For thousands of years, people have emerged from saunas feeling cleaner, lighter and refreshed. Long before science understood how the body's detoxification systems actually work, it was a perfectly reasonable assumption that all that sweat must have been helping to carry unwanted substances away.
It's an idea that has proved remarkably durable. Even today, you'll still see detoxification described as one of the benefits of sauna use by some manufacturers and retailers. The problem is that the word "detox" means different things to different people. In everyday conversation, it often refers to feeling cleansed or refreshed. In medicine, however, detoxification has a much more specific meaning.
Sweat can and does contain small amounts of certain unwanted substances, so it isn't wrong to say sweating contributes to detoxification. But the contribution is tiny compared with the work being carried out continuously by your liver, kidneys, gut and lungs.
None of this makes saunas any less worthwhile. If anything, it helps separate their genuine, evidence-backed benefits from one of the most persistent myths surrounding them.
What detoxification really is
Detoxification is a continuous process. Your body doesn't wait for a special diet, a cleanse or a burst of exercise. Every minute of every day, your liver, kidneys, gut and lungs are processing and removing waste products.
Those organs each have a different role:
- Liver - often described as the body's chemical processing plant. It transforms drugs, alcohol and many environmental chemicals into forms that can be safely eliminated.
- Kidneys - your primary filtration system. They continuously remove waste products from the bloodstream and concentrate them into urine.
- Gut - many substances processed by the liver are released into bile before leaving the body in stool.
- Lungs - with every breath you exhale carbon dioxide, the largest waste product produced by normal metabolism. The lungs also remove small amounts of volatile compounds such as alcohol and acetone.
Together, these organs perform almost all of the body's detoxification.
Where sweating fits in
The primary purpose of sweat is to regulate body temperature.
As sweat evaporates from your skin, it carries heat away from the body, preventing you from overheating during exercise, hot weather or a sauna session. That's what sweat glands evolved to do.
So where does the idea of "sweating out toxins" come from?
Sweat isn't made from nowhere. Sweat glands draw fluid from the bloodstream and, as that fluid is produced, tiny amounts of certain substances can pass into it. That's why researchers are able to detect trace amounts of some metals and environmental chemicals in sweat.
Researchers have consistently found that this is the case. As one review concluded:
"Arsenic, cadmium, lead, and mercury may be excreted in appreciable quantities through sweat."
At first glance, that sounds like strong support for the idea that sweating is an important detoxification pathway. But detecting a substance in sweat tells us that it can leave the body that way. It doesn't tell us how important that route is compared with the liver, kidneys, gut and lungs.
If your liver and kidneys are industrial pumps draining a swimming pool, sweat is a teaspoon scooping out water alongside them. The teaspoon is removing water too, just not in meaningful quantities.
How do substances end up in sweat?
The fact that sweat contains trace amounts of certain substances raises an obvious question: if sweat isn't designed to remove waste, how did they get there in the first place?
It comes down to how sweat is produced.
Many substances enter the body through the food we eat, the water we drink, the air we breathe or, in some cases, through contact with our skin. Once in the bloodstream, they circulate throughout the body.
Sweat glands draw fluid from that circulating blood. As the sweat forms, tiny amounts of some water-soluble substances can pass into it before it reaches the surface of the skin.
That's why researchers are able to detect trace amounts of certain metals and environmental chemicals in sweat. It isn't because sweat glands are designed to remove toxins. It's simply a consequence of how sweat is formed.
Compared with urine, however, the amount removed this way is extremely small.
What about the lungs?
The lungs also play an important role in detoxification.
Every time you breathe out, you remove carbon dioxide, the largest waste product generated by normal metabolism. Without that continuous exchange, life simply wouldn't be possible.
The lungs also eliminate small amounts of volatile substances, including alcohol and acetone. Compared with carbon dioxide, those quantities are tiny.
Does showering wash toxins away?
After a sauna, showering removes sweat, oils, bacteria and anything else sitting on the surface of your skin.
If trace substances have been carried out in your sweat, washing them away is perfectly sensible from a hygiene point of view.
What it doesn't do is increase or accelerate the body's detoxification processes. Those have already taken place before the sweat reached your skin.
Other ways the body removes small amounts of substances
Sweat isn't the only way small quantities of substances leave the body. Several other pathways contribute too, although each plays a relatively modest role.
- Hair and nails, which can incorporate certain metals as they grow.
- Shedding skin cells, which are continuously replaced throughout life.
- Menstruation, which may eliminate small quantities of some substances.
- Breath, beyond carbon dioxide, which can carry small amounts of alcohol and other volatile compounds.
These pathways are real and measurable, but they all make relatively small contributions compared with the liver, kidneys, gut and lungs.
The bottom line
So where does that leave the familiar idea of "sweating out toxins"?
The answer is that sweating does contribute to detoxification, but only in the most modest of ways. Tiny amounts of certain substances can leave the body in sweat, and there's good scientific evidence demonstrating that they do.
What sweating doesn't do is replace or significantly augment the body's primary detoxification systems. That job is performed continuously by your liver, kidneys, gut and lungs.
Saunas have plenty of genuine, evidence-backed benefits. There's good evidence that regular sauna use can support relaxation, exercise recovery, overall wellbeing and, for some people, cardiovascular health. Those are compelling reasons to use a sauna in their own right. We don't think those benefits need to be exaggerated by relying on claims that don't accurately reflect how the body actually works.
References
- Genuis SJ, Birkholz D, Rodushkin I, Beesoon S. Blood, urine, and sweat (BUS) study: monitoring and elimination of bioaccumulated toxic elements. Science of the Total Environment. 2011;409(23):5339-5348. https://doi.org/10.1016/j.scitotenv.2011.02.001
- Sears ME, Kerr KJ, Bray RI. Arsenic, cadmium, lead, and mercury in sweat: a systematic review. ISRN Toxicology. 2012;2012:184745. https://doi.org/10.5402/2012/184745
- Genuis SJ, Beesoon S, Birkholz D, Lobo RA. Sweat facilitated elimination of toxic elements. Journal of Environmental and Public Health. 2012;2012:184745. https://doi.org/10.1155/2012/184745
- Farhi LE, Edelman NH. Pathophysiology of body water and electrolyte regulation during heat stress. Annual Review of Medicine. 1980;31:1-16. https://doi.org/10.1146/annurev.me.31.020180.000435
