Low Level Laser Therapy/Photobiomodulation (PBM) is the term used to describe the mechanistic/scientific basis for this photonic specialty and photobiomodulation therapy (PBMT) as the term for its therapeutic application. PBMT was first developed in the 1960s. During the early years, this emerging photonic application was plagued by a number of problems including inconsistent terminology. A number of terms were introduced such as Biostimulation, Cold/Cool Laser, Low Level laser therapy, Soft Laser and Low Power Laser Therapy. Based on recent consensus in the field, PBM and PBMT are now considered the terms of choice.  In 2015 thanks to the efforts of Dr. Praveen Arany, PBMT was added to the National Library of Medicine MeSH database as an entry term to the existing record of laser therapy, low-level. In summary, PBM and PBMT are accurate and specific terms for this effective and important therapeutic application of light. 
In this therapy, a light source is placed near or in contact with the skin, allowing the light energy (photons) to penetrate tissue where it interacts with chromophores located in cells resulting in photo-physical and photochemical changes that lead to alterations at the molecular, cellular and tissue levels of the body. Light induces a complex chain of physiological reactions in diseased and damaged tissues to accelerate wound healing and tissue regeneration, increase circulation, reduce acute inflammation, reduce acute and chronic pain and help restore normal cellular function. Interestingly, recent research indicates that light can enhance performance in normal tissues and cells. Thus, Laser and LED beams of light can stimulate the cells in the body that repair tissue, reduce inflammation and transmit pain.

Light can stimulate or inhibit cellular function according to its intensity and the time applied. Lasers and LED's produce intense beams of light at specific wavelengths. When the right wavelength at the right intensity is used at the correct anatomical location for the right amount of time you can stimulate repair, resolve inflammation and reduce pain.
In addition, high intensity single point lasers can release trigger points and treat acupuncture points instead of needles.
The use of low levels of visible or near-infrared (NIR) light for reducing pain, inflammation and edema, promoting healing of wounds, deeper tissues and nerves, and preventing tissue damage has been known for almost forty years since the invention of lasers. Originally thought to be a peculiar property of laser light (soft or cold lasers), the subject has now broadened to include photo-biomodulation and photo-biostimulation using non-coherent light.

Low-level laser therapy (LLLT) has only been used in the United States since 2002, although it has been used widely in Europe and Asia for the past several decades. There is substantial clinical evidence published in peer reviewed medical journals that "cold" Low Level laser (LLLT) Acupuncture therapy can stimulate repair of tissue, reduce inflammation and relieve pain in musculoskeletal disorders.
There are numerous examples of light induced photochemical reactions in biological systems. Our vision is based upon light interacting with photosensitive cells in our retinas called photoreceptors. When light is absorbed by these cells, a photochemical reaction occurs converting light energy into electrical signals that are transmitted to the visual processing centers of the brain. Vitamin D synthesis in our skin is another example of a photochemical reaction. When the ultraviolet B (UVB) wavelength in sunlight strikes our skin, it converts a universally present form of cholesterol, 7-dehydrocholesterol to vitamin D3.  The negative effects of the absence of light on the human body are also well known. Two examples include seasonal affective disorder (SAD) and lack of vitamin D production leading to rickets.

• Nerve Regeneration
• Tissue Regeneration
• Increase in White/Gray Matter
• Improvement in overall Neuro-Plasticity
• Soft Tissue Injuries
• Joint conditions
• Back and Neck Pain
• Spinal Cord Injury
• Brian Injury
• Trauma paralysis in stroke paralysis in head injury multiple sclerosis
• Pseudo Bulbar Palsy
• Cerebral palsy in babies / children spinal cord injury
• Peripheral Facial Paralysis (Bell's palsy) 
• Other applications such as shingles, post-operative pain, also respond well.

It is purely free from side effects and lots of trials and research supported this fact and this is the reason that FDI (US) has approved its use.