Leaching from the stratum corneum does not explain the previously reported elevated potassium ion concentration in sweat

BACKGROUND The purpose of this study was to determine if K+ is leached from the stratum corneum when sweat is present on the skin's surface. The results will help address whether sweat [K+] previously reported in the literature are artifactually elevated as a result of K+ leaching. METHODS Twelve (six female, six male) healthy volunteers participated in this study. After thorough skin cleansing and preparation with isopropyl alcohol and high-performance liquid chromatography-grade distilled water, three sites were chosen and a 50 μL drop of artificial sweat was pipetted directly onto the skin. The artificial sweat had a [K+] of 4 mEq·L-1, an osmolality of 120 mosm·L-1, and a pH of 6.0. Immediately following, a clear plastic cover slip (~6 cm2) with a shallow 0.8 cm2 convex impression in the center was applied over each drop, preventing evaporation. Each sample was allowed to sit on the forearm, under the plastic cover slip, for 10 min. RESULTS The mean (±SD) [K+] in 'artificial' sweat not exposed to the skin was measured to be 4.2±0.4 mEq·L-1. After 10 min of exposure to the stratum corneum of the forearm, the artificial sweat had a mean (±SD) [K+] of 3.9±0.3 mEq·L-1. There was no significant difference (p>0.05) in the [K+] between the control artificial sweat and the samples collected after 10 min of exposure to forearm skin. CONCLUSIONS These results do not support the hypothesis that significant K+ leaching from the stratum corneum into standing sweat is the cause for the previously reported elevated sweat [K+].