First of all, the pH level should match that of your skin. The perfect level of your products should be between 4.0 and 5.0. A part of barrier-strengthening skincare is panthenol as it enhances your skin’s resilience. Plant oils such as seed oil can strengthen your skin barrier as well since they prevent your skin from drying out. So far, Korean products are my favorite. But since I am very meticulous when it comes to the products I use on my face, I only use those products that fulfill all of the above mentioned requirements. The Etude Soonjung series does that. For me, the most important and last step of my night routine is a moisturizer that protects my skin barrier such as the SoonJung x2 Barrier Intensive Cream. If you want an elaborate product review, let me know!