PERMEABILITY OF EPIDERMIS 857 Figure 1. 2 0 5 ß H20 wffh sat. Octonol a pure H20 20 wHh sat Octanol • o ß 3 40 3.50 3 60 1000 TøK Effect of small concentrations of octanol (0.00531) on the permeability constant of water through stratum comeurn at various tcmperatnres J(p = 2.4 X I0 '! cm hr" •, PURE 8UTANOL / AFTER 0.005 M OCTANOL Kp = 4.8 x IO o I 2 $ 4 5 6 7 6 9 I0 HOURS TIME Figure 2. Effect of 0.005M octanol on the flux of butanol stratum corneum membrane was used and octanol-containing and octanol-free butyric acid solutions were exchanged after each perme- ability constant was obtained. The permeability constant increases after octanol is added, then returns to its original value as the octanol is washed out. The process can be repeated many times.

8,58 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS •.• 5.0 [,, ,• E 4.0 % 30 : 1.0 •t•"""• '7' 0'---0'0' BUTYRIC ACID 0 I I I I I I I I I 2 3 4 5 6 7 DAYS IMMERSION BUTYRIC ACID (with octanol ) Figure 3. Permeability of butyric acid in the presence of saturated aqueous octanol The reason why the sorption of nonpolar molecules like octanol doubles the diffusion rates of water and other polar molecules is not known. A possible explanation might be that low molecular weight, lipid-soluble molecules can plasticize the rather high molecular weight skin lipids (average carbon no. = C20 -- C22) and in so doing permit greater internal hydration and expansion of the keratin matrix. , Extraction of Lipida from the Stratum Corneum If the relatively small amount of nonpolar solutes sorbed from dilute aqueous solution can measurably plasticize the membrane, it is not surprising that these same liquids applied directly can solubilize and extract significant amounts of lipid. The partially or completely delipidized tissue is a very different and very inferior permeability bar- rier in comparison to the untreated tissue. Figure 4 illustrates the increase in water permeability after the stratum comeurn was held in continuous contact with each of four oo7 5 J / a Chloroform-Methono[ 006• [ . Ether % 0 04 • OO2 0 t 2 3 4 5 6 7 Fig•tre g. Effect of various delipidizing solvents on the permeability of water. The h,'s are respectively 120, 18, •.8, and 1.? X 10-a c•n/br for chloro[orm-methanol through ethanol