Castor Isostearate Succinate Bon Émollient Hydratation Castor Isostearate Succinate at a glance A mix of esters formed by the reaction of castor seed oil, isostearic acid, and succinic acid Functions as a skin conditioning agent According to one supplier, it can also boost SPF in skin care Deemed safe as used in cosmetics Castor Isostearate Succinate description Castor isostearate succinate is a mix of esters formed by the reaction of castor seed oil, isostearic acid, and succinic acid. This ingredient functions as a skin conditioning agent and is primarily used as an emollient or lubricant in hair or lip care products. According to one of its suppliers, it can also help boost SPF in skin care products. In its raw form, castor isostearate succinate is a clear to slightly hazy amber liquid. The independent Cosmetic Ingredient review board has ruled it safe as used in cosmetics. Typical usage levels range from 0.25%–10%, depending on desired formulary characteristics.