3.5. Transepidermal Water Loss (TEWL), Skin Hydration, and Skin pH Measurements

The TEWL, skin pH, and skin hydration measurements were conducted using TEWAmeter TM 300 probe, skin pHmeter PH950, and Corneometer CM825 probe connected to a MPA adapter (Courage + Khazaka Electronic, Köln, Germany), respectively. This study was conducted on 10 volunteers, according to the procedure described by Nizioł-Łukaszewska et al. [63]. The areas (2 × 2 cm in size) were marked on the forearm skin of volunteers. Then, 0.2 mL of the cosmetic was applied to 3 fields. One field (control field) was not treated with any sample. The sample solutions were gently spread over every skin fragment in the marked area and, after 20 min, dried with a paper towel. After 1 h and 5 h, the hydration, TEWL, and skin pH measurements were taken. The final result was the arithmetic mean (from each volunteer) of 5 independent measurements (skin hydration and pH) and 20 measurements (TEWL).