502 JOURNAL OF COSMETIC SCIENCE BASIC SKIN EVALUATION METHODS R. Randall Wickett, Ph.D. Universit3, of Cincinnati, College of Pharmacy Non-invasive biophysical or bioengineering methods have proven of great value in both understanding how products affect the skin and for claim support purposes. Some of the most common non-invasive methods to evaluate skin function will be reviewed in this presentation along with common protocols that incorporate skin bioengineefing instruments. TEWL Transepidermal water loss measurements can be used to quantify the effects of products on the barrier function of the skin. TEWL has proven very useful in cosmetic science for studies of surfactant damage to skin. The commonly used instruments rely on the principle first describe by Nilson. 'Relative humidity and temperature are measured at two points above the skin surface and TEWL is calculated from Fick's law. There are published guidelines for TEWL measurements 2. TEWL measurements are often used in the Forearm Controlled Application Test for soap and surfactant products and milder soaps consistently produce less elevation in TEWL. Three mild synthetic detergent bars and pure soap bar, known to be harsh and a mild soap bar with added humectant and water were compared in an FCAT The soap bar caused a significantly higher increase in TEWL compared to the other bars 4. Electrical Measurements on Skin Measurements of skin impedance or reactance (capacitance) are commonly used to estimate the moisture content of skin and for moisturizing claims after one or a few treatments. 5ø, We have investigated the effects of the products salt and glycerin content on these measurements with the three most commonly used commercial instruments 7 We also performed a study testing the ability of measurements 1 hr. after a single application to predict the results of a two week moisturizer testL Correlations betweens between I hr measurements and grade improvement after one week of treatment were significant for all three instruments. Mechanical Measurements T•vo commonly used instruments are the Dermal Torque Meter©(DTM) or T•vistometer • and the Cutometer© 'ø. We have investigated the effects of hydration on Cutometer measurements •' and compared the Cutometer to the DTM for assessing the effect of moisturizer treatment dry leg skin t2. The DTM was somewhat more sensitive than the Cutometer for this purpose. Sensitivity of the Cutometer to moisturizer treatment can be improved by using 200 mbar of negative pressure compared to 500 mbar?. Contact pressure can have a significant effect on mechanical measurements and needs to be controlled carefully. Skin pH Skin pH is a parameter that is easy to measure but not always so easy to interpret. Skin has an "acid mantle" with apparent pH values running between 4.0 and 6.0 for 95% of the populationY Soap washing causes an increase in pH which decreases with time due the innate buffering capacity of human skin•L D-Squames, Adhesive Disks. D-Squame© adhesive disks are a useful means to quantify skin scaling? • We have used D-Squames to investigate scaling in skin from Black and White subjects. '• While grades were generally higher in Black subjects the desquamation index of D- Squames from White subjects was as high or higher than from Black subjects. We hypothesize that grades of skin scaling are anomalously high from Black subjects because the scales show more clearly against the darker skin background.

2004 ANNUAL SCIENTIFIC SEMINAR 503 Chromameter Measurements of Erythema The Minolta Chromameter © measures color on the L,a*b* scale. L is the brightness from 0 to 100, a* is red/green with +60 for pure red and -60 for green, b* is blue yellow with +60 for pure yellow and -60 fbr pure blue. The redness of an object can be investigated by measure a*. In the FCAT discussed above a* was increased significantly more from treatment with the harsh soap bar and correlated well with visual grades of erythema5 Sebutape and Subumeter Sebutape© is an opaque micro-porous hydrophobic polymer film. When placed on the skin sebum flows into the pores making transparent spots. Good quantitative agreement between sebum production measured by hcxane extraction of the skin and Sebutape collection has been reported. '9 Image analysis can be used to determine the number of active sebaceous follicles and estimate sebum production. The Sebumeter© uses a similar principle with an optical sensing system and is a convenient way to measure sebum output. Reference List 1. Hammarlund K, Nilson P, Oberg PA, Sedin G: Transepicermal water loss in newborn infants: I. Relation to ambient humidity and site of measurement and estimation of total transepidermal water loss. Acta Paediatr Scand 66: 553, 1977. 2. Pinnagoda J, Tupker RA, Agner T, Setup J: Guidelines fbr transepidermal water loss (TEWL) measurement. A report from the Standardization Group of the European Society of Contact Dermat•tis. Contact Dermatitis 22:164-178, 1990. 3. Ertel KD, Kesw•ck BH, Bryant PB: A torearm controlled application technique for estimating the relative mildness of personal cleansing products. J Soc Cosmet Chem 46: 67-76, 1995. 4. Wickett RR: Forearm wash testing of mild soap bars containing collmdal oatmeal. Candian Chemical News 49: 22-23, 1997. 5. Berardesca E: EEMCO guidance for the assessment of stratum corneum hydration: electrical methods. Skin Res Technol 3: 126-132, 1997. 6. Loden M, Lindberg M: The influence of a single application of different moisturizers on the skin capacitance. Acta Derm Venereol 71: 79-82, 1991. 7. Li F, Visscher M, Conroy E, Wickett RR: The ability of electrical measurements to predict skin moisturization I. Eftkcts of salt and glycerin on short-term measurements. J Cosmetic Science 52: 13-22, 2001. 8. Li F, Visscher M, Conroy E, Wickett RR: The ability of electrical measurements to predict skin mmstunzation 11. Correlations between one hour measurements and long term results. J Cosmetic Science 52: 23-33, 2001. 9. Agache PG: Twistometry measurement of skin elasticity, in Serup J, Jemec GBE (eds), Handbook of Non-invasive Methods and the Skin, Ann Arbor, CRC Press, 1995, 319-334. 10. Courage W: Hardware and measuring principle: corneometer, in P. Elsner EBaHIM (ed), Bioengineering of the skin: Water and the Stratum Corneum, Boca Raton, CRC Press, Inc., 1994, 171-175. 11. Murray BC, Wickett RR: Sensitivity of cutometer data to stratum corneum hydration level. Skin Research and Technology 2: 167-172, 1996. 12. Murray BC, Wickett RR: Correlanons between Dermal Torque Meter, Cutometer and Derreal Phase Meter measurements of human skin. Skin Research and Technology 3: 101-106, 1997. 13. Wickett RR: Stretching the Skin Surface: Skin Elastmity. Cosmetics and Toiletries 116: 47-54, 2001. 14. Dikstein S, Zlotogorski A: Skin Surface Hydrogen Ion Concentration (pH), in Leveque JL (ed), Cutaneous Investigation •n Health and Disease, New York, Marcel Dekker, 1989, 59-78. 15. TrobaughC.M., Wickett RR: Personal Care Products: Effects on Skin Surface pH. Cosmetics and Toiletries 105: 41-46, 1990. 16. Schatz H, Kligman AM, Manning S, Stoudemayer T: Quantification of dry(xerotic) skin by image analysis of scales removed by adhesive disks (D-Squames). l Soc Cosmet Chem 44: 53-63, 1993. 17. Schatz H, Altmeyer PJ, Kligman AM: Dry Skin and Scaling Evaluated by D-Squames and Image Analysis, in Serup J, Jcmec GBE (eds), Handbook of Non-Invasive Methods and the Skin, Ann Arbor, CRC Press, 1995, 153-157. 18. Wartier AG, Khgman AM, Harper RA, Bowman J, Wicket RR: A comparison of black and white skin using noninvasive methods. J Soc Cosmet Chem 47: 229-240, 1996. 19. Kligman AM, Miller DL, McGinley Kj: Sebutape: A device for visualizing and measunng human sebaceous secretion. J Soc Cosmet Chem 37: 369-374, 1986.