the sauna is one of the oldest recovery tools on the planet. and for a lot of people, detoxification is a big part of why they use it. the logic makes sense: raise your core temperature, open the pores, sweat out what your body has been holding onto.
but here's the part most people miss. if you're not paying attention to a few key details, you might be re-introducing the very things you're trying to eliminate, mid-session, while your pores are wide open.
this isn't fear-mongering. there's real research behind it. and the fixes are simple.
what actually comes out in sweat
before getting into what can go wrong, it's worth understanding what's actually leaving your body during a sauna session.
sweat is roughly 99% water. but the remaining 1% is where things get interesting. a systematic review published in the Journal of Environmental and Public Health (Sears et al., 2012) analyzed 24 studies on the excretion of arsenic, cadmium, lead, and mercury in sweat. the findings were significant: in individuals with higher exposure or body burden, sweat concentrations of these metals generally exceeded those found in blood plasma or urine, and dermal excretion could match or surpass urinary daily output. the researchers concluded that sweating deserves consideration for toxic element detoxification.
the foundational study behind much of this work is the Blood, Urine, and Sweat (BUS) Study (Genuis et al., 2011), published in the Archives of Environmental Contamination and Toxicology. the study monitored toxic element levels across all three body fluids in 20 participants and found that some toxic elements were preferentially concentrated in sweat relative to blood. among the notable findings: some participants showed detectable toxicant levels in sweat but not in blood or urine, suggesting sweat may access tissue-level stores that the kidneys and liver aren't efficiently clearing.
a separate study by the same research group found BPA (bisphenol A) in the sweat of 16 out of 20 participants (Genuis et al., 2012, Journal of Environmental and Public Health), including individuals whose blood and urine samples showed no detectable BPA at all. that's significant because it suggests sweat may be reaching stores of certain chemicals that the kidneys and liver aren't efficiently clearing on their own.
similar findings have been documented for phthalates (chemicals used to make plastics flexible). a companion BUS study on phthalate excretion (Genuis et al., 2012, The Scientific World Journal) found sweat concentrations roughly double those found in urine, with some parent compounds (DEHP) appearing in sweat but not in blood serum.
does that mean the sauna is a miracle detox machine? no. your liver and kidneys are still doing the vast majority of the work. but the research does support sweating as a meaningful complementary pathway, especially for certain fat-soluble compounds that accumulate in tissue over time. infrared saunas, which raise core temperature through direct tissue penetration rather than heating the surrounding air, may be particularly effective at mobilizing these deeper stores.
what you wear matters more than you think
here's the first place most people go wrong: clothing.
synthetic fabrics like polyester, nylon, and spandex are made from plastic-derived materials. under normal conditions, they shed microfibers. but in a hot, humid environment where your skin is sweating and your pores are dilated, the equation changes.
a 2024 study from the University of Birmingham (Abafe et al., published in Environment International) provided the first experimental evidence that toxic chemicals present as additives in microplastics can leach into human sweat and then be absorbed through the skin into the bloodstream. using 3D human skin equivalent models, the study found that sweatier skin absorbed higher levels of flame-retardant chemicals (polybrominated diphenyl ethers, or PBDEs) from microplastic particles, with up to 8% of the chemical load crossing the skin barrier. the absorbed fraction was strongly correlated with water solubility, and sweaty skin showed significantly higher bioavailability than dry skin.
a prior study by the same team (2023, published in Environmental Science and Technology) had already demonstrated that human sweat can leach flame-retardant chemicals out of microplastic particles in the first place, identifying polyethylene microplastics as the worst offenders for bioaccessibility.
in practical terms: sitting in a sauna wearing polyester or nylon means you're in a high-heat, high-sweat environment with plastic-based fabric pressed against your skin. your pores are open. your skin is wet. the conditions for dermal absorption are about as favorable as they get.
the fix is straightforward. wear cotton or organic cotton in the sauna. natural fibers don't shed microplastics and don't carry the same chemical load. if your sauna is private, no clothing at all is ideal. a cotton towel underneath you works the same way.
this is also worth considering when choosing a sauna itself. the materials inside the enclosure matter just as much as what you're wearing. look for saunas built with natural wood interiors and non-toxic adhesives. at high temperatures, adhesives, finishes, and sealants release volatile organic compounds (VOCs) at higher rates, meaning you could be breathing in the same types of compounds you're trying to sweat out. Coldture's indoor saunas, for example, use canadian hemlock and red cedar interiors with non-toxic paint and biodegradable adhesives specifically because what you breathe at 65-90°C matters.
don't sit in your sweat
this one sounds obvious once you hear it, but most people don't think about it.
when you sweat, your body is pushing waste products to the surface. those compounds sit on your skin until they're removed. in a sauna, the heat keeps your pores open, which means anything sitting on the surface of your skin has an easier path back in.
the mechanism is supported by the same dermal absorption research. the Birmingham study confirmed that hydrated (sweaty) skin absorbs chemicals at significantly higher rates than dry skin. if toxicant-containing sweat is pooling on your skin in a hot environment, the conditions for reabsorption are present.
