What is the science behind Red light therapy? Infared and low spectrum EM waves sounds fancy to some but is it more than heat and a red light bulb

Question

I have some scientific background and I own horses. So many therapies to alleviate pain in horses are available on the market that are not regulated by any scientific body. The benefit and the disadvantage of not being regulated by the FDA is that pet owners don't need rigourous scientific studies before we can try a product. If there is a scietific theory behind a therapy I'm willing to experiment with my horse when I've exhausted all other know forms of therapy. However, I'm not understanding the red light therapy science and the $1000 price tag for a device. Is it a snake oil product? Looks like you can achieve the same infared and low spectrum radiation with a heating pad and a red light bulb.

Answer 1

Visible light is one example of an electromagnetic wave, although electromagnetic waves also go beyond the visible spectrum and include infrared and ultraviolet radiation (and, to be comprehensive, radio waves, microwaves, X-rays etc. as well).

The only things you can vary with an electromagnetic wave are its wavelength (which also determines its frequency) and its intensity. So red light is red light is red light - the only difference between a red light bulb and a more expensive source is that the more expensive source may produce a higher intensity of red light. But with visible light higher intensity makes little difference to its biological effect since visible light does not penetrate more than a few millimetres into skin at most. Even the most intense visible light from a laser, for example, could only penetrate further into the body if it damaged the surface layer of skin, which is obviously a bad idea.

Infrared radiation (beyond the red end of the visible spectrum) is a little different since it heats the outer layers of the skin, and this heat can then be conducted deeper into underlying muscles, tendons etc. But high intensity infrared radiation is also more dangerous than visible light since too much heating can cause skin damage and burns.

This page at Healthline concludes that there is some evidence (although not enough to form a scientific consensus) that red light therapy may promote healing of scars and other skin conditions, but no evidence for claims that it relieves underlying muscular or skeletal pain, boosts the immune system, cures cancer etc. (Note that this Healthline page discussed red light therapy on its own - medical treatments that use light of various wavelengths to activate photosensitive drugs are a separate subject).