Herbal Medicine

Early written records

Historical surveys of pharmacy trace the written use of medicinal plants to some of the earliest surviving documents. A review by the pharmacognosist Biljana Bauer Petrovska describes a Sumerian clay tablet from about 5,000 years ago with 12 drug recipes referring to more than 250 plants, and the Egyptian Ebers Papyrus of about 1550 BCE with around 800 prescriptions. These records show that plants were written down as remedies; they do not show that the remedies had the effects attributed to them.

Greek, Roman and medieval materia medica

The same review describes a Greek and Roman literature that catalogued medicinal plants. It credits Hippocratic writings with about 300 plants, Theophrastus (371 to 287 BCE) with a classification of more than 500, and the De Materia Medica of Dioscorides (about 77 CE) with 944 drugs, 657 of them of plant origin. Galen, in the second century CE, listed drugs with similar actions that could be substituted for one another. In medieval Europe, the review notes, monk-physicians relied on a small set of medicinal plants grown within monasteries.

From plant drugs to isolated compounds

From the early nineteenth century, chemists began isolating alkaloids from plants, starting with the opium poppy in 1806, a development the review treats as the beginning of scientific pharmacy. Many later drugs derive from plant compounds, but herbal medicine on this page means the use of whole plants or plant extracts rather than single purified drugs. The review also describes a German approach called rational phytotherapy, based on preparations whose action depends on dose and on identified active constituents.

Botanical movements in North America and Britain

In the United States, a popular botanical movement formed around the lay healer Samuel Thomson (1769 to 1843) in the early nineteenth century. The medical librarian and historian Michael Flannery describes Thomsonianism as a grassroots health crusade that favored practical reliance on plant remedies over formal medical schooling, while depending on a literate public to spread its system through books and pamphlets.

In the United Kingdom, the National Institute of Medical Herbalists, a professional body of herbal practitioners, dates its origins to 1864 and states that it has operated a register of medical herbalists for more than 100 years. This is the organization's own account of its history.

Herbal medicine, herbalism and phytotherapy

Herbal medicine, herbalism, botanical medicine and phytotherapy are often used interchangeably for the therapeutic use of plants. Phytotherapy is sometimes used more narrowly for a pharmacologically framed approach built on dosed, characterized extracts, as in the German rational phytotherapy described by Petrovska. Western herbal medicine is a label used, for example in Australian research, for practitioners working from a European and North American materia medica rather than an Asian medical system.

Extracts, products and plant names

Clinical research usually tests a specific preparation, such as the hypericum extracts in the Cochrane review of St John's wort, rather than a plant in general. The Cochrane review of echinacea notes that products sold under one plant name differ appreciably in composition because of different plant material, extraction methods and added components. The name of an herb alone therefore does not identify what a product contains, and results for one extract may not apply to another.

Relation to traditional medical systems

Herbal prescribing is also part of other medical systems, including Ayurveda, Chinese herbal medicine, Japanese Kampō and Unani medicine, each with its own theory and texts and each covered on its own page. Shared plants or similar names do not make these practices equivalent. Safety findings also differ by source: one overview of systematic reviews found that adulteration and contamination were reported most often for traditional Indian and Chinese remedies, a finding that should not be transferred automatically to other products.

Self-care and retail products

Much herbal use takes place without a practitioner, through teas, capsules, tablets and liquid extracts bought from shops, pharmacies or online sellers. A 2019 analysis of DNA testing covered herbal products sold as medicines or foods in 37 countries, which indicates how widely such products are traded. Because composition varies between products, two people using the same herb by name may be taking quite different preparations.

Prescribing by Western herbal practitioners

A national survey of members of the National Herbalist Association of Australia, published in 2006, described how professional Western herbalists prescribe. Most built individualized formulas of several herbs after a consultation, rather than giving single herbs, and most dispensed them from their own clinic dispensary. Concentrated liquid extracts in ratios of 1:1 or 1:2, plant material to liquid, were the most common form, with teas, powders and manufacturer-made tablets or capsules also in use.

The same survey reported topical creams, poultices, washes, gargles, eyebaths, pessaries and douches alongside internal prescriptions. Dosage ranges varied between practitioners, though most described using doses intended to be pharmacologically active. The authors noted that professional prescribing differs from commercial use, which relies more on single herbs or pre-formulated tablets. Practice in other countries may differ, and the survey does not describe the content of a typical consultation.

Training and professional bodies

Training routes for herbal practitioners vary by country, and this draft verified the standards of one professional body. The National Institute of Medical Herbalists in the United Kingdom states that its members need degree-level qualifications or equivalent, that it accredits training establishments and sets the profession's educational standards, and that members follow its codes of conduct, ethics and practice, with complaints and disciplinary procedures. These requirements apply to its members, not to everyone who sells herbs or uses the title herbalist.

Uses that have been studied

People use herbal products for many purposes, and clinical research has examined some of them. Systematic reviews cited on this page concern St John's wort extracts for major depression, herbal preparations such as devil's claw, white willow bark and cayenne for nonspecific low back pain, and echinacea for preventing or treating the common cold. These are specific products studied for specific outcomes, and findings for one cannot be carried over to other herbs or other uses.

