Bottom line People have used castor oil for thousands of years as a natural treatment for a variety of health issues. It can help relieve constipation and may be used as a natural skin moisturizer and denture treatment. Though many people use castor oil as a treatment for dry or thinning hair, there’s no evidence that castor oil is effective for improving hair health or stimulating hair growth when used on its own. If you’re interested in using castor oil for constipation or any other health condition, talk with your healthcare professional first to determine whether castor oil is safe and appropriate for your specific health needs.