JOURNAL OF COSMETIC SCIENCE 20 QUANTIFICATION OF THE MOISTURIZING EFFECT Measurement of transepidermal water loss (2,4,5) and of increased skin conductivity (1) are useful tools in assessing the effectiveness of moisturizers in skin hydration. Hence we further analyzed the o/w emulsions HP and CCT or a control formulation for skin mois- turization using these two techniques. Data presented below include the effects of HP and CCT on reduction in TEWL (Table II Figure 3) and skin conductance (Table III Figure 4). Mean TEWL obtained for the untreated site at each time interval was sub- tracted as a correction factor from the TEWL obtained for the HP- or CCT-applied site, to derive the respective corrected means. Upon application of HP or CCT there is a gradual decrease of TEWL and an increase in skin conductance with time. A maximal decrease of TEWL by 33.36% was observed with HP treatment compared to the control at the 3-h time point. This reduction was maintained for up to 6 h. It can be clearly seen that, at all time points, both HP and CCT were signifi cantly better than the control for- mulation in reducing TEWL. Furthermore, at all time points, HP demonstrated greater reduction when compared to CCT. Six hours after application, HP was signifi cantly better (p 0.001), exhibiting a long-lasting moisturizing effect. Corneometer readings of the HP- or CCT-applied skin were taken as a measure of skin conductivity and were normalized against untreated skin, as for TEWL measurements. These readings increased dramatically by 45% to 50% within 20 min of CCT or HP applica- tion, respectively, compared to that with the control formulation (3.47% only). At all time points of analysis, HP performed signifi cantly better than the control formulation (p 0.001), whereas the difference of CCT from the control showed a signifi cance probabil- ity value of p 0.5. The mechanism by which both compounds contribute to the capacity of the skin to hold water may not just be related to their fi lm-forming properties, but to their effect on the emulsion properties and the organization of water droplets in it. The Table II Transepidermal Water Loss Measured at Various Time Intervals After Application Time (min) Application 20 60 120 180 360 Untreated Mean 8.22 8.23 8.23 8.23 8.22 Standard deviation 1.03 0.92 1 1.08 0.96 HP-containing emulsion Mean 5.27 4.17 3.68 3.43 4.61 Standard deviation 1.1 0.99 0.69 1.15 1.46 % Difference from untreated -28.32 -43.23 -49.98 -53.33 -37.26 p(Tt) one-tail 1.88E-04 1.18E-06 3.21E-05 2.58E-05 1.86E-03 CCT-containing emulsion Mean 5.51 4.48 3.91 3.47 5.19 Standard deviation 0.67 1.07 1.04 0.96 0.79 % Difference from untreated -24.59 -38.46 -46.46 -52.55 -29.04 p(Tt) one-tail 2.38E-01 3.03E-01 2.70E-01 4.69E-01 1.51E-01 Control emulsion Mean 7.73 7.36 6.97 6.77 7.31 Standard deviation 1.32 1.33 1.55 1.42 1.34 % Difference from untreated -8.57 -12.98 -17.63 -19.97 -13.59 p(Tt) one-tail 1.42E-02 2.01E-02 1.56E-02 6.28E-02 1.57E-02

MOISTURIZING EFFECTS OF HYDROGENATED POLYISOBUTENE 21 correlation between the effect on physical properties of the emulsion that is translated to an elevation in viscosity and an effect on the skin should be studied further. VISUAL EVALUATION OF SKIN TEXTURE To further evaluate visual differences, skin treated with HP, CCT, or the control was vi- sualized using a Charm View camera and photos captured both before and after the test. These show clear difference in the effects of HP and CCT when compared to the control (Figure 5). While dried pre-treated skin appears thinner, peeled off, and was therefore rough in texture, skin hydrated by application of HP or CCT exhibited a fi ne texture with a clear contrast between lines and planes. It is clear that HP is more effective in improv- ing skin texture and hydration upon comparison to the control emulsion-treated site, untreated skin, or CCT-treated skin. DISCUSSION When designing a formulation to hydrate the skin, formulators often combine fi lm- forming agents with humectants for possible synergistic effect. Oftentimes, the effect of the vehicle itself or other ingredients such as emollients is neglected. For example, in a study comparing different commercially available moisturizing products (1), it was demonstrated that there might not be a direct correlation between the content of the moisturizing agents and that the design of the formulation can have a key effect. In the present study, therefore, we attempted to analyze the isolated effects of HP on skin moisturization and have compared it to the emollient ester CCT. HP causes the desired effects of decreased emulsion droplet size and increased viscosity in o/w emulsions. Figure 3. Percent reduction in TEWL upon application of HP or CCT.