Red and near-infrared light is a narrow spectral between 600nm – 1000nm. The fluence (energy density) used is generally between 1 and 20 J/cm2 while the irradiance (power density) can vary widely depending on the actual light source and spot size; values from 5 to 50 mW/cm2 are common for stimulation and healing. Higher dosage will be used for pain relief.
Photobiomodulation is efficacious to promote tissue regeneration, reduce swelling and inflammation and relieve pain. Within a matter of a few seconds light is delivered deep inside tissue, and triggers biochemical responses at the molecular level.
By definition, photobiomodulation is not a thermal mechanism - it does not create heat. That simple distinction differentiates it from other light therapies that attempts to generate different responses. The photochemical effect elicited by photobiomodulation is comparable to photosynthesis in plants.
Red and near-infrared light is absorbed by cytochrome c oxidase, or CCO, a photosensitive enzyme found within the mitochondria. The mitochondria is the energy-making machine that sits at the core of our cells. The CCO absorbs the light, converts it to energy that in turn triggers a biochemical response that enhances the efficiency of the cell.
Biphasic Dose Response
More is not better.
As we are gaining a better understanding of how photobiomodulation operates at the cellular level, we can explain how a little light may be beneficial and a lot of light might be impotent or harmful.