Evaluating the Impact of hydration on electrodermal activity: A Comparison between AC bioimpedance and DC skin potential metrics

Abstract

This study evaluates the comparative sensitivity and stability of tonic and phasic electrodermal activity (EDA) parameters, specifically skin conductance (SC), susceptance (SS), and potential (SP), following a localized moisturizer intervention. Utilizing a single-group pretest-posttest design (N = 55), the research demonstrates that AC bioimpedance-based metrics (SC and SS) exhibit distinct response dynamics compared to conventional DC-based measures. Tonic-level analysis revealed that SCL and SSL produced nearly identical relative percentage increases (52.6%) compared to SPL (34.46%). While SCL provided the largest absolute change, SSL emerged as the most statistically stable indicator across the cohort, characterized by a highly uniform signal-to-noise ratio (d = 1.23). Phasic analysis revealed that Skin Susceptance Responses (ΔSSRs) demonstrated a highly pronounced downward shift following the intervention, characterized by a −70.2% change from baseline. This negative shift was significantly divergent from the potential response (p < 0.001, d = −0.55), highlighting a distinct directional sensitivity for ΔSSRs under these experimental conditions. These findings suggest that AC-based EDA parameters are highly responsive to the resistive and capacitive shifts within the stratum corneum interface. The results suggest that for applications evaluating localized skin surface changes, a multimodal approach incorporating AC bioimpedance-based metrics may provide a highly responsive framework for detecting acute alterations at the electrode-skin interface compared with traditional potential-based measurements.