Hydrogenated Polydecene

Hydrogenated Polydecene is an inert, highly refined synthetic hydrocarbon emollient used to reduce transepidermal water loss and improve slip, typically in leave-on products at several percent up to higher levels. In clinical use it is generally well-tolerated with a very low rate of irritation or sensitization because it is non-reactive and not a fragrance or preservative. I score it 0.1 (not 0.0) to reflect rare but possible intolerance in severely compromised or eczema-prone skin from occlusion or formulation context rather than intrinsic irritancy. Safety Notes: Hydrogenated polydecene is used at very low levels (~0.1–1%) as a slip/emolliency booster and solvent for lipophilic actives in serums, lotions, and some rinse-off cleansers. In anhydrous leave-on formats (facial oils, oil-serums, balms, hair oils/shine products) it can be a primary emollient/hydrocarbon substitute, commonly 20–70% and in some minimalist single-phase products reaching ~80–90% as the main carrier. It is not subject to a specific EU/FDA maximum for cosmetics, so the upper end is largely driven by sensorial goals, viscosity grade, and compatibility with the rest of the oil phase.