Root beer is a sweet North American beverage traditionally made using the root bark of the sassafras tree Sassafras albidum or the vine of Smilax ornata (sarsaparilla) as the primary flavor. Root beer is typically but not exclusively non-alcoholic, caffeine-free, sweet, and carbonated. It usually has a thick and foamy head when poured. Since safrole was banned by the U.S. Food and Drug Administration in 1960 due to its carcinogenicity, most commercial root beers have been flavored using artificial sassafras flavoring, but a few use a safrole-free sassafras extract. Major producers include A&W, Barq's, Dad's, Hires, and Mug.