Skin barrier cross-section Cross-section of the skin on a hospitality worker's hand: skin cells (bricks) sealed by lipid mortar. Cleaning-chemical spray, water and gloves strip the mortar, moisture escapes and irritants get in. SURFACE · BACK OF THE HAND · BACK OF HOUSE PHASE 1 · HEALTHY CROSS-SECTION, NOT TO SCALE Stratum corneum 10–20 layers of flat, dead cells.Your outer barrier. Lipid “mortar” Ceramides, cholesterol, fatty acidsseal the gaps between the bricks. Living epidermis Makes new cells that move up andflatten over about 4 weeks. Dermis Collagen and blood vessels. LEGEND Water Irritants Cleaning chemical

Brick-and-mortar model of the stratum corneum: Elias PM, J Invest Dermatol 1983;80:44s–49s. Exposure: R&R Lotion blog, Protecting Your Skin with Barrier Creams (2023). Illustration for education only.