Isostearyl Neopentanoate

Isostearyl neopentanoate is a fatty ester emollient used to improve slip and reduce transepidermal water loss, commonly present at a few percent up to higher levels in creams, sunscreens, and makeup. Available human patch-test and clinical use experience indicate a low incidence of irritation or sensitization, but as a non-volatile lipid it can still sting on severely compromised or fissured eczema skin and can contribute to occlusive intolerance in some reactive patients. Overall it is typically very well tolerated in sensitive-skin routines, warranting a very gentle score rather than inert. Safety Notes: Isostearyl neopentanoate is used as a lightweight emollient/skin-feel modifier and solvent, showing up at trace-to-low levels (~0.1–1%) in serums, sunscreens, and lotions where it mainly improves slip and spread. In richer leave-on creams, makeup/primer-type products, and lip products it is commonly used in the mid single-digits to teens, and in anhydrous balms/oils and high-slip silicone-free emollient concentrates it can be a major phase component, reaching ~20–40% in some consumer OTC products. Rinse-off products typically sit toward the low end because the benefit is transient and cost/foam considerations limit high loading.