cancer should avoid photobiomodulation.

Side effects

There are some reports of mild pain or skin irritation after red light therapy. The long term effects on the skin or on the hair are not known. Eye protection is suggested for some devices. For skin applications, different wavelengths of light may result in different 'biological effects' depending on the person's skin type, race, and ethnicity. Clinical guideline suggest that a dermatologist is consulted before undergoing treatment. For safety, if a person chooses to use red light therapy, a device that has been approved for use on humans by the country the person lives in is recommended. For example, in the US, it is suggested to only use devices approved by the

FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

for dermatologic application.

Society and culture

History

Faroese

physician A physician, medical practitioner (British English), medical doctor, or simply doctor is a health professional who practices medicine, which is concerned with promoting, maintaining or restoring health through the Medical education, study, Med ...

Niels Finsen is believed to be the father of modern

light therapy Light therapy, also called phototherapy or bright light therapy is the exposure to direct sunlight or artificial light at controlled wavelengths in order to treat a variety of medical disorders, including seasonal affective disorder (SAD), circ ...

. He used red light to treat

smallpox Smallpox was an infectious disease caused by Variola virus (often called Smallpox virus), which belongs to the genus '' Orthopoxvirus''. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (W ...

lesions. He received the

Nobel Prize in Physiology or Medicine The Nobel Prize in Physiology or Medicine () is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, acco ...

in 1903.

Scientific evidence Scientific evidence is evidence that serves to either support or counter a scientific theory or hypothesis, although scientists also use evidence in other ways, such as when applying theories to practical problems. "Discussions about empirical ev ...

for some of his treatments is lacking, and later eradication of smallpox and development of

antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

for

rendered light therapy obsolete for these diseases. Hungarian physician and surgeon Endre Mester (1903–1984) is credited with the discovery of the biological effects of low power lasers, which occurred a few years after the 1960 invention of the

ruby laser A ruby laser is a solid-state laser that uses a synthetic ruby crystal as its gain medium. The first working laser was a ruby laser made by Theodore H. "Ted" Maiman at Hughes Research Laboratories on May 16, 1960. Ruby lasers produce pulses of ...

and the 1961 invention of the helium–neon (HeNe) laser. 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 was not 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. He published those results in 1967. He went on to show that low level HeNe light could accelerate wound healing in mice. By the 1970s, he was applying low level laser light to treat people with skin ulcers. In 1974, he founded the Laser Research Center at the Semmelweis Medical University in

Budapest Budapest is the Capital city, capital and List of cities and towns of Hungary, most populous city of Hungary. It is the List of cities in the European Union by population within city limits, tenth-largest city in the European Union by popul ...

, and continued working there for the remainder of his life. His sons carried on his work and brought it to the United States. 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. 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 A light-emitting diode (LED) is a semiconductor device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of pho ...

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.

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.. However LLLT has been marketed and researched under a number of other terms, including red light therapy, 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.American Cancer Society
Cold Laser Therapy
Page archived April 24, 2015 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), 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. 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.

Reimbursement

Blue Cross Blue Shield Association Blue Cross Blue Shield Association, also known as BCBS, BCBSA, or The Blues, is a United States–based federation with 33 independent and locally operated BCBSA companies that provide health insurance to more than 115 million people in the U ...

and

Aetna Aetna Inc. ( ) is an American managed health care company that sells traditional and consumer directed health care insurance and related services, such as medical, pharmaceutical, dental, behavioral health, long-term care, and disability plans, ...

provide coverage for the prevention of oral mucositis, but not any other reason."Infrared therapy"
Aetna clinical policy bulletin 0363, reviewed June 17, 2020. Aetna has additional information in it

The

Centers for Medicare and Medicaid Services The Centers for Medicare & Medicaid Services (CMS) is a federal agency within the United States Department of Health and Human Services (HHS) that administers the Medicare program and works in partnership with state governments to administer ...

does not provide coverage for LLLT.

&" target="_blank" class="mw-redirect" title=""Decision memo for infrared therapy devices" (CAG00291N)">"Decision memo for infrared therapy devices" (CAG00291N)
Center for Medicare & Medicaid Services, Oct 24, 2006.

Cigna The Cigna Group is an American multinational for-profit managed healthcare and insurance company based in Bloomfield, Connecticut. Its insurance subsidiaries are major providers of medical, dental, disability, life and accident insurance and r ...

lists LLLT as "experimental, investigational, or unproven for any indication" and provides literature review summaries for a number of conditions.

