Menthyl Lactate Worst Irritant No known benefits Menthyl Lactate description The ester of menthol and lactic acid, this ingredient is used as a cooling or flavoring agent and fragrance in cosmetics. This derivative of menthol is supposed to be less sensitising than menthol, but there’s no substantiated, pubsliehd research supporting this notion. Menthyl lactate may be synthetic, plant-derived, or animal-derived. Related ingredients: Menthol