What Toxins Do Infrared Saunas Remove Through Sweat? The Evidence Says Less Than You Think

If you’ve spent more than ten minutes in wellness circles, you’ve heard the claim: sweat it out in an infrared sauna and you’ll purge heavy metals, BPA, and phthalates from your body. Detox, the marketing says, is a matter of getting hot enough.

Ask a medical researcher, though, and you’ll often get the opposite: your liver and kidneys handle detoxification, not your sweat glands, and anyone telling you otherwise is selling something.

Which one’s right?

Here’s what the science shows, including a 2022 study that had the same people sweat two different ways, and compared the metals that came out. The finding: four of the five metals measured came out at higher concentrations during exercise than in a sauna. The study, published in the International Journal of Environmental Research and Public Health, wasn’t complicated. Twelve healthy young adults, five metals, 24 sweat samples. The twist is what the sweat contained.

The five metals that actually show up in infrared sauna sweat

If you glare at a sauna long enough, science will eventually look for heavy metals in your sweat. These are the five researchers have found there: nickel, lead, copper, arsenic, and mercury.

In a 2022 crossover study out of Taiwan, 12 healthy university students sweated under both conditions, a treadmill run and seated time in a sauna cabinet, and the researchers measured what came out. For four of the five metals, exercise produced higher concentrations: nickel, lead, copper, and arsenic were all significantly higher in during-exercise sweat than in sauna sweat (statistically significant at p < 0.05).

Mercury was the exception, showing no difference between methods.

A few caveats worth noting. Copper isn’t a “toxin” on its own, your body needs it for life, though too much can be toxic. And while some of these metals do appear in sweat, the amounts are small. The lab’s detection limits tell the story: they could reliably detect nickel down to 1.1 micrograms per liter, lead at 3.0, copper at 1.5, arsenic at 0.03, and mercury at 0.05. The fact that these metals showed up at all, and that detection limits needed to be this sensitive, tells you how trace-level these concentrations are.

That said, some metals do concentrate in sweat compared to other body fluids. Nickel, lead, and chromium in sweat have been reported at 10-30 times their levels in blood or urine, so sweat is a meaningful route of excretion for them.

Exercise vs. sauna: which sweat removes more metals?

The running sweat won. Four metals out of five.

Here’s what that 2022 study did. Participants were divided into two groups. On the first day, one group ran on a treadmill at 25°C and 40% humidity; the other sat in a sauna cabinet at 45°C and 40% humidity. On the second day, they swapped. Each person, in other words, sweated under both conditions, once running, once sitting in heat.

Both groups sweated at the same rate: about 1.8 milligrams per square centimeter per minute. That distinction matters for the mechanisms, but the short version is that matching the sweat rate isolates the data from the conditions.

The result: nickel, lead, copper, and arsenic concentrations were higher during exercise. Mercury stayed about the same regardless of method.

One calibration point: this is a single small study (12 participants), not a jury verdict on all saunas everywhere. Taiwan’s environmental lead and copper levels tend to run higher than in Western countries, and the researchers noted that women in this study showed higher baseline nickel (81.0 ± 35.2 μg/L versus men’s 33.5 ± 54.3), which may have skewed the comparison.

But the core finding stands: if heavy-metal excretion is the goal, the evidence points to movement over passive heat.

Why sauna sweat is more dilute than exercise sweat

Here’s the counterintuitive part: you sit in a sauna and you pour sweat, and that sweat carries less of the metals you’re after.

The reason has to do with thermoregulation. When you run, your core temperature rises, it can reach close to 40°C during long efforts. Your body responds by jacking up your heart rate and pushing warm blood toward your skin, where the blood is then cooled by sweating. Because that blood is circulating fast, it carries more of whatever’s dissolved in it, including metals, out to your skin with it.

A sauna is different. Your core temperature rises only slightly, by about 1°F (0.75°C) when a person stays in a 46°C room for four hours. When ambient heat is doing the work, your body doesn’t need to mount the same adaptive response. It produces sweat by a more passive route, which ends up more like a large wet towel than a metal transport system. Notably, infrared-induced sweat contains higher concentrations of heavy metals and fat-soluble toxins, as the deep tissue heating appears to mobilize these substances.

That’s why sauna sweat is more dilute. Your body is trying to cool you down, not flush metals out of your bloodstream. The composition difference shows up in the numbers: sauna sweat had lower concentrations of nickel, lead, copper, and arsenic than exercise sweat in the 2022 study, though infrared sauna sweat can still carry heavy metals and toxins that aren’t found in blood or urine.

