Sweating in hot baths

Abstract

Sweating of human volunteers immersed to the neck in hot water declined markedly after reaching a peak in the 1st hr of exposure. This decline always occurred in fresh water regardless of level of thermal stress. Sweating in the 3rd hr of exposure was about the same whether the water was hot in the 1st 2 hr (sweat glands active) or cool (sweat glands inactive). Thus “fatigue” was not responsible for the decline. It is suggested that observations of decline of sweating in warm-humid air environments, attributed to “sweat gland fatigue,” in reality may have been owing to soaking of the skin with sweat. The mechanism of suppression appears more complex than blockage of the sweat ducts by swelling of the corneum. Rather, there is an association between the amount of decline and conditions favoring diffusion of water to deeper strata of the skin. For example, adding salt to the water reduced the decline; no decline occurred in 15% NaCl. Submitted on March 6, 1961

Some effects of exposure to an environment of saturated air at mouth temperature

“…The relation between this phenomenon and previous descriptions of sweat 'fatigue' is discussed by Collins & Weiner (1960) and Hertig, Riedesel & Belding (1961). Reproducibility of results There was considerable variation between the curves relating rate of weight loss to temperature obtained on different occasions.…”

The relation between sweat rate and weight loss when sweat is dripping off the body

“…The effect of hydration on the palmar skin was described by Randall & Peiss (1957) and has since been confirmed for the general skin surface (Sargent, 1962). If the skin is covered with a film of water or dilute saline, the ability to produce sweat diminishes exponentially with time (Hertig et al 1961;Brebner & Kerslake, 1964). The rate of decline depends on whether the subject is sweating or not, but at moderate and high sweat rates the time constant is probably independent of the sweat rate (Brebner & Kerslake, 1968).…”

“…Elsewhere the skin is kept wet, and sweat production will be progressively impeded. The decline in maximum sweat production from wet skin proceeds exponentially with time (Brebner & Kerslake, 1964, 1968) and at lower rates of drive the suppression behaves similarly (Hertig, Riedesel & Belding, 1961;Brebner, Kerslake & Soper, 1962;Sargent, 1962). The rate of sweating from the wet skin should therefore be related not to the capsule sweat rate, 0, but to a time dependent function of it, 0.e-tlk.…”

The effects of soaking the skin in water at various temperatures on the subsequent ability to sweat

“…The present paper is concerned only with the depression in sweating caused by wetting the skin. Hertig et al (1961) found that the sweat rates of subjects immersed in warm water (360-37.2°C) declined exponentially towards zero. When the experiment was preceded by a period of immersion in thermally neutral water (32-34°C) the sweat rates in the warm water were lower, and it appeared that the thermally neutral water suppressed sweating in the same way as did warm water.…”

“…The resulting decline in sweat production can be seen clearly with immersion in water or dilute saline (Hertig, Riedesel & Belding, 1961). It has also been demonstrated in humid air (Sargent, 1962), although here it is sometimes masked by an increase in body temperature with little change in the rate of sweat production, and the picture may be complicated by such factors as dehydration (Pearcy, Robinson, Miller, Thomas & IDeBrota, 1956), fatigue of the secretory celis of the sweat glands (Gerking & Robinson, 1946;Peter & Wyndham, 1966) and excessive body temperature (Ladell, 1955).…”