For hundreds of years, cascara sagrada has been a natural herb used to support healthy bowel function. Made from the bark of the California buckthorn, a tree found in the northwestern U.S., records of cascara sagrada date back to the 1800s when it was used by Native American tribes and Spanish and Mexican priests as a natural laxative. Used as a stimulant laxative, it works by causing muscle contractions in the intestines and helps move stool through bowels.