Can Castor Oil Really Grow Your Hair? The truth about this popular ingredient. Anna EfetovaGetty Images Castor oil is the little ingredient that could. Want to grow your hair longer? How about thicker, shinier, and healthier? Then you’re going to run into someone, somewhere, recommending that you try castor oil. But what are the actual benefits of the popular oil for hair—beyond all the clean beauty hype? To get the facts straight, we talk to Ann Kohatsu, product developer at Ceremonia, and Psyche Terry, founder of “Castor oil is a vegetable oil that comes from seeds of the castor b...