The Evolution and Mechanisms of Photobiomodulation (PBM) Therapy

What is Photobiomodulation Therapy (PBM)?

Photobiomodulation Therapy (PBM) is a form of light therapy that utilizes non-ionizing light sources within the visible (400-700 nm) and near-infrared (700-1100 nm) electromagnetic spectrum, including lasers. This therapy is widely used for its anti-inflammatory properties, collagen production stimulation, improved blood circulation, pain relief, mood enhancement, melatonin production stimulation, and sleep quality improvement.

PBM is a non-thermal process where endogenous chromophores trigger photophysical and photochemical reactions at various physiological levels. These processes lead to beneficial therapeutic outcomes, such as pain and inflammation reduction, immune modulation, and tissue regeneration.

PBM is also used preventively to avoid diseases, enhance brain health and cognitive function, promote overall well-being, and improve athletic performance. While photobiomodulation naturally occurs under sunlight, PBM therapy employs artificial light sources with selected beneficial wavelengths applied directly to affected organs and tissues. Unlike sunlight, which contains a mix of beneficial, neutral, and harmful wavelengths (such as shortwave UV), PBM ensures only safe and effective wavelengths are used in targeted treatments.

The Evolution of the Term “Photobiomodulation”

Terms such as “Cold Laser” and “Low-Level Laser Therapy (LLLT)” have traditionally been used to describe the process of using low-intensity light to achieve therapeutic effects without heat-induced tissue damage. However, these terms often caused confusion as they did not clearly distinguish PBM from other heat-based laser therapies.

In September 2014, the North American Association for Light Therapy (NAALT) and the World Association for Laser Therapy (WALT) agreed to adopt “Photobiomodulation Therapy” as the preferred term. This designation was officially included in the Medical Subject Headings (MeSH) database in November 2015.

Historical Development of Photobiomodulation Therapy

The therapeutic use of light dates back to approximately 1550 BCE, as recorded in ancient Egyptian papyrus texts. Early physicians observed that sunlight, particularly specific colors (a practice known as chromotherapy), could aid in healing.

Ancient civilizations in the Indus Valley (India) and pre-imperial China also explored light-based treatments for health. In Greece, scientists studied the medical benefits of sunlight, referring to it as heliotherapy (from the god Helios, meaning “sun”). The Romans commercialized heliotherapy into “solariums,” which gained widespread popularity throughout Europe as the Roman Empire expanded.

By the 19th century, doctors and scientists began studying the biomedical mechanisms of light therapy. In 1903, Dr. Niels Ryberg Finsen won the Nobel Prize in Medicine for successfully treating lupus vulgaris using light from gas lamps and arc lamps, bringing international recognition to light therapy.

During the 1960s, with the advent of laser technology, scientists debated whether low-power lasers (which did not cause burns) could induce cancer. Dr. Endre Mester at Semmelweis University in Budapest conducted systematic studies that led to an unexpected discovery: not only did low-level laser irradiation fail to cause cancer, but it also accelerated hair regrowth in shaved mice.

By 1971, research confirmed that lasers could stimulate hair growth and accelerate wound healing. However, early lasers in the 1960s and 70s were large, fragile devices composed of gas-filled glass tubes and delicate optical lenses, requiring heavy power sources.

The Introduction of LEDs in PBM

In 1996, with support from NASA’s Space Shuttle Program, Dr. Harry T. Whelan at the University of Wisconsin introduced LEDs as an alternative to lasers in PBM therapy. By 1999, he demonstrated that LEDs were just as effective as lasers in accelerating wound healing. In 2003, his pioneering research on PBM for methanol-induced retinal toxicity provided scientific evidence that red and near-infrared light stimulates ATP production in cytochrome-c, a membrane-bound chromophore in mitochondria. This was a breakthrough in understanding PBM’s photochemical mechanisms rather than thermal effects.

Throughout the 20th century, PBM research primarily focused on static laser or LED applications, where light exposure was either continuous or pulsed under fixed conditions. The term “Photobiomodulation” was first used in 1997 but did not gain widespread acceptance until its official inclusion in the MeSH database in 2016.

Modern Advances in Photobiomodulation Therapy

The early 2000s saw a resurgence of interest in PBM, along with innovative approaches to light therapy. In 2001, PBM pioneer Dan Schell, founder of “Perfect Light” (APL), began experimenting with multi-wavelength LED configurations, varying illumination conditions and durations to develop precise, disease-specific treatment protocols.

In 2012, Schell collaborated with Richard K. Williams, an electrical engineer and semiconductor physicist specializing in molecular biology, nanotechnology, and photonics. Williams, a prolific inventor with over 350 patents, was the founding CEO/CTO of the Nasdaq-listed semiconductor company Advanced Analogic Technologies Inc. (AATI). His contributions to power semiconductors and photonic systems included LED camera flashes, dynamic LED backlighting for HDTVs, and advanced LED dimming technologies for smartphones.

By integrating APL’s treatment protocols with Williams’ expertise in biophotonics and semiconductor technology, and leveraging Ken Lin’s global manufacturing and operational experience, the team developed and launched the world’s first dynamically controlled and programmable medical-grade LED PBM biophotonics system.