Humans cannot see infrared light but they can feel it. Infrared light penetrates organic substances without warming the air around them. The heat from infrared light penetrates the skin deeper and more efficiently than other heating methods such as heating pads.
Heat therapy that employs infrared rays is thought to increase blood circulation without straining the heart. Some believe infrared light rays increase white blood cell and oxygen levels in the blood. In general, infrared light therapy is thought to promote a strong immune system and cardiovascular system. By causing the body to perspire, infrared light helps remove toxins in the body.
There are many practical applications for infrared light. Infrared light is sometimes used to help treat wounds and heal scars. Because this light penetrates so deeply into the skin, it is sometimes used in the treatment of arthritis pain. Some use infrared light to try to loosen stiff muscles and joints.