Can you sweat it out? Alcohol, THC, nicotine, caffeine, a cold, a fever and toxins
Sweat is for cooling. Here is what researchers have measured in it, substance by substance, where each one actually leaves the body, and what a long sauna session adds instead.
Short answer: Mostly no. Sweat exists to cool you, and a 2019 review of sweat gland physiology found its role in clearing waste and toxicants is minor next to the kidneys and gut. About 1% of the alcohol you drink leaves through the skin. THC, nicotine and caffeine are cleared mainly by the liver, kidneys and gut, with only traces in sweat. A sauna will not shorten a hangover, a cold or a fever. What heavy sweating does remove is water and salt.
“Sweat it out” is old advice, applied to everything from a big night to a cold. It sounds physical, because you can feel something leaving.
What leaves is mostly water. This guide goes substance by substance through what researchers have measured in sweat, where each substance actually leaves the body, and what a long sauna session adds instead.
This is general information, not medical advice. If you are worried about an illness, a medicine or how much you drank, a doctor or pharmacist is the right person to ask.
Why sweat cannot carry much out
Sweat glands are built to cool you, not to filter your blood. A 2019 review of sweat gland physiology by Lindsay Baker in Temperature concluded that “the role of sweating to eliminate waste products and toxicants seems to be minor compared with other avenues of excretion via the kidneys and gastrointestinal tract.”
The reason, the review explains, is that sweat glands do not adapt to excrete more, either by concentrating sweat or by raising the overall sweating rate. Studies suggesting a bigger role may reflect problems with how sweat was collected, such as contamination from the skin, rather than real transport.
The review also notes where the belief leads: some people seek out heavy sweat losses, prolonged sauna sessions among them, for health benefits they expect from the sweat itself. That habit is what this guide tests, one substance at a time.
Can you sweat out alcohol?
No. About 90% of the alcohol you drink is removed by oxidation, mostly in the liver, and less than 10% leaves unchanged through breath, sweat and urine combined, according to a 2012 review of alcohol metabolism by Cederbaum.
The skin’s share is small. Transdermal alcohol sensors, such as the ankle bracelets used to monitor drinking, measure “the approximately 1% of ingested alcohol that is excreted through the skin,” as Barnett and colleagues put it in 2011.
Heat does not change that arithmetic. The Baker review lists no effect of alcohol on sweating rate, and the alcohol concentration in sweat simply rises with the alcohol in your blood.
What heat does change is the risk. A 2001 review of sauna bathing in The American Journal of Medicine found that alcohol during sauna bathing increases the risk of low blood pressure, arrhythmia and sudden death, and should be avoided. Our guide to drinking in a sauna covers why.
Can you sweat out a hangover?
Sweating does not clear the alcohol faster, as above, and there is no proven cure to sweat toward. A systematic review in the BMJ in 2005 assessed eight randomised trials and concluded that “no compelling evidence exists to suggest that any conventional or complementary intervention is effective for preventing or treating alcohol hangover.”
A hot room adds more fluid loss through sweat on top of the night before. Our guide to hangover cures goes through the sauna, cold water and IV drips one by one.
Can you sweat out THC?
Not in any amount that matters. THC does show up in sweat, which is why sweat patches can monitor cannabis use. In a 2008 study by Huestis and colleagues, 11 daily cannabis users wore patches after they stopped, and their first-week patches averaged 3.85 nanograms of THC each. A nanogram is a billionth of a gram.
The bulk leaves another way. Huestis’s 2007 review of cannabinoid pharmacokinetics reports that more than 65% of THC is excreted in the feces and about 20% in the urine, mostly as metabolites.
Our guide to sauna and cannabis covers the real risk, which is fainting as you stand up to leave the heat.
Can you sweat out nicotine?
Barely. In a review of nicotine metabolism by Benowitz, Hukkanen and Jacob, 70 to 80% of nicotine is converted to cotinine, and the liver enzyme CYP2A6 is the main route. The kidneys also clear some nicotine unchanged: about 5% of total clearance when urine pH is not controlled.
Nicotine and cotinine do reach the skin. The same review notes that hair is exposed to them through sweat, which complicates hair testing. A trace on the skin is not a route of clearance, though.
If you wear a nicotine patch, heat matters for a different reason: in a small study, a sauna raised peak nicotine levels from the patch. Our guide to heat with a medicated patch covers what the labels say.
Can you sweat out caffeine?
No. Caffeine is broken down in the liver, where the enzyme CYP1A2 does the work. The FDA label for caffeine citrate gives the adult figures: a half-life of about 5 hours, with about 1% leaving unchanged in the urine.
So even the kidneys pass very little caffeine unchanged, and the Baker review found that sweat glands do not adapt to excrete more when you sweat more. Waiting it out is the only clearance there is.
Our guide to caffeine before a sauna covers what caffeine does to your heat tolerance, which is the question that matters in the hot room.
