Transepidermal water loss and stratum corneum hydration in forearm versus hand palm

Background: Skin measurements of transepidermal water loss (TEWL) and stratum corneum hydration (SCH) reflect different aspects of skin physiology. Since epidermal water loss depends on epidermal-to-air water vapor gradients, a possible quantitative relationship between TEWL and SCH may exist. This investigation's purpose was to test the possible TEWL-SCH relationship. Materials and Methods: SCH and TEWL were measured noninvasively on forearm and palmer thenar eminence (hand) in 40 young adults (20 males) along with total body fat percentage (FAT) via bioimpedance. Results: A significant positive nonlinear correlation (p < 0.001) was detected between SCH and TEWL in hands of the male cohort that occurred when SCH exceeded a threshold level. This threshold level was not exceeded in male or female forearms and forearms did not display a SCH-TEWL correlation. There was a weak inverse dependence of TEWL on FAT on both forearm and hand (p < 0.05), but no SCH-FAT relationship was observed. TEWL values on the forearm and hand were moderately correlated with each other (p = 0.002) but SCH values were not. Conclusion: The findings clarify the relationship between forearm and palmer hydration and TEWL values, and their relationship to total body fat percentages in young healthy adults. The significant correlation between palmer stratum corneum hydration and palmer TEWL that was discovered in the male but not the female cohort suggests a threshold hydration level for which TEWL depends both on skin barrier function and stratum corneum hydration. This implies that conditions with increased SCH may in part account for elevated TEWL values.