Herbs are effective when taken as teas, essential oils, extracts, ointments, tablets, or other forms. All civilizations have traditions of using herbs to promote healing. Indeed, most of these herbs were the basis of the development of modern drugs.
Herbal medicine is the oldest known form of medicine.
There is literally no culture, ancient or modern, that did not use plants as part of their medical system. Healers have been working with herbs for medicinal and spiritual purposes. Over the centuries the healing properties of plants and herbs has not changed. Ultimately drugs copy the healing properties of herbs. Our primary knowledge of herbs is based upon 'trial and error'.