On the Transfer Function of Human Skin

Abstract: University of Washington Department of Meteorology and Climatology Seattle 5 Washington ANNUAL REPORT To the U. S. Army Chemical Warfare Laboratory Army Chemical Center Maryland Contract DA 18-108-405- CML-666 I. Introduction and Definitions This report tries to clarify aspects of skin penetration. The transfer of water seems to differ drastically from that of other substances. Therefore the first part is devoted to water the second to other substances. Water and water vapor are believed to move through intact skin surface by: a) glandular secretion such as sweat gland b) sorption and desorption in the horny layer c) diffusion through the hornj layer. With proper care all three avenues can be sufficiently well differentiated. Sweating can be partly controlled by low room temperature atropine and selection of a body area not prone to sweating. Sweat amount is also measured in blank tests on the opposite limb furthermore by counting sweat droplets. Horny layer sorption and desorption is a saturation process after the skin enters a new environment. After sweat and sorption are evaluated or prevented there remains a flow of liquid water or vapor through the skin. This flow seems to depend on the water concentration of the medium touching the skin. This concentration will be defined for water solutions as well as for air as relative humidity ra. In all but a very few test persons water and water vapor from solutions or air of more than ra = 90 per cent pass into the skin. Since the point of no transfer of 90 per cent relative humidity or about four osmolar exceeds by far the body osmolarity the transfer should be active. The active process or pump seems to be separated from the environment by a barrier. This barrier appears to be part or the whole of the stratum corneum conjunctum. Barrier and pump seem to be different entities with the following characteristics: (1) the barrier: its resistance is about ten times higher on arm or leg than on palm or sole; about 3-5 times higher for the same skin area under dry than under moist conditions; invariant to four hours of ethyl ether exposure; absent for about three days after stripping off the stratum conjunctum. (2) The pump: its intensity is increased (i.e. the neutral relative humidity is lowered) in persons having edema from toxemia pregnancy internal disorders and menstruation; the pump intensity is lowered (i.e. the neutral relative humidity is raised to nearly 100per cent) in myxedema; after skin stripping; in two of our persons after a four-hour exposure to ethyl ether. After stripping the pump comes back to normal in about six days. The rubefacient nicotinic acid did alter neither barrier resistance to water vapor nor the pump. ... ___MH

Zurück | Weiter