Oleic acid is a type of fatty acid that's classified as a monounsaturated omega-9 fatty acid. It's a naturally occurring substance found in various animal and vegetable fats and oils. Oleic acid can be found in creams, lotions and facial oils where it helps to lock in moisture and leave skin feeling soft. Oleic acid is also used in cleansing oils to dissolve makeup and impurities and anti-aging products to reduce the appearance of fine lines and wrinkles.