Research Summary
Non-invasive methods to evaluate skin hydration by measuring electrical properties are widely used in the cosmetic industry. However, there is still some controversy about factors that affect these measurements. For example, concerns have often been expressed about the possible confounding effect of salts, either in the formulation or on the skin. Ionized salts on the skin may increase electrical conductivity and lead to changes in electrical properties that are not related to increased water content.
We have conducted a systematic study to investigate the effects of salt, specifically sodium chloride, and glycerin on the electrical properties of skin as measured by the three most commonly used instruments: the Nova © DPM 9003, the Corneometer © CM 825, and the Skicon © 200. Formulations containing varying concentrations of salt (0–3%) and glycerin (0–10%) were tested for their effects one and two hours after a single application.
The results showed that salt lowered the readings in the absence of glycerin, but increased the readings when glycerin was present. For all three instruments, a linear correlation was found between the measurement and the glycerin level, regardless of the presence of salt.
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