Trihydroxystearin

Trihydroxystearin is a fatty acid derivative used primarily as a structuring/thickening and stabilizing agent in creams and sticks, typically at low single‑digit percentages. It is not an active and has a low inherent irritancy profile in standard patch testing, with reactions more consistent with rare individual sensitivity or formulation-related occlusion rather than direct chemical irritation. For highly reactive or eczema-prone skin, I score it as very gentle (not fully inert) to reflect the small but real risk of intolerance in compromised barriers. Safety Notes: Trihydroxystearin is most often used as a structuring/thickening and gellant for oils in emulsions, balms, sticks, and sunscreens; in many mass-market leave-on lotions/creams it appears at low “processing aid” levels around ~0.05–0.3% to tune viscosity and stability. In anhydrous systems (lip balms, cleansing balms, pomades) and high-structure formats (sticks/solid balms), consumer products commonly use ~1–3% and can reach about ~5% where a firm gel network and high payoff are desired. It is not specifically concentration-restricted by major cosmetic regulations, so the upper end is driven mainly by aesthetics, crystallization/texture control, and processing limits rather than legal caps.