Castor oil is most commonly used as a laxative. But castor oil's natural antiviral and antimicrobial properties make it a popular treatment for skin problems known as dermatosis as well as fungal infections. It's also used for hair growth. Castor oil has a number of medicinal, industrial, and pharmaceutical uses. It's commonly used as an additive in foods, medications, and skin care products, as well as an industrial lubricant and biodiesel fuel component.