Assafras is a perennial tree native to Eastern United States. Native Americans used infusions made from the root bark as a remedy to treat fevers, diarrhea, and rheumatism. Sassafras was even used as a flavoring for root beer decades ago. However, sassafras contains safrole, a volatile oil, which has been classified as a likely carcinogen to humans, and banned as a food additive by the FDA.