Sodium Silicate

Sodium silicate is a strongly alkaline inorganic salt (commonly used in detergents/industrial products and as a high-pH builder), and at functional concentrations it can significantly disrupt the skin barrier, causing stinging, irritant contact dermatitis, and even chemical-burn–type reactions on compromised skin. While trace amounts in a well-buffered cosmetic would lower risk, its typical utility is pH elevation/alkalinity, which is inherently incompatible with eczema-prone or sensitized skin. Given its caustic potential and the severe outcomes seen with high-pH exposures, it warrants a very high irritancy score for patient safety. Safety Notes: In consumer skincare, sodium silicate is most often encountered at trace-to-low levels as an alkalinity/pH adjuster or processing aid in rinse-off cleansers, soaps, and some exfoliating masks, with commercial use commonly starting around ~0.05–0.2%. The highest OTC levels are seen in strongly alkaline, rinse-off cleansing/purifying products (e.g., certain deep-clean masks/soaps and specialty high-pH cleansers) where it can reach ~3–5% active sodium silicate; higher levels are generally constrained by high pH, irritation/corrosivity concerns, and destabilization of many cosmetic systems, making leave-on usage typically ≤0.5% and rare at the upper end.