Castor Oil What Is Castor Oil? Castor oil is a vegetable oil produced by pressing the seeds of the castor plant (Ricinus communis). In terms of composition, castor oil is a triglyceride fatty acid and nearly 90% of its fatty acid substance is ricinoleic acid, an unsaturated omega-9 fatty acid. Other vital components include oleic acid and linoleic acid. https://www.nationalnutrition.ca/aromatherapy-essential-oils/base-oils/castor-oil.html #CastorOil