A method and device for detection of drowsiness of a person, based on a relationship between distal temperature and heart rate and on a balance between body heat loss and body heat production, wherein the distal temperature in a predetermined distal region of the person is monitored as a measure for body heat loss, and the heart rate of the person is monitored as a measure for body heat production, wherein drowsiness in the immediate future is concluded when a change of distal temperature passes a first threshold and, subsequently, a change of the heart rate passes a second threshold or, subsequently, the change of the distal temperature is larger than the change of the heart rate.