Pathological acupuncture points on the ear have a changed electrical skin resistance. A sympathetic reflex is triggered in the body when pathological acupuncture points are stimulated with an electrical voltage (for example through residual stress of a metal or battery voltage ) or a color stimulus ( black, white). This will conclude in peripheral arterio-venous Shunts and  briefly lead to an increased amount of blood in the arterial-vascular system. The so -called RAC is triggered ”

[ source : Manfred Angermaier , ear acupuncture guide with French and Chinese points , 4th edition, 2007 , Urban & Fischer Verlag]