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Table 1 Summary of select sweat constituents listed from highest to lowest concentrations

From: Physiological mechanisms determining eccrine sweat composition

 SymbolSweat (mmol/L)Blooda (mmol/L)Molecular weight (Da)Other characteristicsMechanism(s) of secretion in secretory coilMechanism(s) of ductal reabsorption
SodiumNa10–90135–14523Ion ( +)Paracellular transportEpithelial Na channels and Na–K-ATPase
ChlorideCl10–9098–10735Ion (−)Na–K–2Cl cotransport modelCFTR
LactateC3H5O35–400.5–2590Polar moleculeByproduct of sweat gland metabolism; transported out of clear cells via MCT proteins?NA
UreaCH4N2O4–122.5–7.160Polar moleculePassive diffusion via transcellular or paracellular transport? Transcellular transport via UT-1?NA
PotassiumK2–83.6–5.239Ion (+)Na–K–2Cl cotransport modelNA
AmmoniaNH31–80.01–0.0317Polar moleculePassive diffusion via transcellular or paracellular transport?NA
EthanolC2H5OH0–70–746Polar molecule, with both hydrophilic and hydrophobic propertiesPassive diffusion via transcellular or paracellular transportNA
BicarbonateHCO30.5–522–2961Polar moleculeHCO3/Cl channels (Best2) in the dark cells and HCO3/Cl exchanger in luminal cell?CFTR combined with H secretion and HCO3/Cl exchanger in luminal cell?
CalciumCa0.2–22.2–2.740Ionized (++) and boundParacellular transport?NA
MagnesiumMg0.02–0.400.7–0.9524Ionized (++) and boundParacellular transport?NA
GlucoseC6H12O60.01–0.203.9–7.8180Polar moleculeParacellular transport; Transcellular transport via GLUT2, SGLT3, SGLT4?NA
Amino AcidsR–CH(NH2) –COOH ≤ 13 × 10–3 each ≤ 6.5 × 10–3 each75–204 eachPolar and nonpolarLeaching of natural moisturizing factors from the skinNA
IronFe0.1–30 × 10–36–27 × 10–356Mostly protein boundParacellular transport or transcellular carrier-mediated system?NA
CopperCu0.5–20 × 10–312–23 × 10–364Mostly protein boundParacellular transport or transcellular carrier-mediated system?NA
ZincZn0.1–20 × 10–310–17 × 10–365Mostly protein boundParacellular transport or transcellular carrier-mediated system?NA
Ascorbic AcidC6H8O61–10 × 10−320–110 × 10–3176Polar moleculeParacellular transport?NA
ThiamineC12H17N4OS+ ≤ 13 × 10–57–18 × 10–5266Polar moleculeParacellular transport?NA
CortisolC21H30O50.06–0.70 × 10–55–70 × 10–5362Nonpolar molecule; mostly protein boundPassive diffusion of unbound fraction onlyNA
Cytokines0.07–1.0 × 10–9 each ≤ 600 × 10–9 each ~ 16 to 25 kDa eachPolar moleculesProduction by eccrine glandsNA
  1. Supporting references for sweat concentrations are in Supplemental Table 1
  2. aBlood values are normal reference ranges for adults obtained from Mayo Clinic Laboratories Test Catalog (https://www.mayocliniclabs.com/test-catalog/index.html). Specimen type varies among the constituents—reported ranges apply to serum (cortisol, urea, iron, calcium, sodium, potassium, chloride, bicarbonate, magnesium, ethanol, copper, zinc), plasma (cytokines, ammonia, lactate, amino acids, ascorbic acid), serum or plasma (glucose) or whole blood (thiamine). Range for plasma lactate concentration includes rest (0.5–2.2 mmol/L) and exercise (up to ~ 15 to 25 mmol/L in response to “all-out” maximal exertion) (Goodwin et al. 2007). NA, not applicable or no data available