Dr. Cass wrote several books on the use of oregano and I am sure he doesn't know half what the Amish Clinic has discovered. Spices were the ancients method of medicine as well as method of money, oregano being one powerful spice when you have the real thing. Sadly the commercial market believes the public can't handle pure essential oils and they must play it on the safe side, so they dilute oils and in doing so they get very greedy, so the essential il trade is not one always trusted, David Christopher states most in the USA are fake or partly fake, they teach a course on the use of essential oils and I did not take it.