Intraday Variations in Skin Water Parameters

Introduction: Three interrelated skin water assessments include stratum corneum hydration (SCH) via electrical measurements, skin water using tissue dielectric constant (TDC) measurements, and transepidermal water loss (TEWL). These are differentially used for skin physiology research, clinical assessments of dermatological conditions and to assess skin water in diabetes and lymphedema. Often volar forearm skin is used for assessments done at various times of day (TOD). The present goal was to assess the extent of intraday variability in SCH, TDC, and TEWL. Methods: Twelve medical students self-measured SCH, TDC, and TEWL on their forearm every 2 h from 08:00 to 24:00 h on 2 consecutive days. All participants were well trained and pre-certified in all procedures. Tests for parameter differences among TOD were via the nonparametric Friedman test. Results: No significant differences in SCH or TEWL were found among TOD over the 16-h interval for either day or combined. Contrastingly, TDC decreased slightly but significantly from morning through evening. There was no evidence of a diurnal pattern. Interestingly, a significant nonlinear relationship between TEWL and SCH was detected. Conclusion: Findings indicate only minor intraday variations with TOD trend except for TDC which decreases slightly from morning through evening. The clinical relevance relates to the confidence now gained associated with the parameter estimates when measured at different TOD during normal clinic hours or beyond. This should help in estimating the potential importance of small differences if measured at a different TOD. From a physiological viewpoint, the findings uncover and describe an interesting nonlinear relationship between TEWL and SCH which may serve to propel further investigations that might better characterize this process.