The skin barrier, simply explained
By Jeremy Fain, founder of Restelys. Updated 17 October 2026. 2 sources cited.
Everything our care products do revolves around a layer of skin thinner than a sheet of paper. Understanding it explains why skin feels tight, and how to prevent it.
The outermost layer of the skin, the stratum corneum, works like a wall: flattened cells are the bricks, and lipids (ceramides, cholesterol, fatty acids) are the mortar. This wall keeps water in and keeps what comes from outside at a distance.
When the mortar runs thin, water escapes: dermatologists call this transepidermal water loss. The skin becomes dry, rough and tight. Washing too often or too harshly, hard water and dry air are the most common causes.
Hence our three rules: cleanse with gentle bases, add glycerin to hold water, and nourish with emollients close to the skin’s own lipids, such as olive squalane.
Sources
- Proksch E., Brandner J.M., Jensen J.M. “The skin: an indispensable barrier”. Experimental Dermatology, 2008.
- Elias P.M. “Stratum corneum defensive functions: an integrated view”. Journal of Investigative Dermatology, 2005.
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