Skin barrier cross-section Cross-section of the skin on a lab worker's hand: skin cells (bricks) sealed by lipid mortar. Sweat trapped under two gloves, plus washing and sanitizing at every glove change, strip the mortar; moisture escapes and irritants get in. SURFACE · BACK OF THE HAND · UNDER TWO GLOVES 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 Inner glove Outer glove

Brick-and-mortar model of the stratum corneum: Elias PM, J Invest Dermatol 1983;80:44s–49s. Exposure: R&R Lotion blog, Double Gloving: Protecting Workers and Environments in Various Industries (2023). Illustration for education only.