BPA and phthalates: what the sweat really shows

Two research groups tried to answer the same question about BPA in sweat, and got opposite answers.

The difference comes down to how they collected the sweat.

Active sweating vs. passive patches: why the numbers conflict

In 2015, researchers at the University of Alberta had 20 participants sweat by bag-wrapping their forearms after exercise. The results showed BPA in the sweat of 14-16 of 20 participants, even when blood tested negative for BPA. They also found phthalate metabolites at about double urine concentrations, and a parent compound called DEHP that appeared in sweat but not in serum, which they suggested pointed to tissue-level accumulation being mobilized through perspiration, a mechanism also implicated in the elimination of heavy metals and environmental toxins.

In 2015 (verify year against source), a different team at Washington State University used a different method: participants wore passive patches on their skin for a week, then had those patches analyzed.

This time, BPA showed up in only 3 of 386 patches, a different result. But urine samples told a different story: BPA appeared in 340 of 386 samples.

So which is right?

Both. The difference is the method. Active sweating induced by exercise or heat produced measurable BPA in sweat. Passive accumulation of skin oils over a week produced almost none. You’re looking at two different processes, and conflating them is the root of many “sauna removes BPA” headlines.

What this means for the sauna claim on BPA

BPA can appear in actively induced sweat, that much is real. But the collection method matters, so a lot of the “sauna removes BPA” claims overstate what the literature actually supports.

If your real question is, “will a sauna meaningfully lower my BPA load?” the evidence says no. The amounts are too small to move the needle, and far more BPA leaves your body through urine anyway. The best way to reduce BPA exposure is to steer clear of containers made with it when choosing what to eat or drink.

Why sweat-toxin studies disagree: the contamination problem

Here’s the reason conflicting headlines about sweat detox keep multiplying: many studies have a hidden contamination problem.

To collect sweat for analysis, researchers scrape it from skin. That scraping also picks up skin flakes, lipids, and whatever residue is on the surface, and that contamination can inflate metal readings. One 2019 review found that skin-scraped sweat collected this way contains 4-10 times more lipid than you’d expect from pure sweat, throwing off measurements.

The 2022 study guarded against this with a detail most coverage skips: they filtered the samples through a 0.22-micron syringe filter before analysis. That pore size catches skin flakes (which are larger than 10 microns) while letting the liquid through, so they were actually measuring the metals dissolved in sweat, not surface debris.

This same failure mode explains why studies looking at the same metal get wildly different numbers. One group measured copper in sweat at 2.59 µg/L. Another found 652.49 µg/L. That’s roughly a 250-fold gap for the same element, and the likely culprit is what got scraped up alongside the sweat, not biological variation.

So the next time you see a number about how much “toxins” a sauna pulled from someone’s skin, ask one question: did the researchers clean the skin before collecting, and did they filter the sample afterward? If the answer is unclear, the number probably isn’t trustworthy.

Inside the 2022 study: how the research measured the sweat

What makes the 2022 crossover study worth trusting isn’t a laboratory. It’s the attention paid to the mundane details that most “detox” claims skip:

• The test subjects: 12 healthy university students (6 men, 6 women), all moderately active, with an average age around 22. A small group, but a well-controlled one.
• Dietary control: for one week before and throughout the experiment, subjects ate from the same restaurant, with intake monitored to minimize dietary variation.
• Skin preparation: before collection, researchers cleaned the skin thoroughly to avoid whatever was already on it from contaminating the samples.
• The collection method: a homemade sweat collector, a funnel with a glass tube, cleaned with deionized water and covered with tin foil.
• Filtration: each sweat sample was passed through a 0.22-micron filter before analysis, catching skin flakes and cellular debris.
• The analysis: two lab techniques, ICP-AES for nickel, lead, and copper, and the more sensitive ICP-MS for arsenic and mercury, with calibration standards covering the expected sweat concentrations.
• The comparison: a paired t-test, since each participant served as their own baseline. (Source: PMC8998800.)

These details are your real story. They’re what separate a finding you can lean on from a “detox” claim someone made with a spreadsheet and a wellness-adjacent Instagram page.

The clinical significance debate: meaningful detox or negligible amounts?

This is the heart of it: is any of this doing anything for your body, or is it just an expensive thermometer?

