Relationships between skin properties and environmental parameters

Background/purpose: Many authors have written about skin physiological parameters and their changes according to different environmental conditions. Nevertheless, the literature puts in evidence disagreement among different studies due to the great variability in these parameters and due to the difficulty in comparing the results obtained under different working conditions. Hence, the aim of this work is to attempt to clarify the relationship between some skin properties, such as transepidermal water loss (TEWL), skin hydration and mean skin temperature (T_sk), and the environmental parameters of ambient temperature (T_a) and relative humidity (RH), with the help of a climatic chamber to make the environment reliable. This work must be considered as the preliminary step of a wider project dealing with textile engineering: the results will be used in identifying criteria for textile design with the aim of producing more comfortable clothing. Methods: Experiments were carried out in a climatic chamber with independently controlled T_a and RH. All the combinations between three levels of T_a (20°C, 25°C and 30°C) and four levels of RH (25%, 45%, 65% and 85%) were used on a panel of six young female subjects. The assessments made were: skin surface hydration using an electrical capacitance method, TEWL using a Tewameter and T_sk using a set of thermistors. Results: The results showed a significant correlation between TEWL and T_a, while the RH had a weaker effect on TEWL in the temperature range under investigation. Also, T_sk showed a higher correlation with T_a compared with RH. Finally, skin surface hydration was found to be strongly affected by both environmental parameters. Conclusions: The analysis of experimental data resulted in the elaboration of some easy empirical models useful to evaluate the changes in TEWL, skin hydration and T_sk in different climatic conditions. These relationships must be considered to be valid only in a restricted range of T_a (20–30°C) and RH (25–85%) for young female subjects (25–35 years old).