Taurine

Taurine is an amino sulfonic acid used primarily as a humectant/osmolyte and skin-conditioning agent, typically at low concentrations (about 0.1–2%). Available human data and real-world cosmetic use suggest it is generally well tolerated and not a common irritant or sensitizer, especially compared with surfactants, acids, or fragrances. While reactions are still possible in severely compromised barriers, its overall irritation potential in leave-on products is very low, supporting a very gentle score. Safety Notes: In commercial skincare, taurine is most often used as a minor “cell energy/anti-fatigue/osmolyte” active in leave-on serums, eye products, and moisturizers at low doses around 0.01–0.1%, especially when positioned as a supporting ingredient in complex blends. Higher-strength consumer-available formulations (typically water-based leave-on ampoules/serums or concentrated booster-style products) have been marketed in the ~1–3% range, with a small number of niche/high-strength OTC products pushing up to about 5% where solubility and sensory limits still permit. Taurine is not specifically restricted by major cosmetic regulations (EU/FDA) at typical use levels, so the upper bound is driven mainly by formulation practicality and product aesthetics rather than a formal regulatory maximum.