I can use herbal medicine to illustrate. Western medicine is grounded in medical research. New drugs undergo rigorous testing and must be approved by the Federal Drug Administration. To be approved, they need to demonstrate that they do what they claim to do. They also need to show that they do not have serious negative side effects.
Herbal medicines come out of a folk tradition.
Some have been used for centuries but many of the claims associated with them have never been subjected to careful evaluation. Twelve billion dollars are now spent annually in the US on these dietary supplements. Claims are made that have no documented support and, in some cases, they prove harmful. A woman in Louisiana drank a herbal tea that contained a great deal of senna, which is a laxative. It led her to suffer a seizure and permanent heart damage.