178 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 6O 5O c: ,-! o ._• 0 10 ! I I I I 0 2 4 6 8 10 12 Time (Hours) Figure 1. Change in the permeation of water through micro-Yucatan pig skin stored at -15øC for a period of four weeks. ß initial, O one week, ß two weeks, V three weeks, ß four weeks. Each error bar represents the standard error of the mean. weeks were significantly different from the initial values. An increase in flux of both permeants was noticed with time. The ratios of water to SA flux are displayed in Table I. Most of the ratios calculated for the second and fourth weeks were significantly different from the initial ratio calculated. EFFECT OF STORAGE TEMPERATURE ON THE PERMEATION OF WATER AND SALICYLIC ACID THROUGH MICRO-YUCATAN PIG SKIN WHEN THE SKIN WAS DERMATOMED BEFORE STORAGE Plots of the cumulative amounts of water and SA permeating through micro-Yucatan pig skin over time were linear during the four-week period of testing (r 0.995 in all cases). Water and SA fluxes were calculated for all cases and plotted as a function of time in Figures 4 and 5, respectively. Skin stored at - 15 øC was significantly more permeable to both molecules after one week of storage, whereas the permeability of the skin stored at 4øC was almost unchanged for the four-week period of study. Only one point was significantly different from its initial value. During the study, the flux ratios obtained were in agreement with the data obtained from the rates only.

ASSESSING SKIN BARRIER INTEGRITY 179 • 5 • 4 I I I I I 0 1 2 3 4 5 Time (Weeks) Figure 2. Effect of storage temperature on the permeation of water through micro-Yucatan pig skin (skin stored before dermatoming). ß 4øC, ¸ -15øC. * Statistically significant value from the initial result. Each error bar represents the standard error of the mean. EFFECT OF STORAGE TEMPERATURE ON THE PERMEATION OF WATER AND SALICYLIC ACID THROUGH MICRO-YUCATAN PIG SKIN WHEN THE SKIN WAS DERMATOMED AND DRIED BEFORE STORING Plots of the cumulative amounts of water and SA permeating through micro-Yucatan pig skin over time were linear during the four-week period of testing (r 0.987 in all cases). Water and SA fluxes were calculated and plotted as a function of time in Figures 6 and 7, respectively. It was clear that storing skin for a period of four weeks at 4øC after drying and dermatoming did not affect its permeability for either water or SA. When skin was stored at - 15 øC, its permeability to water was unchanged, but its permeability to SA was somewhat affected. The flux ratios did not change remarkably during the experiment. PERMEATION OF WATER AND SA THROUGH VENTRAL AND DORSAL YUCATAN PIG SKIN Cumulative amounts of water and SA permeating over time through ventral and dorsal pig skin were obtained. The values of water and SA fluxes were calculated and are