Oleic acid is used as an emulsifying agent in foods and topical pharmaceutical formulations. It has also been used as a penetration enhancer in transdermal formulations to improve the bioavailability of poorly water-soluble drugs in tablet formulations and as part of a vehicle in soft gelatin capsules, in topical microemulsion formulations in oral self-emulsifying drug delivery systems in oral mucoadhesive patches and in a metered dose inhaler.