Skin barrier cross-section Cross-section of the skin on a mechanic's knuckle: skin cells (bricks) sealed by lipid mortar. Parts cleaner and degreaser take the grease and brake dust off and the skin's own oils with them; moisture escapes, irritants get in and the skin splits. SURFACE · KNUCKLES · AT THE PARTS WASHER 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 Grease and brake dust Degreaser

Brick-and-mortar model of the stratum corneum: Elias PM, J Invest Dermatol 1983;80:44s–49s. Exposure: R&R Lotion blog, Glove Safety and Compatibility in the Workplace (2022). Illustration for education only.