REF-1374 · Sears, Kerr & Bray, 2012 · Journal of Environmental and Public Health · Paper · PubMed · Free full text

Can I sweat out heavy metals in a sauna or on a hard ride?

They appear in sweat, highest in exposed workers, by poorly validated methods; the authors favour sweating, but no trial here tested a health benefit. Weak evidence (B-).

Main caveat: No appraisal or pooling. Studies of any design and any collection method were included without a risk-of-bias assessment.
limited, mixed evidenceMeasured on non-athletes

Sears, Kerr and Bray set out to collect every report of arsenic, cadmium, lead or mercury in human sweat, because these elements have no physiological benefit and sweating has long been regarded as cleansing and low-risk.

From 122 records, 24 reports of 22 or 23 studies were included (two from one institution may have reported a subset twice); one German report was used from its extended abstract and one Russian report from the conclusion of its English abstract. Populations, sweat collection methods and concentrations varied widely.

In people with higher exposure or body burden, sweat generally exceeded plasma or urine concentrations, and daily dermal excretion could match or surpass urinary excretion: arsenic excretion through the skin was severalfold higher in arsenic-exposed people than in unexposed controls; cadmium was more concentrated in sweat than in plasma; a third to a half of sweat lead was bound to high-molecular-weight molecules in two men; and in one case report mercury levels in sweat normalised over months of daily sweating after chelation.

The authors' discussion states its own limits: most of the research was over 20 years old, collection methods varied widely, sweat concentrations "are not well validated" and varied with body site, collection method and day, sweat carries metals from the skin as well as from plasma (lead absorbed into workers' skin was not always removed by cleaning), and appropriately sized trials are needed.

Nonetheless they conclude that sweating "deserves consideration" for toxic element detoxification and that physicians could consider recommending sweating, by exercise or sauna, as a low-risk, potentially beneficial treatment. Our reading: this is the opposing systematic review that PHYS-30 names against "sweat's minor part in clearing toxins".

It shows that the four metals are measurable in sweat and sometimes concentrated there in heavily exposed people; it does not show a meaningful share of body burden leaving by sweat in ordinary people, or any health benefit.

Its key data come from collection methods that Baker 2019 (REF-1353) judges prone to skin-surface contamination — the Genuis BUS study and the arm-bag and skin-arsenic studies cited here are among those Baker discusses.

Protocol

Design: systematic review; no meta-analysis, no risk-of-bias or quality appraisal.
Search: Medline, Embase, Toxline, Biosis and AMED, no date or language limit, to 22 March 2011; keyword lists for all compounds of the four elements from the Chemical Rubber Company Handbook; reference lists, key authors, related articles and grey literature.
Screening: titles and abstracts by one investigator; inclusion screening and data extraction independently by two investigators. All studies with quantitative human data on the four elements in sweat were included regardless of design, sweat collection or chemical analysis.
Sample: n = 24 reports (22 or 23 studies) from 122 records; 50 full texts screened, two non-English reports used from abstracts.
Sweat induction and collection in the included studies: sauna, exercise or pilocarpine iontophoresis; arm bags, whole-body wash-down, gauze pads on a T-shirt, membrane filters, sweat collected into bottles, rubber waders.
Funding and interests (as printed): the scoping review from which this work derives was supported by a grant from the Canadian Institutes of Health Research and the Social Sciences and Humanities Research Council of Canada; the authors declare no conflicts of interest.The review's reference list opens with the Institute for Functional Medicine's textbook, and the first author co-wrote a 2012 paper on environmental determinants of chronic disease and detoxification with S. J. Genuis (reference 2), whose BUS study is a main data source here (reference 3).

Key Results

ElementStudiesWhat the review reports
Arsenic2skin excretion severalfold higher in arsenic-exposed groups than in unexposed controls (Bangladesh); in 20 Canadians, arsenic 1.5-fold (men) to 3-fold (women) higher in sweat than plasma but lower than in urine; maximum sweat arsenic 22 μg/L
Cadmium6sweat concentrations from <0.5-10 μg/L to 0.36-35.8 μg/L; total daily excretion greater in sweat than urine in two studies; sweat may be an important route when exposure is high
Lead1136% and 50% of sweat lead bound to molecules >30,000 in two men; higher sweat lead in exposed workers; sweat lead up to 283 μg/L in people without occupational exposure and up to 17,700 μg/L in workers, where lead absorbed in the skin may not have been removed by cleaning; in two people who ingested lead, sweat lead did not rise significantly
Mercury4 in the tablesweat-to-urine ratios from <0.1 to >5 with no correlation in two volunteers; highest sweat mercury 1.5 and 1.4 μg/L in two studies; in three exposed workers 1.5 h of sweat held 120-350 ng of mercury against 160-190 ng in 16 h of urine (one small study); one poisoned worker's sweat mercury normalised over months of sweating after chelation
Overall (authors)24 reportsthe four elements "may be excreted in appreciable quantities through the skin", at rates reported to match or exceed 24-h urinary excretion

What the authors say limits the evidence (their discussion): most research over 20 years old; collection methods varied widely; sweat concentrations measured in research settings not well validated, varying with body site, collection method and day; sweat metals partly from the skin, especially in exposed workers; variability far greater than analytical error; robust, appropriately sized trials needed.

