Intra- and inter-individual variations in transepidermal water loss on theface: facial locations for bioengineering studies

The volar forearm is the favored location for bioengineering studies. Howev er, transepidermal water loss (TEWL), which is an important indicator of th e function of the epidermal barrier, shows regional variations, and for the evaluation of cosmetic formulations, facial skin would be more suitable. I n this study, we have compared 10 facial locations with 1 test site on the volar forearm for absolute TEWL values, reproducibility, and correlation. M easurements were performed over 3 consecutive days. The TEWL values of the facial test sites were higher compared to forearm values and did not correl ate 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 super ior to the nervus supraorbitalis, the medial borders of the musculus masset er, and the center of the chin proved to be locations with relatively stabl e TEWL values. There was a greater variability at the center of the forehea d and at the center of the cheeks. It is recommended that TEWL measurements on facial locations with stable TEWL values are used for the evaluation of cosmetic formulations.