From paula’s choice site:
Categories: Miscellaneous, Texture Enhancer
Synthetic hydrocarbon ingredient used as a solvent. Isododecane enhances the spreadability of products and has a weightless feel on skin. All hydrocarbons used in cosmetics help prevent the evaporation of water from skin.
Among its many uses in beauty products, it’s not uncommon to see isododecane in long-wear lipsticks and foundations, where it helps minimize color transfer and lends itself to a lightweight, matte finish.