Electrical impedance applied to non-invasive detection of irritation in skin.

Healthy volunteers were subjected to irritation by sodium lauryl sulphate at concentrations in the range 0.002% to 5.0% applied in Finn Chambers for 24 h. Test sites were visually assessed 1 h and 24 h after cessation of exposure. At the same times electrical impedance was measured with a new impedance device which allows non-invasive local measurements to a controlled depth. Close agreement between concentration and an irritation index calculated from electrical impedance parameters was found over the whole concentration range for most test persons. At concentrations below 0.2%, visual scores were zero. These results suggest that electrical impedance can be used as an objective tool to record irritation, and further that electrical impedance might be a more sensitive method than the commonly used visual readings.