Here’s what the skeptic-with-numbers side says. In a body of research (published in, among other places, National Geographic, where the finding was widely reported), respiratory physiologist Pascal Imbeault quantified how much of these pollutants actually leaves through your skin. His number: more than 99% of sweat is water. The pollutants in two liters of sweat, about 4.4 pounds, came out to less than one-tenth of a nanogram.

That’s roughly 0.02% of the daily intake you’d get from your diet. A rounding error.

And here’s the counterweight. A 2023 study on water-filtered infrared-A (wIRA) saunas, 22 participants sweating in a warm sauna, analyzed with ICP-MS, found that infrared sauna sweat contained toxic elements at concentrations exceeding those from conventional exercise. Lead came in at up to 497 times higher concentrations. Mercury at 34.8 times. Arsenic at 18 times.

Both of these things can be true simultaneously. Your sauna sweat can carry relatively high concentrations of heavy metals, and the absolute amounts can still be so small that they don’t amount to meaningful detoxification for your body overall.

The experts’ consensus: you have two much more effective detox organs already, your liver and kidneys. And “sauna for detox” isn’t no-show; there’s a real cardiovascular effect to heat exposure (lower blood pressure, improved heart-rate variability) that doesn’t depend on the detox claim at all. You just have to want the right thing from the heat.

The tradeoff: minerals lost in infrared sauna sweat

Here’s the detail nobody puts on their wellness-cabinet brochure: the same 2023 wIRA study that found lead concentrations in infrared sauna sweat also documented losses of the good stuff.

Calcium, magnesium, zinc, the things you actually need.

If a sauna session is pulling lead, arsenic, and mercury out of your bloodstream, it’s also pulling out the beneficial minerals your body relies on for muscle function, bone health, and keeping your immune system running. One session isn’t a problem. But if you’re doing infrared sauna sessions regularly, a few times a week, for months, that steady mineral loss adds up, and you need a plan to replace what you’re sweating out.

Electrolyte replacement is table stakes for any sauna user. What most people miss is the mineral component. That’s where you need to think beyond the sports drink aisle: are you getting enough magnesium and zinc in your regular diet?

Infrared sauna detox: safety limits and practical takeaways

So: what should you actually do with all this?

Replacing minerals and electrolytes after a session

If you’re doing regular infrared sauna sessions, a reasonable default is to drink water before, sip electrolytes during longer sessions, and after a heavier session, reach for something that includes electrolytes and trace minerals, not just water.

You can take this as a loose direction rather than a strict protocol. But skipping the replacement step when you’re sweating regularly isn’t a great idea.

Infrared vs. traditional sauna for detox

Infrared saunas run cooler than traditional saunas, typically 120-145°F (around 50-65°C) versus a traditional sauna’s 180-200°F (about 85-95°C). Because of that lower temperature, you can stay in longer, which means more total sweating time and potentially more total excretion.

The science is still thin, most infrared sauna research has small sample sizes (20-30 participants). But the direction favors the infrared approach for someone who can tolerate longer sessions: lower temperature, more total sweat time, and a longer window for whatever’s in your sweat to actually come out.

Safety limits

The American College of Sports Medicine recommends keeping sauna sessions to about 10-15 minutes per session if you’re using heat for something like blood-pressure support. That’s a sensible upper bound to work within for a standard session (a longer, cooler session is fine if you’re tolerating it and drinking enough). The main risks are dehydration and overheating, both manageable if you stay hydrated and get out before you feel dizzy. If you have cardiovascular disease or are pregnant, check with a doctor before adding regular sauna use.

The honest bottom line on sauna detox

Using the sauna because you enjoy the heat is good for you. Using it because you’re trying to hit some sort of “detox quota” is a misunderstanding, your liver and kidneys are already doing the heavy lifting, and sauna isn’t the replacement you’re looking for.

But there’s a hidden value in the heat that the “detox” framing misses. Regular sauna use has real, measurable benefits for your cardiovascular system, lower blood pressure, better blood vessel function, and a stress-reduction component that shows up in heart-rate-variability data.

If you want the physiological benefits of heat, use the sauna for that, not to flavor a fantasy about flushing out a life’s worth of accumulated toxins. The numbers don’t support the version where a sauna session replaces a weekend run or a hydration habit.

The sauna does do something for you, you just have to want the right thing from it.

And if you want to actually sweat more heavy metals? A treadmill will do that faster than a sauna will. You’re not going to love the answer. But the sweat doesn’t lie.