Numbers that do not add up: in the review's tables, the Genuis study's sweat arsenic is given as "mean: 3.1 (range 3.7–22)" and its plasma lead as "mean 0.12 (0.39–1.7)" — means below their own ranges. The abstract says that in an interventional study lead "levels were higher with endurance compared with intensive exercise"; the table shows that this study (read from a German extended abstract) measured a fall in blood lead with rowing (from 430 to 370), not sweat lead.

Mechanisms

Measured (in included studies): the four elements in sweat at concentrations that, in heavily exposed people, can exceed plasma; sweat lead partly bound to large molecules; lead applied to one arm raised sweat lead from the other arm about tenfold, back to baseline after about 2-4 days (absorption through the skin).
Authors' interpretation: sweat is an excretory route for toxic metals, arising mainly from plasma with a contribution from metals absorbed into the skin; sweating could be used therapeutically, alone or with chelators, nutrients or sauna.
Inference: a high concentration in a small volume of surface sweat is not a large amount removed from the body, and metal found on the skin may have come from the skin; the review does not estimate body-burden change from sweating in anyone without heavy exposure, and its clinical recommendation rests on case reports and clinical experience.
Cross-check ([REF-1353]): Baker 2019 argues that contamination-prone collection explains high toxicant readings in sweat, that heavy metals leave the body mainly in faeces, and that direct evidence for sweating as detoxification is lacking.

Practical Application

Can I sweat out heavy metals in a sauna or on a hard ride? They appear in sweat, highest in exposed workers, by poorly validated methods; the authors favour sweating, but no trial here tested a health benefit. Weak evidence (B-).
What it is good for as a source: naming the opposing systematic review in its own words — the metals are measurable in sweat and sometimes concentrated there in exposed people, and the authors think sweating "deserves consideration" — together with the limits the authors themselves state.
What it does not show: that sweating lowers body burden in ordinary people, that it improves any health outcome, or that the measured concentrations are free of skin contamination; its included data are mostly old, small and unappraised.
How a principle should cite it: "a 2012 systematic review held sweating worth considering for toxic metals (Sears 2012), on collection methods that REF-1353 questions; it measured no health outcome".
What it means for training: Not from this paper; the base's own practice: use heat for acclimation, not detox (SYNTH-04), replace the fluid it costs (SYNTH-68), and say "the evidence does not support sweating as a way to detoxify" (REF-1353).

Limitations

No appraisal or pooling. Studies of any design and any collection method were included without a risk-of-bias assessment; titles and abstracts were screened by one investigator.
Old, small, heterogeneous evidence, by the authors' own account; two reports were used from abstracts only, and two lead reports may overlap.
Contamination. Sweat metals partly originate from the skin (stated by the authors for lead); the main multi-element data come from a study whose collection Baker 2019 describes as self-collected and scraped from the skin (REF-1353), while this review describes it as sweat "collected directly into bottle".
No health outcome. The detox recommendation rests on case reports, historical practice and clinical experience, not on trials.
Context of the authors: a functional-medicine framing (first reference) and a co-author link to the Genuis group, whose data are central; no conflicts declared, public research funding.
How this entry was checked and changed
Why this level

the search is systematic, but the evidence it gathers is B-design or below (small measurement studies, two dosing experiments, case reports, two reports read only from abstracts) with high risk of bias from unvalidated, contamination-prone sweat collection, and the outcome is a concentration in sweat, not any health effect; the "deserves consideration" conclusion goes beyond what the included data can show

Full text (checked 2026-10-28)
Medline, Embase, Toxline, Biosis, and AMED were searched to March 22, 2011; of 122 bibliographic records identified, twenty-four reports of 22 or 23 trials or studies were included in evidence synthesis (full text)
Cadmium concentrations in sweat ranged from <0.5–10 μg/L to 0.36–35.8 μg/L; in two males, 36% and 50% of sweat lead was of molecular weight > 30,000 (full text)
Sweat lead levels up to 283 μg/L have been observed in nonoccupationally exposed subjects and up to 17,700 μg/L in workers, where lead in sweat may partially originate from material absorbed within the skin that was not removed by pretest cleaning protocols (full text)
Most of the research identified was over 20 years old, and collection methods varied widely; sweat concentrations measured in research settings are not well validated (full text)
Sweating deserves consideration for toxic element detoxification; research including appropriately sized trials is needed to establish safe, effective therapeutic protocols (full text)
Supported by a grant from the Canadian Institutes of Health Research and the Social Sciences and Humanities Research Council of Canada; the authors declare no conflicts of interests (full text)