the fix: wipe your skin during the session. a simple cotton towel or cloth is all you need. periodically wiping your face, arms, chest, and legs removes the surface layer of sweat and the trace compounds it carries. some people use a gentle scraping tool for the same purpose.
think of it less as "cleaning up" and more as keeping the exit lane clear. your body is trying to push things out. don't let them pool and get reabsorbed through the same open pores.
this is one reason many traditional sauna cultures, from finnish to korean to russian, include some form of scrubbing, brushing, or rinsing as part of the ritual. the principle is the same: keep the surface clean so the body can keep releasing.
go in with a clean face
your pores dilate significantly in the heat. this is part of what makes sauna sessions beneficial for skin health: increased blood flow, deeper sweating, and a natural flush of oil, debris, and dead skin cells.
but that same dilation works in both directions. when your pores are wide open, your skin becomes more absorbent. the dermal absorption literature consistently shows that damaged, hydrated, or occluded skin has a significantly higher absorption rate for chemicals than dry, intact skin. sweating skin in a hot environment checks multiple boxes for enhanced permeability.
if you go into the sauna wearing makeup, sunscreen, or skincare products with synthetic ingredients, those compounds now have easier access to deeper layers of your skin and, potentially, your bloodstream. the very heat that's supposed to help you detox is also increasing the bioavailability of whatever's sitting on your face.
the rule: go in bare-faced. remove all makeup, lotions, and synthetic skincare products before your session. wash your face with a gentle, natural cleanser.
there's a useful flip side to this, though. because your skin is more absorbent in the sauna, natural oils can penetrate more effectively. olive oil in your hair, castor oil on your eyebrows or lashes, or a simple natural moisturizer applied after your session can take advantage of the increased absorption working in your favor. if what's going in is clean, the enhanced absorption becomes a benefit, not a liability.
the sauna itself matters
most of the conversation around sauna detox focuses on behavior: what to wear, what to put on your skin, how long to stay. but the environment itself plays a role too.
heat type. traditional finnish saunas heat the air around you using a stone heater, producing high-temperature dry heat (typically 80-110°C). infrared saunas use far-infrared panels to heat the body directly at lower air temperatures (typically 45-65°C). both induce sweating, but through different mechanisms.
for people whose primary goal is supporting detoxification, infrared may offer an advantage. because infrared wavelengths penetrate 1-2 inches into tissue, they raise core temperature more gradually and may help mobilize fat-soluble toxins stored deeper in the body. a 2023 study found that sweat produced during infrared sauna sessions contained higher concentrations of certain toxic metals compared to sweat from conventional exercise or traditional saunas.
that said, traditional saunas have their own strengths. higher air temperatures produce a more intense cardiovascular response and are associated with well-documented benefits for heart health, blood pressure, and overall circulation.
if you're choosing between the two, don't overthink it. both are effective. the best option is the one you'll use consistently. and if you want both, the Coldture hybrid sauna runs a dedicated 6 kW heater and 2,920W of independent ultra-low EMF infrared panels on the same system, so you can switch between modes depending on the session.
materials. this gets less attention than it should. at sauna temperatures, adhesives, finishes, and sealants release volatile organic compounds (VOCs) at higher rates. if your sauna is built with chemical-based glues or synthetic materials, you may be inhaling low levels of the same types of compounds your body is trying to eliminate through sweat.
look for saunas that specify non-toxic adhesives and natural wood construction. if the manufacturer doesn't mention it, that's usually because they haven't addressed it. Coldture's infrared saunas, including the pod and corner pod, are built with non-toxic paint and biodegradable glue throughout, specifically because what you breathe at these temperatures matters as much as what you sweat out.
putting it together: a cleaner sauna protocol
most of the conversation around sauna detox focuses on behavior: what to wear, what to put on your skin, how long to stay. but the environment itself plays a role too.
heat type. traditional finnish saunas heat the air around you using a stone heater, producing high-temperature dry heat (typically 80-110°C). infrared saunas use far-infrared panels to heat the body directly at lower air temperatures (typically 45-65°C). both induce sweating, but through different mechanisms.
for people whose primary goal is supporting detoxification, infrared may offer an advantage. because infrared wavelengths penetrate 1-2 inches into tissue, they raise core temperature more gradually and may help mobilize fat-soluble toxins stored deeper in the body. a 2022 study published in the International Journal of Environmental Research and Public Health compared heavy metal excretion under two sweating conditions and confirmed measurable nickel, lead, copper, arsenic, and mercury in sweat from both exercise and sauna. a separate 2023 study found that sweat produced during infrared sauna sessions contained higher concentrations of certain toxic metals compared to sweat from conventional exercise or traditional saunas.
that said, traditional saunas have their own strengths. higher air temperatures produce a more intense cardiovascular response and are associated with well-documented benefits for heart health, blood pressure, and overall circulation.
if you're choosing between the two, don't overthink it. both are effective. the best option is the one you'll use consistently. and if you want both, the Coldture hybrid sauna runs a dedicated 6 kW heater and 2,920W of independent ultra-low EMF infrared panels on the same system, so you can switch between modes depending on the session.
