Influence on the Sweating Function by the Successive Application of Artificial CO₂ Bath Salts

Abstract

  Using healthy volunteers, we examined the influence of emulsified oil and a low concentration of CO₂ gas on cutaneous blood flow in the forearm. The forearm of each subject was immersed in 25 liters of warm water containing either 10 ppm emulsified oil or 60 ppm CO₂ gas or both. Forearm cutaneous blood flow was measured for 20 minutes. Emulsified oil had no effect on cutaneous blood flow, whereas CO₂ gas caused a gradual and significant increase. When CO₂ gas was used with emulsified oil, cutaneous blood flow was significantly increased in comparison to CO₂ alone, suggesting that emulsified oil enhances the vasodilation caused by CO₂. We then prepared bath salts releasing CO₂ and emulsified oil, and tested for their influence on sweating function in sixteen healthy adults. Each subject bathed daily 10 minutes either in tap water (control group) or in tap water dissolving bath salts releasing CO₂ and emulsified oil (bath-salts group) at 40°C for successive 14 days. A sweating test was performed before and after the session of bathing. In the bath-salts group, the baseline tympanic temperature after successive bathing tended to be lower than that before successive bathing. Although the rise of body temperature during the heat exposure was not different between the groups, sweating rate was significantly greater after successive bathing. The analysis of the rate of sweat expulsion suggested that the greater sweat rate after the successive bathing is mediated by the central mechanism for sweating. Such changes were not observed in the control group. Thus, successive bathing using bath salts that release CO₂ and emulsified oil may have a beneficial effect on sweating function.