## 2 Materials and Methods  
The study was approved by the Ethics Committee of the University of Regensburg (21-2481-101, 28 July 2021). A total of 20 subjects (6 women, 14 men) were recruited from the investigator's circle of acquaintances to carry out the study, all of whom had given their written consent. In addition, the following inclusion criteria had to be met: subjects had to be of legal age,capable of giving informed consent, subjects were not allowed to be pregnant, they were not allowed to have any skin diseases or pronounced skin nevi in the study area, and were not allowed to be currently undergoing any topical skin therapy. For each subject, a randomized order of application of 23 (+1 control site) different wound dressings was determined on the back of the subjects (Figure 1). An online randomization tool was used to generate the randomization of the distribution (between 2021 and 2024). The randomization was intended to ensure that any measurement differences could not be associated with different locations on the skin. A total of 23 different wound dressings were examined. One area of skin was omitted. This served as a control condition. The wound dressings used belong to different wound-dressing categories (Table 1). Three different types of simple dressings were examined (Gazin(r) gauze dressings, Solvaline(r)N, Metallicine(r) dressings, each from Lohmann & Rauscher, Rengsdorf, Germany). A total of 7 wound dressings can be assigned to the foam-dressing category (Allevyn non-adhesive foam dressing, Allevyn thin foam dressing from Smith+Nephew( London, UK); Mepilex, Mepilex Border Flex from Molnycke( Gothenburg, Sweden); Biatain(r) non-adhesive, Biatain(r) Adhesive from Coloplast Professional(r) (Humlebaek, Denmark). Four Lohmann & Rauscher(r) brand film dressings were examined (Suprasorb P non-adhesive, Suprasorb P adhesive, Suprasorb P sensitive border light, and Suprasorb P sensitive non-border). A transparent dressing was also examined: Tegaderm from the brand 3M Healthcare Germany GmbH(r) (Dusseldorf, Germany). As synthetic skin substitutes, Suprathel(r) (1\(\times\) in moist, 1\(\times\) in dry version) from PolyMedics Innovations GmbH(r) (Kirchheim unter Teck, Germany), EpiGARD from Biovision GmbH(r) (Ilmenau, Germany), Xenoderm from Medical Biomaterial Products(r) (Neustadt-Glewe, Germany), and Biobrane from Smith+Nephew(r) were examined. The last wound-dressing category examined was scar plasters, including Mepiform from the Molnycke(r) brand, Cica care from the Smith+Nephew(r) brand and Scar FX from the TRICONmed GmbH(r) brand (Korle, Germany). Figure 1: Shows how the different wound dressings were distributed across the subjects’ backs. The image was generated with [[https://smart.servier.com/](https://smart.servier.com/)]([https://smart.servier.com/](https://smart.servier.com/)) (accessed on 26 August 2024). The data were collected in an air-conditioned and heated room with closed doors and constant air conditions, so as not to interfere with the measurements. Subjects were able to acclimatize to the room conditions prior to the investigations, so as not to impair the measurements. Skin hydration and TEWL were measured at each of 24 skin sites, starting in an area below the neck and extending to the skin above the cocyx, using the Khazaka probes, before applying the corresponding wound dressing. After the baseline measurements, the respective wound dressings were applied. Some of the wound dressings were self-adhesive (e.g., \"Biatain adhesive\"), and others were applied to the skin using adhesive strips attached to the edge (e.g., Solvaline), whereas the wound dressings were only fixed at the borders, in order to not compromise the effects on the underlying skin. Measurements were taken in the skin areas with no adhesive, to exclude a potential impact of tape stripping on the measurements.