Effect of hidromeiosis on sweat drippage during acclimation to humid heat.

Sweat rate and the rate of change in sweat drippage were studied during the acclimation of eight healthy male subject during exposure to heat during 10 consecutive days. During acclimation to hot humid conditions, the increase in total body sweat rate results in an increase in the rate of sweat drippage. We found, however, that on each day the drippage rate markedly decreased with time after the 1st h of heat exposure. This hidromeiosis was investigated as a function of the heat exposure time. No shortening of the onset time of hidromeiosis occurred with acclimation. With repeated heat exposures, the initial sweat rates in response to stress increased, and the subsequent decline became larger with higher sweat rates at the time of onset of hidromeiosis. Hidromeiosis appears to be a function of the degree of skin wettedness reached in the various local skin areas which determine the overall body skin wettedness upon which evaporative adjustments depend. Thus, the observed overshoot in total sweat rate as indicated by sweat drippage, and the subsequent hidromeiosis, result from initial oversweating in the poorly ventilated areas of skin. This sweat decline seems to be due to a reduction in output of the active sweat glands rather than to a reduction in active sweat gland number.