22 JOURNAL OF COSMETIC SCIENCE (2) (3) (4) (5) (6) (7) (8) (9) (lO) (11) (12) (13) (14) (15) (16) B. Idson, Water and skin, J. Soc. Cosmet. Chem., 24, 197-212 (1973). H. Tagami, M. Ohi, K. Iwhtsuki, Y. Kanamaru, M. Yamada, and B. Ichijo, Evaluation of the skin surface hydradon in vivo by electrical measurements,J. Invest. Dermatol., 75, 500 (1980). R. R. Warner and N. A. Lilly, "Correlation of Water Content with Ultrastructure in the Stratum Corneun," in Bioengineering of the Skin: Water and the Stratum Corneum, P. Elsnet, E. Berardesca, and H. I. Maibach, Eds. (CRC Press, Boca Raton, FL, 1994), pp. 3-12. E. Berardesca, EEMCO guidance for the assessment of stratum comeurn hydradon: Electrical methods, Skin Res. Technol, 3, 126-132 (1997). E.J. Clar, C. P. Her, and G. Sturelle, Skin impedance and moismrization, J. Soc. Cosmet. Chem., 26, 337-353 (1975). D.C. Salter, Instrumental methods of assessing skin moisturization, Cosmet. Toiletr., 102, 103 (1987). S. Oilmar, A. Eek, F. Sundstrom, and L. Emtestam, Electrical impedance for estimation of irritation in oral mucosa and skin, Med. Prog. Technol., 21, 29-37 (1995). R.O. Potts, Stratum corneum hydradon: Experimental techniques and interpretations of results, J. Soc. Cosmet. Chem, 37, 9-33 (1986). J. Fluhr, M. Gloor, S. Lazzerini, P. Kleesz, R. Grieshaber, and E. Berardesca, Comparative study of five instruments measuring stratum comeurn hydradon (Corneometer CM 820 and CM 825, Skicon 200, Nova DPM 9003, DermLab). Part I. In vitro, Skin Res. Technol., 5, 161-170 (1999). P. Clarys, A. O. Barel, and B. Gabard, Non-invasive electrical measurements for the evaluation of the hydradon state of the skin: Comparison between three conventional instruments--the Corneometer, the Skicon, and the Nova DPM, Skin Res. Technol., 5, 14-20 (1999). W. Courage, "Hardware and Measuring Principle: Corneometer," in Bioengineering of the Skin: Water and the Stratum Corneum, P. Eisner, E. Berardesca, and H. I. Maibach, Eds. (CRC Press, Boca Raton, FL, 1994), pp. 171-175. H. Tagami, "Hardware and Measuring Principle: Skin Conductance," in Bioengineering of the Skin: Water and the Stratum Corneum, P. Elsnet, E. Berardesca, and H. I. Maibach, Eds. (CRC Press, Boca Raton, FL, 1994), pp. 197-203. B. Gabard and P. Treffel, "Hardware and Measuring Principle: The Nova DPM 9003," in Bioengineering of the Skin: Water and the Stratum Corneum, P. Elsher, E. Berardesca, and H.I. Maibach, Eds. (CRC Press, Boca Raton, FL, 1994), pp. 177-195. M.D. Bart, W. B. Davis, W. A. Gerrard, and B. D. Ridge, Changes in the physical properties of the stratum corneum following treatment with glycerol,J. Soc. Cosmet. Chem., 39, 367 (1988). D. L. Bissett and J. F. McBride, Skin conditioning with glycerol, J. Soc. Cosmet. Chem., 39, 367-381 (1988).

Cosmet. Sci., 52, 23-33 (January/February 2001) The ability of electrical measurements to predict skin moisturization. II. Correlation between one-hour measurements and IonD-term results FANG LI, EILEEN CONROY, MARTY VISSCHER, and R. RANDALL WICKETT, College of Pharmacy, University of Cincinnati (F. L., E.C., R.R.W.), and The Skin Sciences Institute, Children's Hospital Medical Center (M.V.), Cincinnati, OH 45267. Accepted for publication January 15, 2001. Synopsis We investigated the ability of short-term (one-hour) electrical measurements with three different commonly used instruments to predict the effects of long-term treatment with glycerin-containing formulations on moderately dry leg skin. We report the moisturizing effects of glycerin on healthy female adult skin in a two-week study as measured by electrical conductance and capacitance, transepidermal water loss (TEWL), and clinical grading of skin dryness. The test formulations contained 1.5% NaC1 and levels of glycerin from 0% to 15 %. Results obtained with a smaller cohort of ten subjects, one hour after treatment, were predictive of moisturizing efficacy in the two-week period among twenty subjects with dry leg skin. Our results show that single application tests can be predictive of longer-term results with humectant-based moisturizers and that electrical measurements of skin conditions correlate well with skin grades. INTRODUCTION Use of non-invasive electrical instruments to determine skin hydration has become widely accepted (1-4). The reliability of commercial instruments for electrical measure- ments and the correlation of these methods with each other have been investigated (5,6). Bart eta/. (16) found that long-term application of glycerin resulted in improved skin condition as measured by reduced electrical impedance, reduced transepidermal water loss, increased coefficient of friction, increased skin smoothness. They explained the phenomenon by assuming that glycerol interacts with stratum comeurn lipid structures or proteins, altering their water-binding and/or hydrophilic properties, and therefore changing the status of water in the outer layers of the SC. In Part I of this study, we showed a strong linear relationship with electrical response and glycerin concentration in a two-hour, single-application test using three different commercial instruments. We also reported that salt in the formulation can significantly affect the electrical device readings and that the salt effect is dependent on glycerin concentration. 23