Near- infrared light and far-infrared light. The two are often confused as the same thing but they are really quite different.
Infrared (IR) means "beyond (further on/near) red". It begins just after the visible red light on electromagnetic spectrum. It was discovered in 1800 when a British astronomer created an experiment to measure the difference in temperature between the colors. He placed thermometers in the path of light within each color and found even warmer temperature measurement beyond the red end of the visible spectrum.
Infrared radiation is divided into three spectral bands, based on wavelength: near-, mid- and far-infrared. However, the measurements and boundaries between each infrared region vary slightly and so far, there is no consensus on uniform boundaries.
Near Infrared (NIR)
Near-Infrared is the light used in Red Light Therapy.
It is the closest to the red end of the visible light spectrum with wavelengths measuring roughly 750 nanometers (nm) to about 1,300nm that are microscopic in size. It has the shortest frequencies compared to the other regions. Unlike Far Infrared, NIR waves do not produce any heat. In fact, we can't feel them at all.
NIR is the light that triggers a natural photo-biochemical reaction which promotes cell health, skin renewal, wound healing, tissue growth and all those wonderful things Red Light Therapy is known for.
Mid Infrared (MId-IR)
Mid-Infrared is defined as the region between near and far infrared and has a wavelength range of about 1,300nm to 3,000nm This type of infrared gives off moderate heat compared to the near and far-infrared regions and does not have any healing powers.
Far Infrared (FIR)
Far Infrared, also known as thermal infrared. This is the largest part of the IR spectrum. This is what is used in infrared saunas.
In the electromagnetic spectrum, FIR waves lie farthest to the red and closest to the microwave region. It has a wavelength range of 3,000nm to 10,000nm, The far-infrared region has the longest frequencies, which produces the most heat. These are thermal waves which are not visible to the eye and make up the heat we feel when we're near the fire or standing in the sunlight.
FIR light has been discovered to have therapeutic properties. It’s waves can help to detoxify the body, restore energy and burn calories. Its units help to promote toxin release through profuse sweating. FIR only provides a heating effect on the cells but does not activate any cellular regenerative or anti-aging systems of healing.
Now. The question.
We already learned here that the longer the wavelength of light, the deeper the tissue penetration, so how come NIR (with only 750nm to about 1,300 nm) goes more than 5 times deeper into our body than FIR (which starts at 3,000nm)?
The answer is simple: our body can absorb only one narrow band of light between 600nm and 1150nm. It probably wouldn’t mind to get more but everything below 600nm (which is all visible light basically except red) is absorbed by hemoglobin, and water steals all light above/greater than1150nm! Considering water accounts for about 60% to 70% of our body weight, its molecules stop far infrared light from penetrating into our tissues. Even when FIR light manages to get into human tissue, it doesn’t carry the same benefits as NIR.
Far Infrared light is less clinically effective and quite different than Near-Infrared. While both lights offer very different benefits and treatments, they can both help us and can easily co-exist!