Isododecane

Isododecane is a volatile hydrocarbon solvent/emollient commonly used at moderate-to-high levels in long-wear makeup and sunscreens, and it is generally considered non-sensitizing with low irritation rates in standard patch testing. However, in very sensitive or eczematous skin it can contribute to barrier dryness and stinging indirectly (especially when combined with other volatile solvents/film formers), so I do not score it as completely inert for compromised skin. Safety Notes: In commercial skincare and hybrid makeup-skincare products, isododecane appears at very low levels (~0.1–1%) as a slip/volatile spreading aid in emulsions and sunscreens where it is not the primary solvent. At the high end, consumer-available anhydrous, fast-dry/transfer-resistant formats (e.g., long-wear complexion products, lip/blemish concealers, water-resistant sunscreens and film-former resin systems) can use isododecane as the dominant carrier solvent, commonly 40–70% and observed up to ~90% in extreme anhydrous systems. It is primarily a leave-on volatile hydrocarbon; rinse-off use exists but is typically lower due to limited benefit and processing/solubilization needs.