C9-12 Alkane

C9-12 Alkane is a lightweight emollient/solvent (often used as an isododecane-like hydrocarbon) typically included at a few percent up to higher levels in makeup and leave-on formulations to improve slip and reduce greasiness. As a nonpolar, nonreactive hydrocarbon, it has very low inherent irritancy in patch testing and clinical use, with reactions being uncommon and more often related to overall formula factors (occlusion, co-ingredients, or impaired barrier) rather than the alkane itself. Given the need to protect highly reactive/compromised skin while acknowledging rare intolerance, it fits best as exceptionally gentle rather than completely inert. Safety Notes: In commercial products, C9-12 Alkane commonly appears at low levels (~0.1–2%) as a slip/feel modifier or light emollient in emulsions (e.g., lotions, sunscreens, serums), including both leave-on and rinse-off formats. At the high end, it is sold OTC as the primary/near-neat base in anhydrous facial oils, makeup primers, and silicone-free “dry oil”/emollient concentrates where it can comprise the bulk of the formula (often 60–95% and occasionally approaching ~99% in very minimal-ingredient blends). There is no specific FDA/EU concentration cap for this cosmetic emollient; practical limits are driven by product form (emulsion vs anhydrous) and desired sensorial properties.