Can You Sweat Out Microplastics? What Sauna and Sweat Studies Measured

Can you sweat out microplastics?

The idea sounds reasonable. Sweat comes out of the skin, saunas make a lot of it, and some people with large followings say heat helped lower their test results. Our look at Bryan Johnson’s routine covers his specific sauna claims. This page answers the general question: does sweat carry plastic out?

Sweat is mostly water. National Geographic summarizes it as more than 99% water with small amounts of salts, urea, lactic acid and proteins. It is made by sweat glands that draw fluid from the blood around them. A solid plastic fragment would have to get out of the blood and through the gland to show up in it. That route has not been studied for microplastics. In the sources we reviewed, nobody has collected sweat and counted particles in it, so the honest answer is that it is unknown, with no evidence that it happens to any useful degree.

What the sweat studies actually measured

The research usually quoted on sauna detox comes from one Canadian group led by Stephen Genuis, called the Blood, Urine and Sweat (BUS) studies. Each recruited 20 people from the lead author’s practice, half healthy and half with health problems. Participants sweated in an infrared sauna, a steam sauna or during exercise, and collected about 100 mL of sweat into glass jars.

The BPA study found BPA in sweat at about 10 to 82 ng/mL, with some people showing it in sweat but not in urine or blood. The authors suggested that blood and urine tests may underestimate exposure and that induced sweating may help remove BPA. The phthalate study found MEHP, a breakdown product of the plasticizer DEHP, in every sweat sample, and the parent DEHP in 11 of 18 sweat samples even though none of those people had it in their blood. The 2016 pesticide study used the same design for older pollutants.

These results are real and worth knowing. They show plastic chemicals can appear in sweat. They are not microplastics, and they are not evidence that sweating reduced anyone’s levels, because no one was measured before and after a course of sauna use.

Why BPA in sweat does not make sauna a plastic detox

The body already clears BPA quickly. CDC’s biomonitoring summary says the processed form of BPA is excreted in urine within 24 hours, with no evidence it builds up. For a short-lived chemical like this, what you take in each day matters far more than how you get rid of it.

The amounts may be small. In a 2018 commentary, researchers led by Pascal Imbeault questioned whether sweating removes meaningful amounts of persistent pollutants. Imbeault told National Geographic that about 2 litres of sweat would carry roughly 0.02% of what a person takes in daily from a typical diet. That estimate covered persistent pollutants such as PCBs, not BPA, so it is not a direct figure for plastics. It does show why “found in sweat” and “removed in a meaningful amount” are separate claims.

Sweat collected from skin can pick up what is on skin. The phthalate authors argued contamination was unlikely because results were consistent, but they did not test skin blanks. BPA and phthalates are common in receipts, lotions, fragrances and fabrics, so a sweat sample scraped from the body can mix what the body excreted with what was sitting on it.

What a real test would look like. To show that sauna removes plastic, researchers would need to measure the same people before and after weeks of sessions, compare them with a similar group that did not use a sauna, keep diet and containers steady, collect sweat with skin-cleaning and blank controls, and count particles as well as chemicals. None of the studies above did that. Until someone does, the sweat detox claim is a hypothesis built on chemical detections.

Has anyone found microplastics in sweat?

Not in the studies we reviewed. The closest research runs the other way. University of Birmingham scientists put flame-retardant-laden microplastics into synthetic sweat and found the sweat leached chemicals out of the plastic. A 2024 follow-up on lab-grown human skin models found those chemicals could then be absorbed through skin. That is plastic in contact with sweat, outside the body, giving up its additives. It is a reason to wonder about synthetic gym clothes, not evidence that sweating pushes particles out.

Intact skin is a good barrier against particles from the outside; what can cross is mostly a question of size. Our skin absorption guide covers what is known about particles and chemicals going in.

How do microplastics leave the body?

Most swallowed particles are thought to pass straight through the gut and leave in stool, which is where the best evidence sits. Schwabl and colleagues found microplastics in stool from all eight volunteers in 2019, a median of 20 particles per 10 g, mostly polypropylene and PET, between 50 and 500 µm. A larger 2022 study by Yan and colleagues found 41.8 particles per gram of dry stool in people with inflammatory bowel disease and 28.0 in healthy people. The authors could not say whether plastic worsens the disease or the disease makes people retain more plastic.

Urine is a smaller route. Pironti and colleagues found microplastics in urine from 4 of 6 volunteers in Italy in 2022, seven fragments in total, about 4 to 15 µm. Particles small enough to reach blood and organs may stay much longer, and no study has measured how long. Our guide to how long microplastics stay in the body covers that evidence.

Saunas and exercise: worth doing, not for this reason

Regular sauna and exercise have been studied for heart health, mood and fitness. A 2018 systematic review by Hussain and Cohen found a range of possible benefits from dry sauna but noted the detox evidence leaned on weaker, often subjective outcomes. Saunas also have costs. A small 2013 study of ten men found repeated sauna sessions lowered sperm count and motility, which recovered after they stopped. Heat stress, dehydration and some medicines do not mix well.

So if you like the sauna, keep it. Drink water, stay within comfortable limits and talk to a clinician if you have heart conditions, take relevant medication or are trying to conceive. Just do not go longer or hotter to chase plastic out. Our detox guide covers the other popular methods and what each one has, and has not, shown.

Is the sauna itself a plastic source?

Possibly, in small ways, though we found no study measuring particles in sauna air or from sauna blankets. Heat speeds the release of chemicals from many plastics, which is why a plastic bottle that sits in a hot room is a poor choice. See our hot car water bottle guide for what heat does to bottled water. Practical steps: bring water in glass or stainless steel, sit on a cotton or linen towel rather than a synthetic one, and if you use an infrared blanket or pod, ask the maker what the inner layer touching your skin is made of.

Use the App

Find the plastic you can actually cut

Scan the bottles, containers and packaged foods you use most. The app shows declared or estimated materials, flags likely BPA or phthalate sources, and saves lower-plastic swaps. It does not measure plastic in your body or track detox.

What actually lowers your exposure

The strongest evidence is on the input side. In a 2011 study, five families ate fresh, unpackaged food for three days. Their urinary BPA fell 66% and DEHP metabolites fell 53 to 56%, and BPA rose again when they went back to their usual diet. That measured chemicals, not particles, but it shows how fast levels follow intake. For particles, lab studies like Yadav’s 2023 cutting-board work point to everyday contact surfaces.

If you want a structured week of these swaps, our 7-day exposure audit lays out one change a day. Start with the food or drink container you use most often. It will do more than an extra 20 minutes in the heat.