Using microelectromechanical systems technology, the authors have developed the world's smallest, lightest and lowest electric power-consuming laser Doppler blood flow sensor that can measure blood flow while the subject is moving. The influence of alcohol consumption on blood flow was investigated when measuring at a subject's earlobe. An arm-raising test in which the subject lifts an arm with the blood flow sensor attached to a fingertip was also investigated. This arm-raising test can't be conducted with a commercial instrument that uses an optical fiber because the measurement is easily affected by the movement of the fiber. Good correlation between blood flow at an earlobe, heart rate and breath alcohol content was obtained for light consumers of alcohol. Also, the influence of acetaldehyde on the blood flow was found in the arm-raising test for all subjects using the developed blood flow sensor.