Skin barrier cross-section Cross-section of the skin on a food worker's hand: skin cells (bricks) sealed by lipid mortar. Wash water, cleaners and gloves strip the mortar, moisture escapes and irritants get in. SURFACE · BACK OF THE HAND · ON THE LINE 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 Wash water Cleaner foam

Brick-and-mortar model of the stratum corneum: Elias PM, J Invest Dermatol 1983;80:44s–49s. Wet work and skin: CDC / NIOSH, Skin Exposures and Effects. Illustration for education only.