Quote from "The Cure is in The Cupboard" by Dr Cass Ingram:
Oil of wild oregano is the premier natural antiseptic. It posesses vast microbial-killing powers. Every microbe against which it has been tested succumbs to it. Uniquely, there is no known tendency for microbial resistance. It is the premier of all known natural antiseptics. It is such an effective antiseptic that it cannot be matched either in the synthetic or natural arena in terms of its ability to kill a wide range of microbes.