Experimental study on improving effect of cooling garment on thermal comfort and salivary IgA concentration

Phase change cooling garments (PCCGs) can effectively alleviate the heat stress of manual workers in high-temperature environments. The PCCGs bring about cold stimuli to users, which not only affect the thermal perception and thermoregulation of the human body, but also could have some influence on the nervous and endocrine system, and even on the immune system. This study explores the effects of PCCGs on thermal comfort and respiratory mucosal immune function. Experiments were conducted in a climate chamber at 33 °C with a relative humidity of 50 %. Twenty participants were recruited and experienced three experimental conditions (NG, normal garments; PCCGs with a cooling temperature of 21 °C, PCCGs-21 and 17 °C, PCCGs-17). Subjects took packing activity with a metabolic rate of around 2.7 met. Subjective questionnaires (thermal sensation votes, thermal comfort votes) were collected, and physiological parameters (skin temperature, core temperature) were tested. Besides, the salivary samples were gathered to measure the Salivary secretory immunoglobulin A (S-IgA) concentrations using enzyme-linked immunosorbent assay (ELISA). The results showed that the use of PCCGs affected the S-IgA concentration significantly. Compared with the NG condition, the S-IgA concentrations increased by 55.9 % and 46.4 % in the PCCGs-21 and PCCGs-17 conditions, respectively. Additionally, the S-IgA concentrations were the highest when participants felt slightly warm or comfortable. The S-IgA concentration of the comfortable state was 98.5 % higher than that of the intolerable state. The S-IgA concentrations were also found to be negatively correlated with local skin temperatures of the back and chest (p < 0.001). The use of PCCGs has a positive influence on improving thermal comfort and S-IgA concentration.