Scientists have established that infrared waves are beneficial to the human body because they are easily absorbed, stimulating the lymphatic, immune and cardiovascular systems and also help remove toxins. The sun produces a combination of visible and invisible light, and one of those invisible spectrums is infrared rays. Invisible infrared wavelengths are what makes the sun feel warm (and ultraviolet wavelengths are what makes it bright). Infrared does all of this without any of the harmful rays of sunlight. 

Unlike a traditional steam sauna, which heats the surrounding air inside the cabin, infrared heats the body directly. Air temperature in the sauna is not as important as the type and quality of the infrared being received.