SC WATER-HANDLING PROPERTIES 291 charge to potential on an electrically charged isolated conductor) under occlusion to determine the extent of skin hydration (17). Transepidermal water accumulates under the sensor for twenty seconds, and the value is calculated as the slope of the regression line (cru/sec). The MAT methodology provides a dynamic measure of SC water-handling ability, as previously reported (18). NATURAL MOISTURIZING FACTOR AND VEHICLE FORMULATIONS The NMF components (Table I) were added to a vehicle of hydroxyethyl cellulose (Natrosol) in distilled water, and the viscosity was adjusted to 300 cps to produce a formulation suitable for application to the skin. The formula was based on reported compositions of NMF (14,19,20). The levels of pyrrolidone carboxylic acid (PCA), urea, citrate, chloride, and total amino acids were taken from the NMF composition reported by Cler and Fourtanier (19). The relative ratios of neutral, basic, and acidic amino acids were formulated to match the composition of amino acids extracted from the skin after treatment with acetone/ether followed by a water soak (14). The relative amounts of the neutral amino acids approximated the ratios found in guinea pig epidermis (20). The formula pH was 5.6. A vehicle control was prepared in a similar fashion and adjusted to a viscosity of 300 cps and a pH of 5.6. SITES AND INITIAL MEASUREMENTS Six 2 x 2-cm treatment sites areas were marked on each volar forearm. The areas were randomized for left versus right and for position along the arm, and treatments were assigned as shown in Table II. Prior to entry into the study, subjects refrained from using a moisturizer on their volar forearms for 72 hours. Measurements were performed after Table I Natural Moisturizing Formulation Percent ITIg/ClTI 2 Component (% by wt) applied to site Pyrrolidone carboxylic acid 12 0.24 Urea 7 0.14 Sodium chloride 5 0.10 Sodium lactate 5 0.10 Potassium citrate 0.5 0.01 Serine 18.2 0.36 Glycine 9.1 0.18 Arganine 3.2 0.064 Glutzunic acid 2.3 0.04 Tyrosine 0.5 0.01 Alanine 6.6 0.13 Hydroxyethyl cellulose • Deionized water 2 1 Sufficient quantity to provide a viscosity of 300 cps. 2 Added as necessary to provide a total of 100% by weight. The natural moisturizing factor components were added to a vehicle of hydroxyethyl cellulose and the viscosity was adjusted to 300 cps for application to the skin. The formula was based on reported compo- sitions of NMF (14,19,20).

292 JOURNAL OF COSMETIC SCIENCE Table II Skin Treatments Site Arm A Site Arm B 1 Untreated 7 Soak 2 Untreated + vehicle 8 Soak + vehicle 3 Untreated + NMF 9 Soak + NMF 4 Acetone/ether extraction (A/E) 10 A/E + soak 5 A/E + vehicle 11 A/E + soak + vehicle 6 A/E + NMF 12 A/E + soak + NMF The twelve 2 x 2-cm treatment sites were randomized for lefk vs right and for position along the arm. Both arms were extracted with acetone/ether as shown. One arm was then soaked in water for ten minutes. The other arm served as the control. Following the soak procedure, the NMF formulation was applied to the specified sites. Soak indicates water soak, and vehicle indicates the hydroxyethyl cellulose-containing control for the NMF formulation. equilibration to environmental conditions (temperature 21 o + 1øC and relative humidity 31 + 5%) for 30 minutes. Baseline skin measurements of TEWL, skin hydration, and MAT were made for each of the twelve treatment sites (time = 0 min). ACETONE/ETHER EXTRACTION Three sites on each forearm (six total) were treated with a 1:1 mixture of acetone/ether (A/E) to remove surface lipids and intercellular lipids from the outer SC layers. The acetone/ether extraction procedure was expected to remove only very small quantities of water-soluble materials from the skin (21). The sites were exposed to A/E for five minutes using a glass extraction cup to hold the solvent. The areas were then wiped repeatedly with cotton pads dipped in the A/E mixture. This process was continued until the TEWL reading increased to approximately 2 x the baseline value. Following extrac- tion, the biophysical measurements were repeated for each of the six sites. SOAKING Once the A/E extraction was complete, one forearm was soaked in fresh water (tem- perature 40 ø + 1.4øC) for ten minutes and blotted dry. The sites on the other (unsoaked) forearm served as control sites. Fifteen minutes after soaking, the biophysical measure- ments were repeated for all 12 sites, including the untreated control site. NMF AND VEHICLE TREATMENT The NMF formulation was applied (2 mg/cm 2) to four sites immediately following the post-soak measurements: untreated (no extraction, no soak), A/E-treated, soaked, and A/E plus soak. The vehicle control (2 mg/cm 2) was applied to another set of sites (untreated, A/E-treated, soaked, A/E plus soak). The biophysical measurements were made 30 minutes after application for all 12 sites (Table II), including the untreated control site. The test areas were left undisturbed for 3.5 hours. The subjects returned to the test facility and the measurements were made following the 30-minute equilibra- tion.