Propylene Glycol Isostearate

Propylene Glycol Isostearate is an emollient/surfactant (propylene glycol ester of isostearic acid) typically used at low-to-moderate levels in creams, cleansers, and makeup to improve slip and solubilize oils. It is generally well tolerated and not a classic sensitizer, but as a propylene-glycol–derived ester it can still trigger mild irritation or stinging in highly reactive or compromised skin, especially in leave-on products or when combined with other irritants. Given sensitive-skin and eczema populations, I rate it as gentle but not inert. Safety Notes: Propylene Glycol Isostearate is typically used as an emollient/skin-conditioning agent and nonionic co-emulsifier/solubilizer, and in many leave-on creams/lotions it appears at low secondary levels around 0.05–1% to support feel and emulsification. In richer anhydrous or water-in-oil style balms/cleansing creams and some high-slip makeup/skin-prep products, market-observed usage can climb into the mid-to-high single digits, with upper-end consumer formulations reaching ~10–15% when it functions as a primary emollient/texture modifier. No specific FDA/EU maximum concentration limit is generally assigned to this ingredient as a cosmetic, so practical limits are usually set by sensorial impact, compatibility, and irritation potential in leave-on products.