Research

Musculoskeletal

Evidence does not support a benefit in delayed-onset muscle soreness. It may be useful for muscle pain and injuries. A 2008

Cochrane Library The Cochrane Library (named after Archie Cochrane) is a collection of databases in medicine and other healthcare specialties provided by Cochrane and other organizations. At its core is the collection of Cochrane Reviews, a database of systema ...

review concluded that LLLT has insufficient evidence for treatment of nonspecific

, a finding echoed in a 2010 review of chronic low back pain. A 2015 review found benefit in nonspecific chronic low-back pain. LLLT may be useful in the treatment of both acute and chronic

. In 2013, however, a systematic review and

meta-analysis Meta-analysis is a method of synthesis of quantitative data from multiple independent studies addressing a common research question. An important part of this method involves computing a combined effect size across all of the studies. As such, th ...

of LLLT for neck pain indicated that the benefit was not of significant importance and that the evidence had a high risk of bias. 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. 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. There are tentative data that LLLT is useful in the short-term treatment of

pain Pain is a distressing feeling often caused by intense or damaging Stimulus (physiology), stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sense, sensory and emotional experience associated with, or res ...

caused by

, and possibly chronic joint disorders. 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. 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. It was 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. The usefulness of red laser, laser acupuncture, and reflexology in the treatment of RA patients is not well enough demonstrated. A 2019 systematic review and meta-analysis found evidence for pain reduction in

. While it does not appear to improve pain in temporomandibular disorders, it may improve function. There is tentative evidence of benefit in

. A 2014 review found benefit in shoulder tendinopathy. A 2014

Cochrane review Cochrane is a British international charitable organisation formed to synthesize medical research findings to facilitate evidence-based choices about health interventions involving health professionals, patients and policy makers. It includes ...

found tentative evidence that it may help in

frozen shoulder Adhesive capsulitis, also known as frozen shoulder, is a condition associated with shoulder pain and stiffness. It is a common shoulder ailment that is marked by pain and a loss of range of motion, particularly in external rotation. There is ...

Mouth

Similarly, the use of lasers to treat chronic periodontitis and to speed healing of infections around dental implants is suggested, but there is insufficient evidence to indicate a use superior to traditional practices. There is tentative evidence for dentin hypersensitivity. It does not appear to be useful for orthodontic pain LLLT might be useful for wisdom tooth extraction (complications).

Hair loss

LLLT has been studied as a treatment for

hair loss Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scarring ...

; a review in 2012 found little evidence to support the use of lasers to treat hair loss. A 2014 review found tentative evidence for benefit for lasers, while another 2014 review concluded that the results were mixed, had a high risk of bias, and that its effectiveness was unclear. A 2015 review found tentative evidence of benefit. 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." 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, with more emphasis to be placed on lasers compared to LEDs. Ultraviolet and infrared light are more effective for alopecia areata, while red light and infrared light is more effective for androgenetic alopecia. Medical reviews suggest that LLLT is as effective or potentially more than other non invasive and traditional therapies such as

minoxidil Minoxidil is a medication used for the treatment of high blood pressure and pattern hair loss. It is an antihypertensive and a vasodilator. It is available as a generic medication by prescription in oral administration, oral tablet (pharmacy), ...

and

finasteride Finasteride, sold under the brand names Proscar and Propecia among others, is a medication used to treat pattern hair loss and benign prostatic hyperplasia (BPH) in men. It can also be used to treat hirsutism, excessive hair growth in women. It ...

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.

Brain injuries

LLLT has been studied for

traumatic brain injury A traumatic brain injury (TBI), also known as an intracranial injury, is an injury to the brain caused by an external force. TBI can be classified based on severity ranging from mild traumatic brain injury (mTBI/concussion) to severe traumati ...

(TBI) and

stroke Stroke is a medical condition in which poor cerebral circulation, blood flow to a part of the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemor ...

among other conditions. 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 Lymphedema, also known as lymphoedema and lymphatic edema, is a condition of localized edema, swelling caused by a compromised lymphatic system. The lymphatic system functions as a critical portion of the body's immune system and returns inters ...

. The 2015 systematic review & meta-analysis by Smoot, Chiavola-Larson, et al found “Moderate-strength evidence supports LLLT in the management of reast cancer related lymphoedema with ��reductions in volume and pain immediately after conclusion of LLLT treatments. Greater reductions in volume f lymph nodes or surrounding tissueswere found with the use of LLLT than in treatments without it.”

Stem cells

An ongoing area of research is the application of LLLT for increasing cell proliferation, including

stem cells In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell ...

Wound healing

Low level laser therapy has been studied as a potential treatment for

chronic wound A chronic wound is a wound A wound is any disruption of or damage to living tissue, such as skin, mucous membranes, or organs. Wounds can either be the sudden result of direct trauma (mechanical, thermal, chemical), or can develop slowly over t ...

s, and higher-power lasers have sometimes been successfully used to close acute wounds as an alternative to stitching. However, and due to inconsistent results and the low quality of extant research, reviews in the scientific literature have not supported its widespread application.

References

{{Lasers Laser medicine Alternative medicine Bioelectromagnetic-based therapies Light therapy Hungarian inventions