materials. this gets less attention than it should. at sauna temperatures, adhesives, finishes, and sealants release volatile organic compounds (VOCs) at higher rates. if your sauna is built with chemical-based glues or synthetic materials, you may be inhaling low levels of the same types of compounds your body is trying to eliminate through sweat.
look for saunas that specify non-toxic adhesives and natural wood construction. if the manufacturer doesn't mention it, that's usually because they haven't addressed it. Coldture's infrared saunas, including the pod and corner pod, are built with non-toxic paint and biodegradable glue throughout, specifically because what you breathe at these temperatures matters as much as what you sweat out.
putting it together: a cleaner sauna protocol
none of this is complicated. the adjustments are small, and once they become habit, they add up.
before your session: remove all makeup, lotions, and synthetic skincare. wash your face and body with a gentle, natural cleanser. change into cotton or organic cotton clothing, or go without. have a clean cotton towel ready to sit on and one to wipe with.
during your session: wipe your skin periodically. face, arms, chest, legs. don't let sweat pool on the surface. if you want to take advantage of the increased absorption, apply natural oils (olive oil for hair, castor oil for brows) before or during the session.
after your session: shower. this is non-negotiable. rinse off everything that your body pushed to the surface. cool water is ideal because it helps close your pores after they've been open throughout the session. follow with a natural moisturizer if your skin tends to dry out.
hydration: you're losing significant fluid volume. drink water before, during, and after. mineral-rich water or adding electrolytes is smart, especially for longer sessions.
the bigger picture
the sauna isn't just about detox. the cardiovascular benefits are well-documented. a comprehensive review published in Mayo Clinic Proceedings (Laukkanen et al., 2018) found that regular sauna bathing is associated with reduced risk of cardiovascular disease, improved blood pressure, enhanced vascular function, and reduction in the risk of neurocognitive diseases. the researchers noted that sauna bathing improves endothelium-dependent vasodilation, reduces arterial stiffness, and modulates the autonomic nervous system toward parasympathetic dominance. a landmark 20-year prospective study by the same group (the Finnish Kuopio Ischemic Heart Disease Risk Factor Study, published in JAMA Internal Medicine, 2015) found that men who used the sauna 4-7 times per week had a 50% reduction in cardiovascular death and a 63% reduction in sudden cardiac death compared to those who used it once per week. those benefits hold whether you're using traditional or infrared heat.
add in the stress reduction, the sleep improvement, the skin benefits, and the simple act of building a daily ritual that forces you to stop and do nothing for 15-20 minutes, and the sauna becomes one of the highest-value recovery tools available.
the detox angle is real but nuanced. your liver and kidneys are doing most of the heavy lifting. sweating supports the process, particularly for certain persistent environmental chemicals that accumulate in fat tissue. and the small behavioral adjustments outlined above, what you wear, what's on your skin, how you manage your sweat, can make the difference between a session that works with your body and one that quietly works against it.
if you're building an outdoor setup, Coldture's outdoor sauna pro and outdoor sauna xtreme are both canadian-built with western red cedar interiors and hurricane-rated construction for permanent year-round installation. no seasonal teardown required.
explore Coldture's full sauna lineup: indoor infrared, hybrid, and outdoor traditional models, all built with natural wood interiors, non-toxic materials, and the engineering to support daily use for years. shop saunas.
sources
- Sears ME, Kerr KJ, Bray RI. "Arsenic, Cadmium, Lead, and Mercury in Sweat: A Systematic Review." Journal of Environmental and Public Health, 2012.
- Genuis SJ, Birkholz D, Rodushkin I, Beesoon S. "Blood, Urine, and Sweat (BUS) Study: Monitoring and Elimination of Bioaccumulated Toxic Elements." Archives of Environmental Contamination and Toxicology, 2011.
- Genuis SJ, Beesoon S, Birkholz D, Lobo RA. "Human Excretion of Bisphenol A: Blood, Urine, and Sweat (BUS) Study." Journal of Environmental and Public Health, 2012.
- Genuis SJ, Beesoon S, Lobo RA, Birkholz D. "Human Elimination of Phthalate Compounds: Blood, Urine, and Sweat (BUS) Study." The Scientific World Journal, 2012.
- Abafe OA, Harrad S, Abdallah MA. "Assessment of Human Dermal Absorption of Flame Retardant Additives in Polyethylene and Polypropylene Microplastics Using 3D Human Skin Equivalent Models." Environment International, 2024.
- Lao JY, Chua YJK, et al. "Excretion of Ni, Pb, Cu, As, and Hg in Sweat under Two Sweating Conditions." International Journal of Environmental Research and Public Health, 2022.
- Laukkanen JA, Laukkanen T, Kunutsor SK. "Cardiovascular and Other Health Benefits of Sauna Bathing: A Review of the Evidence." Mayo Clinic Proceedings, 2018.
- Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. "Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events." JAMA Internal Medicine, 2015.
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