“Infrared sauna sweat is 20% toxins, where a normal sauna's is only 3%.”

The research found this

We could not find a scientific source for these percentages. The earliest version we traced is a 2002 page from an infrared sauna seller, which credited one study by American researchers and named none. The numbers were still traveling in June 2021, when WMC Action News 5 published a syndicated "Best Life" segment from Ivanhoe Broadcast News that credited them to unnamed studies. A dental clinic's blog repeated them that October and cited only the news page.

Sweat is mostly water. A 2019 review of sweat physiology gives typical concentrations of 10–90 mmol/L each for sodium and chloride, 5–40 mmol/L for lactate, 4–12 mmol/L for urea and 2–8 mmol/L for potassium.1Source 1 · ReviewPhysiology of sweat gland function: The roles of sweating and sweat composition in human healthBaker LB. Temperature, 2019.Read the paper ↗PubMed ↗ Added up at the top of each range, those come to about 10 g per liter, which is roughly 1% of sweat by mass. Lead runs at about 4–12 µg/L, which is around a millionth of a percent.

The one study that compared sweat from different sauna types found no difference in BPA. In the 20-person BUS study on BPA, 10 people collected sweat in an infrared sauna and 10 in a steam sauna or during exercise, and sweat BPA did not differ by method.2Source 2 · Cross-sectional studyHuman Excretion of Bisphenol A: Blood, Urine, and Sweat (BUS) StudyGenuis SJ, Beesoon S, Birkholz D, et al.. Journal of Environmental and Public Health, 2012.Read the paper ↗PubMed ↗

Infrared cabins also produced less sweat in the only head-to-head test. Twenty adults lost 0.39 kg over 45 minutes of far-infrared heat and 0.66 kg over three 10-minute rounds in a traditional sauna.3Source 3 · Crossover trialComparison of thermoregulatory, cardiovascular, and immune responses to different passive heat therapy modalitiesAtencio JK, Reed EL, Wiedenfeld Needham K, et al.. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2025.Read the paper ↗PubMed ↗ That difference did not reach statistical significance (P = 0.16).

The highest metal readings come from a water-filtered infrared-A capsule at a Korean hospital. Sweat drained from all body parts of 22 visitors, 21 of whom had conditions such as diabetes or cancer, held mercury at 29.9 µg/L.4Source 4 · Case seriesEffect of water filtration infrared-A (wIRA) sauna on inorganic ions excreted through sweat from the human bodyCho KH, Jung SH, Choi MS, et al.. Environmental Science and Pollution Research, 2023.Read the paper ↗PubMed ↗ A controlled study measured 0.2 µg/L in sweat from a sauna cabinet.5Source 5 · Crossover trialExcretion of Ni, Pb, Cu, As, and Hg in Sweat under Two Sweating ConditionsKuan WH, Chen YL, Liu CL. International Journal of Environmental Research and Public Health, 2022.Read the paper ↗PubMed ↗ The capsule study had no comparison group of its own.