JOURNAL OF COSMETIC SCIENCE 18 0.2 ml of each test product was dispensed to each test site using a 1-ml volumetric sy- ringe. This amount was evenly applied by a technician using a fi nger and rubbed until absorbed into the skin. Measurements were taken on the sites prior to product application and at intervals of 20, 60, 120, 180, and 360 minutes. MEASUREMENT OF TRANSEPIDERMAL WATER LOSS (TEWL) The rate of water evaporation from the skin surface was measured using a Tewameter (Courage-Khazaka). This instrument is designed to follow water evaporation from the skin by applying the principle of water diffusion in an open chamber. The density of wa- ter gradient within the skin surface is analyzed indirectly by two pairs of sensors, for temperature and relative humidity. Data measured are analyzed by a microprocessor. MEASUREMENT OF SKIN CONDUCTANCE Moisture content in the skin was measured using a Corneometer CM 825 (Courage-Khazaka) This instrument is designed to measure skin surface hydration via capacitance measure- ment of a dielectric medium. This measurement can capture minor changes in hydration levels, with relatively high reproducibility in a short measurement time of around 1 sec. DATA COMPUTATION AND STATISTICAL ANALYSIS Sorted data for TEWL and conductance were tabulated for each time point of application of the control emulsion, HP-containing emulsion, and CCT-containing emulsion, respec- tively, and the means were recorded in each case. Statistics were calculated using an analysis package provided by Microsoft Excel 2003, following the recommendations of the International Federation of the Society of Cosmetic Chemists in their monograph Principles of Product Evaluation: Objective Sensory Methods (14). In this approach statistical signifi cance was evaluated using a one-tailed T-test to assess net change from the baseline. Statistical signifi cance was defi ned at p £ 0.05 (corresponding to a 95% or greater confi - dence level). EFFECT OF MOISTURIZATION ON SKIN TEXTURE The visual effect of moisturization was observed using a Charm View video microscope (Moritex). This instrument is designed to visually magnify the skin on a video screen, allow- ing the monitoring of minor changes in skin texture. It is equipped with a 1/3-inch CCD color-image sensor with three polarizing fi lters that allow for skin texture to be observed clearly. RESULTS We here analyzed for the fi rst time and compared formulations consisting of HP with CCT or a control formulation, for their physical properties and their effect on TEWL and skin conductivity as a measure of skin moisturization. The results are shown below.

MOISTURIZING EFFECTS OF HYDROGENATED POLYISOBUTENE 19 EFFECT OF THE EMOLLIENTS HP AND CCT ON THE PHYSICAL PROPERTIES OF THE FORMULATIONS Both HP and CCT in o/w emulsions at 8% increased emulsion viscosity. The emulsion struc- ture was monitored microscopically, at 400´ magnifi cation, shown in Figure 2A. This in- crease may not only affect the emulsion’s stability, but possibly can also contribute to the microstructure of the emulsion, and hence its fi lm formation on the skin, and can affect inter- action with the skin. Further, we analyzed emulsion droplet size, in terms of the average diameter of the drop- lets. HP or CCT incorporated emulsions showed a dramatically reduced droplet size of 18.58 ± 2.02 or 26.7 + 4.05 (arbitrary units), respectively, compared to the control that exhibited 65 ± 9.56 (arbitrary units) (Figure 2B). Thus HP was much more effective than CCT in the reduction of emulsion droplet size. Depending on the substance or method of study, emulsion droplet size is shown to enhance or retard the interaction properties of emulsions with the skin. Although emulsion droplet size is cited, in some instances, to be directly correlated to skin penetration (15,16), confl icting reports exist that describe the importance of the proportion of other ingredients in the formulation (17), surface charge (18), or exposure of interactive species on emulsion droplets in affecting skin pen- etration and causing a decrease in TEWL, thus affecting hydration. Whatever the effect of reduced emulsion droplet size on skin penetration may be, the signifi cant reduction of droplet size upon HP incorporation compared to the control emulsion is interesting, and additional studies on its ability to penetrate or interact with skin may reveal the intrica- cies of its mechanism of action. Figure 2. (A) Visualization of o/w emulsions comparing 8% HP, 8% CCT, and control, at 400× magnifi - cation. (B) Emulsion droplet size comparison.