Sodium Carboxymethyl Starch

Sodium carboxymethyl starch is a modified polysaccharide used primarily as a thickener/absorbent in leave-on and rinse-off products, typically at low single-digit percentages. Available safety and patch-test experience with similar carbohydrate polymers suggests very low intrinsic irritation and minimal sensitization risk, but rare reactivity can occur in highly compromised eczema skin due to barrier disruption and product matrix effects. Given it is not truly inert yet is generally well-tolerated, it fits a very gentle (0.2) rating for most sensitive-skin use. Safety Notes: In commercial skincare, sodium carboxymethyl starch is most often used as a secondary thickener/texture modifier and suspension aid at low levels (~0.05–0.5%) in serums, lotions, and cleansers, where it fine-tunes slip and stabilizes dispersed phases. Higher-use levels (~2–8%) are observed in consumer-available high-solids gel-creams, matte/blur primers, and some powder-to-cream or styling/setting-type skincare hybrids where it functions as a primary rheology builder and oil-absorbing structurant. It is used in both leave-on and rinse-off products, with the highest levels more common in leave-on texture-focused formats; no specific EU/FDA cosmetic concentration cap is generally applied beyond safety substantiation and performance/stability constraints.