Isohexadecane

Isohexadecane is an inert, nonpolar emollient/solvent used in leave-on and makeup products typically at a few percent up to higher levels, and it is generally well tolerated in patch testing with low rates of irritation. It does not have the pH-dependent reactivity or barrier-disrupting profile seen with strong actives, though very reactive or eczema-prone skin can occasionally sting from occlusion or product context. Given its broad clinical tolerability but acknowledging rare reactivity in compromised skin, I score it as exceptionally gentle rather than completely inert. Safety Notes: Isohexadecane is used as a volatile/light emollient and slip agent, and in many creams/lotions/cleansers it appears at low supporting levels (~0.1–3%) to improve spreadability and reduce greasiness. In long-wear color cosmetics and makeup-remover/balm-to-oil cleansers, it commonly rises into the 5–30% range as a key sensory solvent/emollient. The highest consumer-available levels are seen in anhydrous makeup removers, cleansing oils, and silicone-free primer/serum-oil textures where isohexadecane can be the dominant carrier phase, reaching ~60–85% in real-world OTC products (typically leave-on makeup/primers or rinse-off removers/cleansers).