Effects of alcohol on thermoregulation during mild heat exposure in humans.

We investigated the effects of alcohol on thermoregulatory responses and thermal sensations during mild heat exposure in humans. Eight healthy men participated in this study. Experiments were conducted twice for each subject at a room temperature of 33 degrees C. After a 30-min resting period, the subject drank either 15% alcohol (alcohol session) at a dose of 0.36 g/kg body weight or equal volume of water (control session). Skin blood flow and chest sweat rate in the alcohol session significantly increased over those in controls 10 min after drinking. Deep body temperature in the alcohol session started to decrease 20 min after the onset of sweating and eventually fell 0.3 degrees C lower than in the controls. Whole body hot sensation transiently increased after alcohol drinking, whereas it changed little after water drinking. The increased "hot" sensation would presumably cause cool-seeking behavior, if permitted. Thus, alcohol influences thermoregulation so that body core temperature is lowered not only by automatic mechanisms (sweating and skin vasodilation) but also behaviorally. These results suggest that decreases in body temperature after alcohol drinking are not secondary to skin vasodilation, a well-known effect of alcohol, but rather result from a decrease in the regulated body temperature evidenced by the coordinated modulation of various effectors of thermoregulation and sensation.