In addition to techniques of skin temperature measurement, sweat gland activity is another indicator of sympathetic function.
Sympathetic stimulation causes increased sweat gland activity.
Increased sweat gland activity results in less resistance to the flow of an electrical current. Therefore, sweat gland activity may be assessed by passing a small electric current through the skin to measure resistance. Electrical skin resistance is related to the activity of the sweat glands. Interruption or retardation of the flow of impulses over sympathetic pathways to an area causes a marked elevation of resistance in that area. Stimulation of sympathetic pathways either locally or systemically lowers the resistance.