This test method is utilised to evaluate the ability of a skin care product to moisturise the skin in the stratum corneo, the epidermal layer of human skin, by measurement of electrical capacitance. Corneometry is utilised as a measurement technique to substantiate this claim via instrumental analysis.

 The measurement of skin hydration is based on capacitance measurement of a dielectric medium, in this application, the stratum corneum, the uppermost layer of the skin. With increasing hydration, its di-electric properties change. The measurement is based on the fact that water has a higher dielectric constant (81) than most other substances (mainly < 7). The instrument measures the change in the dielectric constant due to skin surface hydration changing the capacitance of a precision capacitor. Multiple readings are taken and the mean determined. The measurement can detect even the slightest changes in the hydration level of the skin.