Micellar Water and the Skin Barrier: Comparing Rinsing vs. Non-Rinsing Application

The goal of this clinical trial is to assess how micellar water affects the skin barrier in healthy adult volunteers. The main questions it aims to answer are: * Does leaving micellar water on the skin affect skin barrier function differently than rinsing it off? * Are there measurable differences in transepidermal water loss (TEWL), skin hydration, and erythema between the two application methods? Researchers will compare the effects of micellar water left on the skin versus rinsed off after application. Participants will: * Be randomly assigned to one of two groups * Apply micellar water to their forehead once daily for 21 days * Either leave the micellar water on or rinse it off, depending on their group * Undergo non-invasive measurements of TEWL, skin hydration, and erythema before and after the intervention