## 2 Materials and Methods  
Our study was designed as a randomized controlled clinical trial. The study setting was the University of Split, School of Medicine, Department of Pharmacy, and it was conducted in June 2023. The Ethics Committee of the University of Split School of Medicine approved the research, and the study was conducted in accordance with ethical principles. In total, 25 healthy male and female volunteers aged 21 to 29 participated in the research. The subjects had no previously recorded skin diseases. Every participant signed an informed consent before the start of the study. The informed consent form contained information about the aim of the research, the method, and all procedures of its implementation. The exclusion criteria were the following: skin diseases, skin cancers, sun damage in the place intended for examination, use of immunomododulatory medicine, corticosteroids, or antihistamines 30 days before the start of the study, application of emollient cream 3 days before the start of the study, non-compliance with the protocol, excessive exposure to natural or artificial ultraviolet radiation, pregnancy and lactation, history of vitiligo, melasma and other hyperpigmentation or photosensitivity disorders, immunosuppression, and allergy to some of the ingredients of the cream used for the intervention. Before inclusion in the study, participants were also asked if they had ever experienced a side effect from any of the ingredients of the researched cream. The subjects' forearms were chosen as the test site. On each of the forearms, the place was selected where the irritant dermatitis model would be utilized using a 1% (m/m) sodium lauryl sulfate (SLS) solution. After the baseline skin parameters were measured,a volume of 60 \(\upmu\)L of the solution of SLS was applied to a piece of paper and kept under occlusion for twenty-four hours under twelve-millimeter Finn chambers [14]. Participants were reminded that they should avoid contact with moisture within the above-mentioned period. After removing the Finn's chamber, the test site was washed with water, and the skin parameters were measured again. After skin damage was inflicted, a computer program in Excel was used to randomly select which forearm would receive the treatment and which would remain untreated. The treatment used was Rilastil Difesa Crema Sterile (Istituto Ganassini, Milan, Italy), which contains omega-3, omega-6, and omega-9 fatty acids. Additionally, 5 mg/cm\({}^{2}\) of the cream was applied twice daily to the selected forearm with at least an eight-hour interval between applications. On measurement days, the first application of the cream was performed by the examiners immediately after measuring skin parameters. The second application, as well as all applications on non-measurement days, was performed by the subjects themselves according to the given instructions. The last application of the cream before measurement had to be at least twelve hours prior to measurement to ensure the accuracy of the Transepidermal Water Loss (TEWL) measurement. All subjects received one tube of the cream. The cream was weighed before the start and after the completion of the study to confirm adherence to the protocol. Three skin parameters were measured using a non-invasive bioengineering method with the MPA6 device (Courage + Khazaka GmBH, Cologne, Germany), as these parameters were recognized as fundamental for skin barrier assessment. TEWL is an objective measure of the skin barrier, quantified by the amount of water that evaporates through the skin to the external environment [15]. In our study, skin barrier function was determined by measuring TEWL with the Tewameter TM 300 probe (Courage + Khazaka GmBH, Cologne, Germany). The Tewameter(r) TM 300 probe indirectly measures the water diffusion from the stratum corneum by using two pairs of spatially separated sensors (a relative humidity sensor and a thermometer) that are located inside the hollow cylinder.