C<mt,i:i DiTimititi.i. /9W, 40. 243-247 Prinlfd in Di'iutuirk Al! rif;in.'i reserved Copyright © Munksgaard CONTACT DERMATITIS ISSN 0105-1873 Intra- and inter-individual variations in transepidermal water loss on the face: facial locations for bioengineering studies E. ScHNoz, O. Kuss, J. ScHMiTT, T L. DiHPGHN, M. KUHN' AND M . FARTASCH Department of Dermatology. University of Erlangen-Ntirnberg, Germany 'Elida Faberge. Buxtehude The volar forearm is the favored location for bioengineering studies. However, transepidermal water loss (TEWL). which is an important indicator of the function of the epidermal barrier, shows regional variations, and for the evaluation of cosmetic formulations, facial skin would be more suitable. In this study, we have compared 10 facial locations with I test site on the volar forearm for absolute TEWL values, reproducibility and correlation. Measurements were per- formed over 3 consecutive days. The TEWL values of the facial test sites were higher compared to forearm values and did not correlate with the forearm. On the face, there was a good correlation between the values of the right compared to the left side of the face. The sites superior to the nervus supraorbitalis, the medial borders of the musculus massetcr, and the center of the chin proved to be locations with relatively stable TEWL values. There was a greater variability at the center of the forehead and at the center of the cheeks. It is recommended that TEWL measure- ments on facial locations with stable TEWL values are used for the evaluation of cosmetic formu- lations. Key words: reproducibility of TEWL; face; location; bioengineering methods. © Munksgaard. 1999. Accepted for publieatlon 23 December 1998 Transepidermal water loss (TEWL) is a non-invas- ive method, frequently ttsed to assess stratum eorneutn integrity and as an indirect measure of barrier funetion (1). As a helpful complementary tool, TEWL is widely employed for the evaluation of cosmetic formulations, as well as skin moisttir- izers and repairs (2). It also seems to be an accu- rate and sensitive method to detect and quantify skin alterations caused by chemical irritants. Irritation studies and evaluation of cosmetic for- mulations have mainly been performed on differ- ent forearm sites. It is known that, even on the forearm, different regions may have different skin reactivity (3-8). and results obtained by a skin test on I site are not directly applicable to another site. This holds especially for the regional variation in TEWL, which is probably related to varying skin structure, particularly the regional distribution of eccrine sweat glands (1, 4, 5. 8-10). Investigation of differences in TEWL of the face (mappitig) have not been performed systematically. The aim of the investigation was to obtain data on TEWL values in defined anatomical regions of the face. The reproducibility (intra-individual vari- ation) of TEWL values was validated in order to find anatomical sites with stable TEWL values, as assessment of the effect of topically applied cos- metic products on barrier function and skin hy- dration depends on the stability of TEWL. Materials and Methods Panelisls Measuretnents were performed in 11 healthy sub- jects, aged 19 to 53, mean age 33.9 years. 8 female and 3 male, with no history of atopic eczema or other skin diseases. Informed consent was ob- tained from all of them. During the 3-day study, the panelists were not allowed to apply any topical products: facial cleaning could only be performed with water. Study design Measurements were carried out in an air-con- ditioned room (room temperature 2()-22°C, relative