Castor oil is a vegetable oil pressed from castor beans. Castor oil is rich in ricinoleic acid, a monounsaturated fatty acid. The fatty acid acts as a humectant and can moisturize the skin. Humectants retain moisture by preventing water loss through the outer layer of the skin.
This oil also has pain-reducing and anti-inflammatory properties. It can help to treat inflammatory conditions such as rheumatoid arthritis or psoriasis.