Thiotaurine

Thiotaurine is an antioxidant/osmoprotective sulfur-containing amino-acid derivative typically used at low concentrations (about 0.1–1%) to help mitigate oxidative stress, and it is not a pH-dependent exfoliating active. Available safety use data and its close structural similarity to well-tolerated endogenous osmolytes suggest a low inherent irritancy profile, with only occasional stinging possible on severely compromised barriers. Given the limited breadth of large-scale patch-test data in highly reactive eczema populations, I score it as very gentle rather than exceptionally gentle for patient safety. Safety Notes: In commercial skincare, thiotaurine is most often used as an anti-pollution/antioxidant active at low tenths of a percent; I have observed it at ~0.01% in multi-ingredient antioxidant/soothing serums where it functions as a minor supportive active. Higher-strength consumer leave-on products (serums/ampoules/eye gels marketed for anti-stress/anti-pollution or blue-light defense) have been marketed around 1–2%, with ~2% representing the upper end typically seen before solubility, cost, and overall formula osmolality/skin feel become limiting; rinse-off use is less common and generally trends toward the lower end.