Safrole is an a compound occurring in several spices and essential oils, shown to cause cancer in rats. Safrole and isosafrole have been used as flavourings in foods, but safety concerns have led regulators to restrict or ban them. It is a classic example of a naturally occurring flavour compound that proved unsafe, reminding toxicologists that natural origin does not guarantee safety. Sassafras oil, once a source, is no longer used for flavouring because of its safrole content. It is regulated or banned as a food flavouring in many countries because of its carcinogenic potential.