In vitro calibration of the capacitance method (Corneometer CM 825) and conductance method (Skicon-200) for the evaluation of the hydration state of the skin.

BACKGROUND/AIMS: A major problem with electrical measurements of the capacitance of the skin using the well kwown capacitance method (Corneometer) resides in the fact that the results of this instrument are expressed as arbitrary capacitance hydration units that are not directly related to real electrical units or to the water content of the horny layer. The purpose of this study was to establish a calibration of the capacitance method using a simple in vitro simulation system of the horny layer.

METHODS

The calibration of capacitance and conductance methods was carried out using cellulose filter papers saturated with water, aqueous solutions and liquids of different dielectric constant (sorption and desorption experiments).

RESULTS

Using this in vitro method, correlations were established between the capacitance values and the quantity of water adsorbed on the filter and with the dielectric constant of the liquid saturating the filter paper. High correlations were observed during sorption and desorption experiments between the capacitance and conductance measurements.

CONCLUSIONS

In vitro calibration of the capacitance method is now possible with this simulation model of the horny layer. Furthermore, determination of the range of sensitivity, accuracy, repeatability and depth of detection of the measuring probe of the capacitance and conductance method were carried out.