Can you sweat out a cold?
No. A cold is a viral infection that runs its course. MedlinePlus says most colds go away in a few days and most symptoms within a week, and its self-care advice is plenty of rest and fluids. It adds that over-the-counter medicines can ease symptoms but do not make a cold go away faster.
The sauna study people cite is about prevention, not a cure. In a small trial by Ernst and colleagues in 1990, people who used a sauna regularly reported fewer colds than controls, with the difference showing in the second half of the six-month study. That is a habit over months, not a session while you are ill.
Our guide to using a sauna when you are sick covers when to stay home.
Can you sweat out a fever?
No, and the standard advice runs the other way. MedlinePlus’s fever guidance says not to bundle up someone who has chills, to remove excess clothing or blankets, and to keep the room comfortable, “not too hot or cool.” It also says the goal is to lower, not eliminate, the fever.
A fever already raises your core temperature, and a sauna is built to raise it further. Our sick-day guide explains why a fever is the clearest reason to skip the heat.
Can you sweat out toxins?
Some do show up in sweat. The study usually cited, by Genuis and colleagues in Archives of Environmental Contamination and Toxicology, measured toxic elements in blood, urine and sweat and found some of them in sweat.
Present is not the same as cleared. The Baker review found the role of sweating in eliminating toxicants “seems to be minor” next to the kidneys and gut, and that studies suggesting a larger role may be an artifact of methods.
Our guide to whether sweating detoxes your body covers the claim in full.
What sweating does take out
Water first and sodium second. In the measurements our electrolytes guide draws on, sweat carried about 4 times more sodium than potassium. The Baker review found that sweat-induced deficiencies of trace minerals and vitamins appear to be a minimal risk.
The simplest way to see your own loss is the scale. Weigh yourself before and after a session, without clothes or a damp towel, and drink back the difference over the next hour or two. Our sauna sweat loss calculator does the arithmetic.
Sweating it out at a glance
| Substance or illness | In sweat? | Where it mostly goes | Source |
|---|---|---|---|
| Alcohol | About 1% of what you drink leaves through the skin | About 90% removed by oxidation, mostly in the liver | Cederbaum 2012; Barnett 2011 |
| THC | Traces: billionths of a gram per patch | More than 65% in feces, about 20% in urine | Huestis 2007 and 2008 |
| Nicotine | Enough to reach hair | 70 to 80% converted to cotinine; about 5% of clearance unchanged through the kidneys | Benowitz 2009 |
| Caffeine | Not measured in these sources | Broken down in the liver; about 1% unchanged in urine | FDA caffeine citrate label |
| ”Toxins” | Some, in small amounts | Kidneys and gut; sweat’s role “seems to be minor” | Baker 2019; Genuis |
| A cold | Not a substance | Runs its course; most symptoms gone within a week | MedlinePlus |
| A fever | Not a substance | Do not bundle up; keep the room comfortable | MedlinePlus |
FAQ: can you sweat it out?
Can you sweat out alcohol in a sauna? No. About 90% of alcohol is removed by oxidation, mostly in the liver, and only about 1% leaves through the skin. Alcohol also makes a sauna more dangerous: a medical review found it raises the risk of low blood pressure, arrhythmia and sudden death.
Does sweating get rid of a hangover? No. A BMJ review of eight trials found no compelling evidence that any intervention prevents or treats a hangover, and a hot room only adds fluid loss through sweat.
Can you sweat out THC? No, not in any amount that matters. Sweat patches from daily users held THC in billionths of a gram, while more than 65% of THC leaves in the feces and about 20% in the urine.
Can you sweat out nicotine? Barely. Most nicotine is converted to cotinine, mainly by a liver enzyme, and some leaves unchanged through the kidneys. Nicotine reaches the skin in sweat, but only as a trace.
Can you sweat out caffeine? No. Caffeine is broken down in the liver, and the FDA label for caffeine citrate gives an adult half-life of about 5 hours, with about 1% leaving unchanged in urine.
Can you sweat out a cold? No. MedlinePlus says most colds go away in a few days, most symptoms within a week, and advises rest and fluids. A small 1990 trial linked regular sauna use with fewer colds over months, which is prevention, not a cure.
Should you try to sweat out a fever? No. MedlinePlus says not to bundle up someone who has chills, to remove extra blankets and to keep the room comfortable. A sauna would push your temperature up, not down.
Does sweating remove toxins? Some toxic elements have been measured in sweat, but a 2019 review found sweat’s role in clearing toxicants “seems to be minor” next to the kidneys and gut.
The bottom line on sweating it out
Sweat cools you; the liver, kidneys and gut clear what you take in. A sauna can be worth using for other reasons, but it will not sober you up, end a hangover, clear THC, nicotine or caffeine, or burn off a cold or a fever.
If you want to know what a session really costs you, weigh yourself before and after. That number is water, and drinking it back is the job.