remedy that lowers blood pressure together with prescription medicine that has the same effect. some herbs may amplify the effects of anticoagulants. certain herbs as well as common fruit interfere with cytochrome p450, an enzyme critical to much drug metabolism. in a 2018 study, fda identified active pharmaceutical additives in over 700 of analyzed dietary supplements sold as "herbal", "natural" or "traditional". the undisclosed additives included "unapproved antidepressants and designer steroids", as well as prescription drugs, such as sildenafil or sibutramine. labeling accuracy a 2013 study found that one-third of herbal supplements sampled contained no trace of the herb listed on the label. the study found products adulterated with contaminants or fillers not listed on the label, including potential allergens such as soy, wheat, or black walnut. one bottle labeled as st. john's wort was found to actually contain alexandrian senna, a laxative. researchers at the university of adelaide found in 2014 that almost 20 percent of herbal remedies surveyed were not registered with the therapeutic goods administration, despite this being a condition for their sale. they also found that nearly 60 percent of products surveyed had ingredients that did not match what was on the label. out of 121 products, only 15 had ingredients that matched their tga listing and packaging. in 2015, the new york attorney general issued cease and desist letters to four major u.s. retailers (gnc, target, walgreens, and walmart) who were accused of selling herbal supplements that were mislabeled and potentially dangerous. twenty-four products were tested by dna barcoding as part of the investigation, with all but five containing dna that did not match the product labels. practitioners of herbalism a herbalist gathers the flower heads of arnica montana. in some countries, formalized training and minimum education standards exist for herbalists, although these are not necessarily uniform within or between countries. in australia, for example, the self-regulated status of the profession (as of 2009) resulted in variable standards of training, and numerous loosely formed associations setting different educational standards. one 2009 review concluded that regulation of herbalists in australia was needed to reduce the risk of interaction of herbal medicines with prescription drugs, to implement clinical guidelines and prescription of herbal products, and to assure self-regulation for protection of public health and safety. in the united kingdom, the training of herbalists is done by state-funded universities offering bachelor of science degrees in herbal medicine. in the united states, according to the american herbalist guild, "there is currently no licensing or certification for herbalists in any state that precludes the rights of anyone to use, dispense, or recommend herbs." however, there are u.s. federal restrictions for marketing herbs as cures for medical conditions, or essentially practicing as an unlicensed physician. united states herbalism fraud over the years 2017–2021, the u.s. food and drug administration (fda) issued warning letters to numerous herbalism companies for illegally marketing products under "conditions that cause them to be drugs under section 201(g)(1) of the act , because they are intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease and/or intended to affect the structure or any function of the body" when no such evidence existed. during the covid-19 pandemic, the fda and u.s. federal trade commission issued warnings to several hundred american companies for promoting false claims that herbal products could prevent or treat covid-19 disease. government regulations the world health organization (who), the specialized agency of the united nations (un) that is concerned with international public health, published quality control methods for medicinal plant materials in 1998 to support who member states in establishing quality standards and specifications for herbal materials, within the overall context of quality assurance and control of herbal medicines. in the european union (eu), herbal medicines are regulated under the committee on herbal medicinal products. in the united states, herbal remedies are regulated dietary supplements by the food and drug administration (fda) under current good manufacturing practice (cgmp) policy for dietary supplements. manufacturers of products falling into this category are not required to prove the safety or efficacy of their product so long as they do not make 'medical' claims or imply uses other than as a 'dietary supplement', though the fda may withdraw a product from sale should it prove harmful. canadian regulations are described by the natural and non-prescription health products directorate which requires an eight-digit natural product number or homeopathic medicine number on the label of licensed herbal medicines or dietary supplements. some herbs, such as cannabis and coca, are outright banned in most countries though coca is legal in most of the south american countries where it is grown. the cannabis plant is used as an herbal medicine, and as such is legal in some parts of the world. since 2004, the sales of ephedra as a dietary supplement is prohibited in the united states by the fda, and subject to schedule iii restrictions in the united kingdom. scientific criticism herbalism has been criticized as a potential "minefield" of unreliable product quality, safety hazards, and potential for misleading health advice. globally, there are no standards across various herbal products to authenticate their contents, safety or efficacy, and there is generally an absence of high-quality scientific research on product composition or effectiveness for anti-disease activity. presumed claims of therapeutic benefit from herbal products, without rigorous evidence of efficacy and safety, receive skeptical views by scientists. unethical practices by some herbalists and manufacturers, which may include false advertising about health benefits on product labels or literature, and contamination or use of fillers during product preparation, may erode consumer confidence about services and products. paraherbalism an example of a herbal medicine resource: the bark of the cinchona tree contains quinine, which today is a widely prescribed treatment for malaria. the unpurified bark is still used by some who can not afford to purchase more expensive antimalarial drugs. paraherbalism is the pseudoscientific use of extracts of plant or animal origin as supposed medicines or health-promoting agents. phytotherapy differs from plant-derived medicines in standard pharmacology because it does not isolate and standardize the compounds from a given plant believed to be biologically active. it relies on the false belief that preserving the complexity of substances from a given plant with less processing is safer and potentially more effective, for which there is no evidence either condition applies. phytochemical researcher varro eugene tyler described paraherbalism as "faulty or inferior herbalism based on pseudoscience", using scientific terminology but lacking scientific evidence for safety and efficacy. tyler listed ten fallacies that distinguished herbalism from paraherbalism, including claims that there is a conspiracy to suppress safe and effective herbs, herbs can not cause harm, that whole herbs are more effective than molecules isolated from the plants, herbs are superior to drugs, the doctrine of signatures (the belief that the shape of the plant indicates its function) is valid, dilution of substances increases their potency (a doctrine of the pseudoscience of homeopathy), astrological alignments are significant, animal testing is not appropriate to indicate human effects, anecdotal evidence is an effective means of proving a substance works and herbs were created by god to cure disease. tyler suggests that none of these beliefs have any basis in fact. traditional systems