Teruko Tamura

Effect of humidity sensation on hormonal responses in saliva and urine

Abstract The purpose of this study is to clarify the psychological and physiological effects, especially the endocrinological effects, of the humidity sensation on human skin by analyzing salivary and urinary hormones under two different humidity conditions. Twelve healthy female subjects, aged 21–22 years old, were exposed for 90 min to two different humidity conditions: a variable condition of 30–70% RH at 34°C and a constant condition of 30% RH at 34°C. The body weight loss, R-R interval of heart rate variability (HRV), salivary cortisol concentration, secretory immunoglobulin A in saliva (S-IgA), and urinary catecholamine fraction were measured and subjective evaluation of thermal, dampness and comfort sensations were made. According to the sweating response, the subjects were divided into two groups. Group A subjects sweated a lot in the increasing humidity condition, while group B subjects showed a higher sweat rate under the constant humidity condition. As a result of analyzing data separately for each group, it was shown that both S-IgA in saliva and the index of sympathetic nervous activity obtained from HRV changed in relation to the sweating rate of the subjects rather than to the degree of the discomfort felt by the subject. No significant difference in the amount of adrenaline, noradrenaline or dopamine was obtained through urine analysis.