JOURNAL OF COSMETIC SCIENCE 22 Table III Skin Conductivity Measured at Various Time Intervals After Application Time (min) Application 20 60 120 180 360 Untreated Mean 20.89 20.09 20.09 20.09 20.09 Standard deviation 4.64 4.58 4.54 3.98 4.36 HP-containing emulsion Mean 30.64 34.18 35.16 34.05 30.43 Standard deviation 4.91 4.88 5.13 4.35 8.59 % Difference from untreated 49.35 66.6 71.4 65.98 48.34 p(Tt) one-tail 9.58E-05 9.35E-07 3.53E-07 5.19E-07 4.44E-04 CCT-containing emulsion Mean 30.02 32.77 34.45 32.46 29.33 Standard deviation 5.02 5.09 5.41 6.81 6.71 % Difference from untreated 45.35 58.62 66.76 57.13 41.98 p(Tt) one-tail 3.59E+01 1.77E-01 3.74E-01 2.41E-01 3.20E-01 Control emulsion Mean 20.36 20.41 20.68 21.07 20.88 Standard deviation 4.76 4.37 4.42 4.12 4.85 % Difference from untreated 3.47 3.71 5.1 7.09 6.11 p(Tt) one-tail 1.86E-04 5.82E-06 2.64E-06 1.55E-06 2.15E-03 Figure 4. Percent increase in skin conductivity upon application of HP or CCT. Moisturizers function by increasing the epicutaneous hydration that can be caused by either of two mechanisms as reviewed in reference 7: (a) by providing the skin hydration from their water phase, in which case we observe a reduction in transepidermal water loss

MOISTURIZING EFFECTS OF HYDROGENATED POLYISOBUTENE 23 (TEWL) or (b) by increased occlusion, thereby causing a decrease in TEWL. When we measured TEWL upon application of HP, as well as of CCT, we observed that the TEWL decreased signifi cantly, proving the effectiveness of HP and CTT in retaining skin hydra- tion. This effect was longer-lasting in the case of HP and was maintained at a 30% lower level as compared to untreated skin for up to 6 h after application. Such reduction in TEWL has been reported previously upon application of moisturizers in several instances (2,6,5,19). The increase in skin capacitance and conductivity upon increased hydration resulting from application of moisturizers has been studied previously (1). Humectants such as glycerin, pyrollidine carboxylic acid, or urea in o/w emulsions, in comparison to petro- leum jelly have proven to be effective in increasing skin capacitance in normal adult forearm skin (20). Matsumoto et al. in 2007 reported an increase in skin capacitance in infantile leg sites upon application of an o/w cream containing glycoceramide, while heparinoid-containing creams were more effective in the chest regions (3). While this variability in effectiveness with the site of application may be explained to be a result of the absorbtion of humectants by the skin, in the case of emollients like HP or CCT, due to their high molecular weight, we may speculate that the increase in capacitance is a result of the formation of an epicutaneous fi lm rather than absorbtion. However, further studies on skin absorption and penetration will help to ascertain this hypothesis. ACKNOWLEDGMENTS The fi nancial support from INEOS Oligomers to carry out this work is gratefully acknowledged. We thank Dr. Stephen M. Greenberg for critically reviewing this manu- script and for his valuable comments. Figure 5. Polarized photographs taken by View Charm: baseline (upper row), untreated, versus 6-h post-treatment (lower row).