Editing Perspiration (section)

== Composition ==
[[File:TranspirationPerspirationCommonsFL.jpg|thumb|alt=Close-up of beads of sweat|Beads of sweat emerging from [[eccrine gland]]s]]

Sweat is mostly [[water]]. A microfluidic model of the eccrine sweat gland provides details on what solutes partition into sweat, their mechanisms of partitioning, and their fluidic transport to the skin surface.<ref name="2015-Sonner">{{Cite journal |last=Sonner |first=Z. |last2=Wilder |first2=E. |last3=Heikenfeld |first3=J. |last4=Kasting |first4=G. |last5=Beyette |first5=F. |last6=Swaile |first6=D. |last7=Sherman |first7=F. |last8=Joyce |first8=J. |last9=Hagen |first9=J. |date=2015-05-01 |title=The microfluidics of the eccrine sweat gland, including biomarker partitioning, transport, and biosensing implications |journal=Biomicrofluidics |volume=9 |issue=3 |pages=031301 |doi=10.1063/1.4921039 |issn=1932-1058 |pmc=4433483 |pmid=26045728}}</ref>
Dissolved in the water are trace amounts of [[minerals]], [[lactic acid]], and [[urea]]. Although the mineral content varies, some measured concentrations are: [[sodium]] ({{nowrap|0.9 gram/litre}}), [[potassium]] ({{nowrap|0.2 g/L}}), [[calcium]] ({{nowrap|0.015 g/L}}), and [[magnesium]] ({{nowrap|0.0013 g/L}}).<ref>{{Cite journal |last=Montain |first=S. J. |last2=Cheuvront |first2=S. N. |last3=Lukaski |first3=H. C. |year=2007 |title=Sweat mineral-element responses during 7 h of exercise-heat stress |journal=International Journal of Sport Nutrition and Exercise Metabolism |volume=17 |issue=6 |pages=574–582 |doi=10.1123/ijsnem.17.6.574 |pmid=18156662 |s2cid=3030692}}</ref>

Relative to the plasma and extracellular fluid, the concentration of Na<sup>+</sup> ions is much lower in sweat (≈40 mM in sweat versus ≈150 mM in plasma and extracellular fluid). Initially, within [[eccrine glands]] sweat has a high concentration of Na<sup>+</sup> ions. In the sweat ducts, the Na<sup>+</sup> ions are re-absorbed into tissue by [[epithelial sodium channels]] (ENaC) that are located on the apical membrane of epithelial cells that form the duct (see Fig. 9 of the reference).<ref name="2017-Hanukoglu" />

Many other [[trace elements]] are also excreted in sweat, again an indication of their concentration is (although measurements can vary fifteenfold) [[zinc]] ({{nowrap|0.4 milligrams/litre}}), [[copper]] ({{nowrap|0.3–0.8 mg/L}}), [[iron]] ({{nowrap|1 mg/L}}), [[chromium]] ({{nowrap|0.1 mg/L}}), [[nickel]] ({{nowrap|0.05 mg/L}}), and [[lead]] ({{nowrap|0.05 mg/L}}).<ref>{{Cite journal |vauthors=Cohn JR, Emmett EA |year=1978 |title=The excretion of traces of metals in human sweat |journal=Annals of Clinical and Laboratory Science |volume=8 |issue=4 |pages=270–5 |pmid=686643}}</ref><ref>{{Cite journal |last=Saraymen |first=Recep |last2=Kılıç |first2=Eser |last3=Yazar |first3=Süleyman |year=2004 |title=Sweat Copper, Zinc, Iron, Magnesium and Chromium Levels in National Wrestler |url=http://mail.inonu.edu.tr/~tipdergi/include/getdoc.php?id=79&article=35&mode=pdf |journal=İnönü Üniversitesi Tıp Fakültesi Dergisi |volume=11 |issue=1 |pages=7–10 |archive-url=https://web.archive.org/web/20110820121750/http://mail.inonu.edu.tr/~tipdergi/include/getdoc.php?id=79&article=35&mode=pdf |archive-date=2011-08-20}}</ref> Probably many other less-abundant trace minerals leave the body through sweating with correspondingly lower concentrations. Some exogenous organic compounds make their way into sweat as exemplified by an unidentified odiferous "maple syrup" scented compound in several of the species in the mushroom genus ''Lactarius''.<ref>Aurora, David "Lactarius fragilis" ''Mushrooms Demystified'' 1986 Ten Speed Press, Berkeley California</ref> In humans, sweat is [[Hypotonicity|hypoosmotic]] relative to [[Blood plasma|plasma]]<ref>{{Cite book |last=Constanzo |first=Linda S. |title=BRS Physiology |edition=6th |page=151}}</ref> (i.e. less [[Concentration|concentrated]]). Sweat is found at moderately acidic to neutral pH levels, typically between 4.5 and 7.0.<ref>{{Cite journal |vauthors=Bandodkar AJ, Hung VW, Jia W, Ramirez GV, Windmiller JR, Martinez AG, Ramirez J, Chan G, Kagan K, Wang J |year=2013 |title=Tattoo-based potentiometric ion-selective sensors for epidermal pH monitoring |journal=Analyst |volume=138 |issue=1 |pages=123–8 |bibcode=2013Ana...138..123B |doi=10.1039/c2an36422k |pmid=23113321}}</ref>

Sweat contains many [[glycoprotein]]s.<ref name=":1">{{Cite journal |last=Robyn A Peterson |last2=Audrey Gueniche |last3=Ségolène Adam de Beaumais |last4=Lionel Breton |last5=Maria Dalko-Csiba |last6=Nicolle H Packer |date=17 November 2015 |title=Sweating the small stuff: Glycoproteins in human sweat and their unexplored potential for microbial adhesion |journal=Glycobiology |volume=26 |issue=3 |pages=218–229 |doi=10.1093/glycob/cwv102 |pmid=26582610 |doi-access=free}}</ref>