Traditional and practitioner claims

Historical materia medica, from the Hippocratic writings and Dioscorides onward, attributed particular actions to hundreds of plants. Western herbal practitioners today often frame treatment around an individualized formula for the person rather than one herb for one diagnosis. These traditional and practitioner indications record how plants have been used and understood; they are not in themselves evidence that the described effects occur.

Use during pregnancy

Herbal products are also used in pregnancy. In a multinational survey of women in Europe, North America and Australia conducted in 2011 and 2012, 29.3 percent reported using an herbal medicine while pregnant. The authors classified 27 of the 126 herbs they could identify as contraindicated in pregnancy, and these were used by 20 percent of the women who named a specific herb. Safety concerns are discussed under Safety and Suitability.

St John's wort and major depression

A Cochrane review updated in 2008 included 29 randomized double-blind trials with 5,489 people with major depression. Hypericum extracts produced higher response rates than placebo, with a response rate ratio of 1.28 in nine larger trials and 1.87 in nine smaller ones, and response rates similar to tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs). Fewer people stopped hypericum because of adverse effects. The authors cautioned that trials from German-speaking countries reported more favorable results, which complicates interpretation.

The United States National Center for Complementary and Integrative Health (NCCIH) summarizes St John's wort as possibly helpful for mild or moderate depression and states that its effect in severe depression, and over periods longer than 12 weeks, is uncertain.

Herbal preparations for low back pain

A Cochrane review of 14 randomized trials with 2,050 adults with nonspecific low back pain, with searches to 2014, found that cayenne (Capsicum frutescens) reduced pain more than placebo. Devil's claw, white willow bark, comfrey, Brazilian arnica and lavender essential oil also appeared to reduce pain more than placebo, but evidence for these was of moderate quality at best. Reporting in the trials was generally poor, no significant adverse events were noted, and the authors called for larger trials against standard treatments.

Echinacea and the common cold

A Cochrane review of 24 double-blind trials with 4,631 participants compared echinacea preparations with placebo. None of 12 prevention comparisons found a statistically significant difference in the number of people with at least one cold, although a post hoc pooling suggested a relative reduction of 10 to 20 percent, and only one of seven treatment trials showed shorter colds. The authors concluded that benefit for treating colds had not been shown and that any preventive effect was of questionable clinical relevance.

Individualized prescribing

The individualized formulas typical of practitioner herbalism have been studied far less than single extracts. A 2007 systematic review found three randomized trials. In knee osteoarthritis, apparent benefits probably reflected baseline differences; in irritable bowel syndrome, individualized treatment did better than placebo on four of five outcomes but worse than a standardized herbal formula; and for preventing chemotherapy toxicity it was no better than placebo. The reviewers found no convincing evidence for individualized herbal medicine in any indication.

Herb-drug interactions

Herbs can change how medicines act. A 2009 systematic review identified 128 case reports or series and 80 clinical trials on interactions involving seven popular herbs. Trials showed that St John's wort, by inducing cytochrome P450 enzymes and the P-glycoprotein transporter, lowers blood levels or speeds clearance of drugs including ciclosporin, tacrolimus, digoxin, warfarin, oral contraceptives, indinavir and irinotecan. Interactions were also reported for ginkgo, ginseng, garlic and kava, although the significance of many was uncertain.

NCCIH states that interactions with St John's wort can weaken the effects of life-saving medicines, and that combining it with drugs that raise serotonin may increase serotonin-related side effects, which can be serious. Its listed examples include transplant, HIV, cancer, anticoagulant, heart and contraceptive medicines.

Liver injury and other adverse events

In the United States Drug-Induced Liver Injury Network, 130 of 839 people enrolled at referral centers between 2004 and 2013 (15.5 percent) had liver injury attributed to herbal and dietary supplements, and this share rose from 7 to 20 percent over the study period. Injury from supplements other than bodybuilding products was mostly hepatocellular, occurred mainly in middle-aged women, and led to death or liver transplantation more often than injury from conventional medicines (13 versus 3 percent). These referral cases do not give a population rate. NCCIH lists photosensitivity, diarrhea, dizziness and sleep disturbance among side effects of St John's wort.

Adulteration, contamination and quality

An overview of 26 systematic reviews found herbal medicinal products adulterated or contaminated with substances including microbes, fungi, pesticides, toxic heavy metals and undeclared prescription drugs. Reported consequences included arsenic, lead or mercury poisoning, liver and kidney failure, and death. In a 2019 analysis of DNA testing of 5,957 commercial herbal products from 37 countries, 27 percent did not match their labeled species, containing substitutes, fillers or none of the declared plant, with proportions differing widely between regions.

Even correctly identified products vary, because species, plant parts and extraction methods differ, as the Cochrane review of echinacea notes. Quality differences of this kind make it difficult to apply trial results to a product on the shelf.

Pregnancy and care boundaries

Human safety data for herbs in pregnancy are scarce. In the multinational survey, women who took an herb classified as contraindicated in pregnancy were three times more likely to have had it recommended by a healthcare practitioner than by an informal source, and the authors called for more education among practitioners. NCCIH states that St John's wort use in pregnancy may increase the risk of birth defects. Herbal products should not delay or replace assessment and necessary medical care.