Medicinal plants are various plants used in herbalism and thought by some to have medicinal properties. Few plants or their phytochemical constituents have been proven to have medicinal effects by rigorous science or have been approved by regulatory agencies such as the United States Food and Drug Administration or European Food Safety Authority. The articles in this category can be about traditional healing uses of plants, allopathic medicines derived from plants, and pharmacological research results about a plant. Pharmacognosy is the study of medicines derived from natural sources, including plants. The American Society of Pharmacognosy as "the study of the physical, chemical, biochemical and biological properties of drugs, drug substances or potential drugs or drug substances of natural origin as well as the search for new drugs from natural sources."