Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
. 2012 Feb;40(2):516-33.
doi: 10.1007/s10439-011-0454-7. Epub 2011 Nov 2.

The nuts and bolts of low-level laser (light) therapy

Hoon Chung  1 , Tianhong Dai, Sulbha K Sharma, Ying-Ying Huang, James D Carroll, Michael R Hamblin
Affiliations
Review

The nuts and bolts of low-level laser (light) therapy

Hoon Chung et al. Ann Biomed Eng. 2012 Feb.

Abstract

Soon after the discovery of lasers in the 1960s it was realized that laser therapy had the potential to improve wound healing and reduce pain, inflammation and swelling. In recent years the field sometimes known as photobiomodulation has broadened to include light-emitting diodes and other light sources, and the range of wavelengths used now includes many in the red and near infrared. The term "low level laser therapy" or LLLT has become widely recognized and implies the existence of the biphasic dose response or the Arndt-Schulz curve. This review will cover the mechanisms of action of LLLT at a cellular and at a tissular level and will summarize the various light sources and principles of dosimetry that are employed in clinical practice. The range of diseases, injuries, and conditions that can be benefited by LLLT will be summarized with an emphasis on those that have reported randomized controlled clinical trials. Serious life-threatening diseases such as stroke, heart attack, spinal cord injury, and traumatic brain injury may soon be amenable to LLLT therapy.

PubMed Disclaimer

Conflict of interest statement

CONFLICTS OF INTEREST James D. Carroll is the owner of THOR Photomedicine, a company which sells LLLT devices.

Figures

FIGURE 1
FIGURE 1
Basic physics of LLLT. (a) Light as an electromagnetic wave. (b) Gaussian laser beam profile. (c) Snellius’ law of reflection. (d) Optical window because of minimized absorption and scattering of light by the most important tissue chromophores in the near-infrared spectral region.
FIGURE 2
FIGURE 2
Cellular mechanisms of LLLT. Schematic diagram showing the absorption of red or near infrared (NIR) light by specific cellular chromophores or photoacceptors localized in the mitochondrial. During this process in mitochondria respiration chain ATP production will increase, and reactive oxygen species (ROS) are generated; nitric oxide is released or generated. These cytosolic responses may in turn induce transcriptional changes via activation of transcription factors (e.g., NF-κB and AP1).
FIGURE 3
FIGURE 3
Two possible sources of nitric oxide (NO) release from cytochrome c oxidase (CCO). Path1 shows CCO can act as a nitrite reductase enzyme: Path 2 shows possible photo-dissociation of NO from CCO.
FIGURE 4
FIGURE 4
Biphasic dose response in LLLT. Three dimensional plot illustrating effects of varying irradiation time equivalent to fluence or irradiance on the biological response resulting in stimulation or inhibition.
FIGURE 5
FIGURE 5
Some examples of LLLT devices and applications. (a and b) Intravascular laser therapy (Institute of Biological Laser therapy, Gottingen, Germany). (c and d) Laserneedle acupuncture system (Laserneedle GmbH, Glienicke-Nordbahn, Germany). (e and f) Lasercomb (Lexington Int LLC, Boca Raton, FL) for hair regrowth. (g) Laser cap (Transdermal Cap Inc, Gates Mills, OH) for hair regrowth.
See this image and copyright information in PMC

References

    1. Abergel RP, Lyons RF, Castel JC, Dwyer RM, Uitto J. Biostimulation of wound healing by lasers: experimental approaches in animal models and in fibroblast cultures. J Dermatol Surg Oncol. 1987;13:127–133. - PubMed
    1. Ad N, Oron U. Impact of low level laser irradiation on infarct size in the rat following myocardial infarction. Int J Cardiol. 2001;80:109–116. - PubMed
    1. Almeida-Lopes L, Rigau J, Zangaro RA. Comparison of the low level laser therapy effects on cultured human gingival fibroblasts proliferation using different irradiance and same fluence. Lasers Surg Med. 2001;29:179–184. - PubMed
    1. Anneroth G, Hall G, Ryden H, Zetterqvist L. The effect of low-energy infra-red laser radiation on wound healing in rats. Br J Oral Maxillofac Surg. 1988;26:12–17. - PubMed
    1. Antunes F, Boveris A, Cadenas E. On the mechanism and biology of cytochrome oxidase inhibition by nitric oxide. Proc Natl Acad Sci USA. 2004;101:16774–16779. - PMC - PubMed

Publication types

LinkOut - more resources