Passive sustainable hydration of the stratum corneum following surfactant challenge

Surfactants exhibit a protein-denaturating potency which is responsible for water uptake and swelling of the stratum corneum. There is also an increased transepidermal water loss related to the alteration of the barrier function. In the present prospective study, we evaluated sodium lauryl sulphate (SLS)-dependent changes in electrometric properties of skin. Single and iterative SLS challenges were performed. Measurements were made using a NOVA DPM on continuous mode for 5 min in order to assess both the baseline surface hydration and the rate of changes during probe occlusion. The present noninvasive instrumental evaluation of surfactant irritancy shows high sensitivity in each subject, but suffers from large inter-individual variability in the skin response following single and iterative sodium lauryl sulphate (SLS) challenges. The baseline surface hydration, that is almost unaffected 1 h after removing SLS patches, significantly decreases after a lag time of 24 h. The rate of water accumulation in the stratum corneum during the probe occlusion is significantly increased by SLS and is proportional to the SLS concentration and the number of iterative patches. Single water- or SLS-patch-tests fail to predict the skin response to cumulative SLS challenges and inter-individual variability is large for all electrometric variables.