222 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table I Recovery of Lanolin From Tape Strippings Lanolin found (mg) Strippings Individual Cumulative Cleanings 1.03 1.03 1 to 3 2.47 3.50 4 to 6 0.43 3.93 7 to 9 0.15 4.08 10 to 12 0.07 4.15 13 to 15 0.06 4.21 16 to 18 0.05 4.26 19 to 21 0.02 4.28 22 to 24 0.01 4.29 25 to 27 0.01 4.30 28 to 30 0.03 4.33 cumulative recovery of "lanolin" was 0.18 mg (note: this is not a constant figure see below), and after deducting this "blank" from the results of the original test with lanolin, the net recovery then becomes 4.15 mg out of 4.20 (98.8%). The weight of lanolin unaccounted for is only 50 Ixg, about the same as the limit of determination, and 3 m o 3 6 9 12 15 18 21 24 27 30 Strippings Figure 1. Lanolin removed by tape strippings.

PENETRATION OF LANOLIN 2 2 3 Table II Apparent Lanolin in Control Strippings Apparent lanolin found (mg) Strippings Individual Cumulative 1 to 3 0.09 0.09 4 to 6 0.05 0.14 7 to 9 0.02 0.17 10 to 12 0.02 0.18 13 to 15 Trace 0.18 16 to 18 Not detected 0.18 19 to 21 Not detected 0.18 22 to 24 Not detected 0.18 25 to 27 Not detected 0.18 28 to 30 Not detected 0.18 so no more than this, if any, appears to have penetrated the stratum corneum into deeper layers of the skin. Further tape strippings were also made from two different individuals, and yet another set of strippings was made from the original test subject, in all cases without preap- plication of lanolin. The number of strippings in each case was limited to six, com- prising two groups of three, each group being analyzed for apparent lanolin content. The results are shown in Table III. These figures demonstrate not only a large difference between individuals, but also that results from the same individual at different times can vary by a factor of more than three. In any case, interference with the test method used is relatively small. 0.1- -- I I i I 3 6 9 12 15 I 1 I I 18 21 24 27 30 Strippings Figure 2. Apparent lanolin in untreated skin.