How Saunas Work

Steam bathing is a truly ancient custom, dating back to the earliest nomadic tribes. As human culture sprang up like weeds around our physical needs, the notion of personal hygiene merged with those of purity and transformation. Depending on where you're coming from, a little time in the sauna can treat not only soreness or tension, but even spiritual pollution.

Yet amid all the intertwined vines of folklore and placebo effect, a chord of solid medical science supports the notion that, yes, a little time in the sauna is time well-spent. Sweating, no matter how detrimental to a job interview, is a part of healthy living.

This is how it goes down: The heat triggers sensitive nerve endings that release a neurotransmitter called acetylcholine, which kicks 2.3 million sweat glands into action. During the course of a 15-minute sauna, the average person can expect to shed a little more than 4 cups (1 liter) of sweat. Your body does this to control body temperature.

Sweating, like urinating, is a form of excretion and all forms of excretion help to rid the body of waste and/or toxins (though sometimes incidentally). Imaginative creatures that we are, this fact often leads to dodgy and outright false notions that bleeding or experiencing a bowel movement can heal any physical, mental or spiritual ailment.

Likewise, the idea of sweating out your troubles dates back to ancient times, but what does science have to say? In 2005, the U.S. Centers for Disease Control and Prevention (CDC) found that heavy sweat contains only trace amounts of bodily toxins, no matter how high levels are in the blood and urine. Take mercury, for instance: Less than 1 percent leaves the body in the form of sweat, while the rest goes out with the feces and urine [source: Woolston].

Still, sauna detox advocates put stock in this 1 percent and also point to the beneficial secretions of excess salt and uric acid or urea, which is normally handled by the body's big-league detox organs, the kidneys. This method again falls to the "let the kidneys handle it" counterargument, but when kidney function is impaired, sweating it out in a sauna can help to make up the difference.

Ironically, sweating to rid yourself of toxins can actually backfire if you don't remain properly hydrated. The kidneys need water to function, and your water-based urine is the vehicle by which substances such as urea leave your body. Rob your body of too much water and you could wind up impairing your core detox systems [source: Huang et al.].