Sweating Distribution and Active Sweat Glands on the Head of Young Males in Dry and Humid Environments

Abstract

Sweating is one of the mechanisms of thermoregulation for heat dissipation to maintain body temperature. Sweat rate is known to be different according to the region of the human body, with the highest rate on the back and the lowest rate toward the periphery. The head has a greater sweat response than all other body segments except the hands and feet. Many studies have reported forehead sweating as representative of sweating on the head

however, there is a lack of information about regional differences in sweating on intra-segmental hairy sites. The purpose of this study was to investigate the effects of humidity on sweat distribution and active sweat glands on the head during passive heating in a hot-dry environment (32 °C, 30%RH) and a hot-humid environment (32 °C, 85%RH). Passive heating was induced by immersing in hot water (42 °C) for 1 h. Despite differences in humidity, the results showed that there was no significant difference in sweat rates for the head, and the total sweat rate was significantly greater in the dry environment than the humid environment. The local sweat rate was greater in the frontal region than the vertex region of the head. Active sweat glands were counted by the iodine-impregnated paper method, and the number in the humid environment was greater than that in the dry environment. The sweat distribution pattern of the head was different compared with that of the entire body. These findings could be applied to headgear design for reducing the heat stress of the wearer. The thermal comfort of headgears can be improved by adding a vent hole to the front and back of headgears for ventilation, and the top of headgears should be made of breathable material with enhanced durability.