Consensual reaction of the heat refers to the fact that heating the skin of one extremity reflexively increases the blood flow in the contralateral extremity.

The mechanism of consensual reaction is thought to be the neural reflex mediated by sympathetic nervous system, which has reflex centers above C5 cord. To find out the effects of consensual reaction of the heat on cardiovagal response, sudomotor response and nerve conduction, we applied infrared therapy on one upper extremity in normal 27 men and compared with the changes of oral temperature, pulse rates, skin temperature, sensory nerve conduction and sympathetic skin response.

The results showed no change in oral temperature and pulse rate. However, increases in skin temperature and nerve conduction velocity in contralateral upper extremity were observed, which suggested the effects of consensual reaction of the heat on contralateral nerve conduction. In sympathetic skin response, the decrease of minimum latency in the contralateral upper extremity was observed and it also suggested the increase of nerve conduction velocity of sudomotor fiber by the effects of consensual reaction of the heat.