Hydrogenated Styrene/Isoprene Copolymer

Hydrogenated Styrene/Isoprene Copolymer is an inert, high–molecular weight synthetic film-former/texture agent used at low-to-moderate levels to improve slip, viscosity, and wear, with minimal skin penetration. Clinical experience and patch testing trends for this class of polymers show very low irritation and sensitization potential, though rare mechanical/occlusive discomfort can occur in highly reactive or compromised skin. Given its overall biologic inertness but acknowledging nonzero risk in severely sensitized patients, it aligns best with an exceptionally gentle score rather than absolute inert. Safety Notes: In commercial skincare, Hydrogenated Styrene/Isoprene Copolymer is most often used as an oil-phase rheology modifier/film former in leave-on products (e.g., lotions, creams, sunscreens, primers) where it can appear at very low levels (~0.05–0.3%) as a minor viscosity/texture aid. Typical mainstream use is commonly around ~0.5–5%, while the upper end is observed in high-structure anhydrous or high-oil systems (e.g., balms, stick products, waterless occlusive/primer-like textures) where it can reach ~10–20% to build gel networks, cushion, and water resistance; such high levels are uncommon in rinse-off formats due to sensorial and deposition constraints.