Sunlight is a combination of visible light and invisible light. The seven colors of the rainbow are visible lights, and infrared rays and ultraviolet rays are invisible lights. Infrared rays are one of the sun's rays. Infrared rays penetrate into your skin deeply and they dissolve harmful substances accumulated in your body. The Infrared Rays vitalize your cells and metabolism.
Far infrared waves penetrate deep into our body for a deep heating action which allows for the body to activate the sweat glands. The sweat glands offer one of only a few mechanisms that the body has to eliminate toxins and since the skin is the largest organ in the human body it is a very good means for elimination.
When far infrared waves are applied to water molecules (comprising 70% of our body) these molecules begin to vibrate. This vibration reduces the ion bonds and the eventual breakdown of the water molecules causes encapsulated gases and other toxic materials to be released.
The efficacy of far infrared waves is very broad and the subject of recent study by NASA. Among the infrared waves, the far infrared rays, which have a wavelength of 8-14 microns, are especially good for the human body. These waves have the potential to penetrate 1.5 to 2 inches or more into the body allowing for deep heat and raising your core body temperature from deep inside. The deep heat and far infrared is why scholars believe that the Ondol (traditional warm floor of Korea) is good for health because the materials for the Ondol are stone and earth both of which radiate far infrared waves when heated.