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Visible vs. Infrared Lasers

red light therapy

There is so much misinformation about the science of low-level lasers and how manufacturers have manipulated the science to gain a sales advantage – it is hard to separate fact from fiction. One example is; that longer wavelengths penetrate deeper. However, this “marketing claim” is backed by no clinical research and goes against the established physics of light. Published literature demonstrates that depending on the laser wavelength either a photochemical or photophysical reaction will occur.


The first law of Photochemistry states, that the energy in the photon (electron volt or EV) has to be absorbed by the cell to create a photochemical effect in the body. Photochemical reactions in tissue only occurs with visible light, this is well known and has been published in many papers and scientific journals. Visible light (400nm – 660nm) has sufficient energy to displace electrons in atoms to a higher energy state, without causing ionization. Once the energy inside the cell is absorbed the cell then uses what energy it needs then passes the excess energy to the next cell. The more energy (ev) the photon has the more energy it has the pass on to the next cell, then the next to create a stronger photochemical effect. For this reason, high energy photons from visible light are capable of creating greater systemic effects than longer wavelengths, since the initial electron charge is higher the more transfer of elections is possible

The easiest way to understand how photochemistry works would be to look at biochemistry or how drugs work. If you are taking 200mg of a drug like an NSAID you swallow the pill, it enters your stomach and after your stomach starts to break down the drug it starts a biochemical response that reduces inflammation. There is a therapeutic dose that is most optimal, by increasing the dose all you are doing is increasing milligrams and the side effects. Biochemical responses are not natural, unlike laser light which is natural and with visible light there are no known side effects.  Each wavelength of visible light (red, blue, green) will produce a distinct photochemical effect, through similar, if not the same biological pathways of pharmaceutical drugs. Published research from The University of Chicago Illinois (UCSD) and other Universities using the Erchonia laser, that depending on the condition there is a peak wavelength absorption for simulating the desired biological pathways such as reducing apoptosis, necrosis, TNF-a, mitochondria production, stem cells, nerve regeneration, immune function, etc. 

Infrared Lasers (Photophysical Effects)

Infrared Light (IR) is not energetic enough to initiate photochemical processes, instead, the result of infrared absorption is heat formation due to a increase in molecular vibrational activity, this is referred to photophysical effect. For direct photochemistry to occur, it is reported the (eV) must be 1.7eV, equal to 730nm. In fact, since the photon energy is so low in the IR wavelengths, the light is strongly absorbed by water molecules leading to superficial heating of the skin (Georgia State University), which is contrary to the propaganda that manufacturers state that these wavelengths penetrate deeper than visible light.

The longer the wavelength 730nm-12,000nm the less energy (ev) in the photon.  By increasing the laser power all you are doing is shooting out less energetic (ev) photons. Again, the shorter the wavelength the more energy the photon, when you get below 380nm there is so much energy in the photon that the body does not absorb the energy and the photons bounce off the bone which is how x-rays work. These lower wavelengths are so energetic they are referred to as ionizing radiation and due to the high energy photons, they can cause cancer. 

Infrared lasers are absorbed by the water in the upper layers of the tissue, the water starts vibrating and slowly starts a warming reaction by the cells vibrating in humans and plants. By increasing the power of the laser all you are doing is heating the tissue faster.  Tissue ablation works by increasing power in microseconds to the point where you are killing the upper layers of the dermis (apoptosis) for skin rejuvenation. Increasing power does not increase how far the laser penetrates unless you are measuring how deep the heating of the tissue will reach. 

Contact our Erchonia team if you would like more information on low level laser therapy.

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