Effects of Skin Hydration on Electrodermal Activity

Abstract: Electrodermal activity (EDA) is a general term for the electrical characteristics of the skin associated with sympathetic nervous system activity. It is shown that various factors can impact EDA measurements. Skin hydration may be one of the possible factors that could influence EDA measurements. This study aimed to examine the effects of skin hydration on tonic and phasic EDA measurements by using a new technique that could record all EDA parameters: skin conductance (SC), skin potential (SP), and skin susceptance (SS), at the same skin sites. 60 (30 male and 30 female) healthy volunteers participated in the study through two different experimental conditions (normal and hydration). They were subjected to four external stimuli: math, breathing, image, and sound to elicit EDA responses. Skin hydration was produced by applying 0.2 g of 0.5% KCI in a 2% agar jelly medium to the selected skin sites for electrode placement. Tonic and phasic EDA components were significantly ( p < 0.01, Wilcoxon signed-rank test) influenced by skin moistening. Moreover, EDA levels and amplitudes significantly increased, whereas time-dependent scores were not changed following skin hydration. It is concluded that tonic (level) and phasic (amplitude) EDA components are strongly influenced by skin hydration. This should be considered in the applications of EDA devices, and any factor (other than psychological sweating) that moistens skin should be avoided.