WATER-HANDLING PROPERTIES OF VERNIX CASEOSA 655 then allowed to completely desiccate. The difference between the initial weight and the dry weight was referred to as the total water content of the test preparations. Data recorded during three hours of measurement were used to obtain % water remaining at each time point. The results were expressed as % water content in the test emulsions over a period of time. Temperature and relative humidity during each experiment were noted. Water vapor transport. Water vapor transport was measured using a quantitative method developed in our laboratory (submitted to the Journal of Cosmetic Science). Briefly, hex­ agonal polystyrene disposable weighing dishes (20 mm length x 20 mm width x 10 mm height) were half filled with distilled water. Double layers of N-terface®, a porous high-density polyethylene interface dressing, were glued to the upper edges of the dishes. Following two hours of equilibration at room temperature, native vernix, the standard emulsions, and vernix-like lipid-in-water emulsions or the HIPEs were uni­ formly applied onto the N-terface® dressing at 25 mg/cm2 using a spatula. Gravimetric measurements were recorded at time 0, 2, and 4 hours after the application of the test samples. The rate of weight loss was calculated for each test system as weight per unit area per time (g/m2/h) and compared to that obtained from native vernix. Temperature and relative humidity during the study were recorded. RESULTS PREPARATION OF HIPEs Stable HIPEs were successfully prepared by use of the following emulsifier combina­ tions: • 4% PEG-7 hydrogenated castor oil and 5 % polyglyceryl-4-isostearate (and) cetyl dimethicone copolyol (and) hexyl laurate • 2% cetyl dimethicone copolyol and 0.8% PEG-7 hydrogenated castor oil • A combination of cetyl dimethicone copolyol with either polyglyceryl-3-diisostearate or polyglyceryl-4-isostearate (and) cetyl dimethicone copolyol (and) hexyl laurate • A combination of PEG-30 dipolyhydroxy stearate and sorbitan sesquioleate The HIPEs were prepared and evaluated for stability, visual appearance, and the water­ handling properties of the finished preparations. The addition of colloidal oatmeal changed the emulsion stability and caused microbial contamination. Therefore, it was not suitable for use in the HIPEs. Stable HIPEs could be obtained by the use of oil phase containing either non-vernix-like lipids commonly used in conventional emulsions or vernix-like lipids similar to those of native vernix lipids. Table II summarizes the representative preparations formulated. They are grouped based on the type of lipid used: non-vernix-like lipids, vernix-like lipids, or a combination of both lipid types. The HIPEs provided both high stability and a water release profile similar to that of native vernix. Stable HIPEs with approximately 78% hydrophilic phase were obtained in the system, using vernix-like lipids with the combination of PEG-30 dipolyhydroxystearate and sorbitan sesquioleate as the emulsifier phase. All HIPEs formulated in the study, categorized and listed based on the formulation strategies, are provided elsewhere (24). ST ABILITY OF HIPEs All HIPEs shown in this report were stable at room temperature (25° ± 3°C) for at least three months. Phase separation or change in visual viscosity could not be detected.

656 JOURNAL OF COSMETIC SCIENCE Table II All Ingredients and Composition of Selected Stable HIPEs Ingredients II III IV V VI VII Oil phase Mineral oil 7.11 6.4 5.61 5 3.5 Petrolatum 5 5 5 Lanolin 2.7 2.7 2.7 2 2 2 2 Cetyl alcohol 3.49 3.49 3.49 Beeswax 1.71 2.5 3 3 4.2 4.2 Sgualene 4 4 4 3.5 Linoleic acid 1 1 1 0.8 Cholesterol 4 5.5 7.5 6 Ceramide III 1 1.5 Capric/capylic triglyceride 2 2 1.5 Cholesterol sulfate Polyglyceryl-4-isostearate (and) cetyl dimethicone copolyol (and) hexyl laurate 2 2 2 Cetyl dimethicone copolyol 1 PEG-30 dipolyhydroxystearate 1.5 1.5 1.5 1.5 Sorbitan sesquioleate 0.5 0.5 0.5 0.5 Water phase Methyl paraben qs. qs. gs. qs. qs. qs. qs. Propyl paraben gs. gs. gs. qs. gs. gs. gs. Sodium chloride 0.7 0.7 0.7 Magnesium sulfate 0.5 0.5 0.5 0.5 Glycerin 7 7 7 5 5 2.5 2.5 Water 70 70 70 70.5 70.5 75 75 Formulation number VII was stable after being subjected to three cycles of the accel- erated condition (freeze-thaw examination). WATER RELEASE PROFILES Water release profiles of native vernix, typical emulsions, and HIPEs are shown in Figures 1 and 2. Figure la presents the water release profiles of native vernix compared to those of standard 0/W and W /0 emulsions. All data are expressed as a percent of the remaining water content within test samples over a period of three hours. Native vernix, containing water, approximately 82% w/w, released water at the same rate as the W/0 emulsion in the first 30 minutes of measurement. After three hours, vernix and the W/0 emulsion lost 19.5% and 14% of the total water content (w/w), respectively. Vernix and the W/0 emulsion showed similar slow water release profiles. In contrast, the 0/W emulsion released as much as 30% of total water content within the first 30 minutes. Water release profiles of the HIPEs are shown in Figure lb. The results show different profiles among all of the preparations. HIPEs prepared using vernix-like lipids showed slower water release rates than preparations using non-vernix-like lipids. Formulation number VII released water at 9% and 21 % of the total water content by the end of 30 minutes and three hours of study, respectively. Therefore, it provided the water release profile that was the most similar to that of native vernix. Figure 2 presents water release