herbal medicine, use of natural plant substances (botanicals) to treat and prevent illness. The practice has existed since prehistoric times and flourishes today as the primary form of medicine for perhaps as much as 80% of the world's population. Over 80,000 species of plants are in use throughout the world. Along with acupuncture, herbal medicine is considered primary health care in China, where it has been in documented use for over 2,500 years.

Herbs may be used directly as teas or extracts, or they may be used in the production of drugs. Approximately 25% of the prescription drugs sold in the United States are plant based. Many more herbal ingredients are present in over-the-counter drugs, such as laxatives. Medicines that come from plants include aspirin from willow bark (Salix species) and digitalis from foxglove (Digitalis purpurea).

Scientific interest in herbal medicine in the United States has lagged behind that in the countries of Asia and W Europe; in Germany, for example, one third of graduating physicians have studied herbal medicine, and a comprehensive therapeutic guide to herbal medicines has long been published there. Nonetheless, millions of people in the United States use herbal products to treat a wide variety of ailments or to enhance health. Among the more popular remedies used are ginseng, to increase stamina and as a mild sedative; St.-John's-wort, for mild depression; echinacea, to aid the immune system and alleviate colds; kava, to calm anxiety and treat insomnia; saw palmetto, for enlarged prostate; and ginkgo biloba, to improve short-term memory (see ginkgo). Some people have used botanicals in an attempt to stave off serious illnesses such as AIDS.

This widespread use has prompted demands that herbal remedies be regulated as drugs to insure quality standards. The U.S. Food and Drug Administration (FDA) can require a clinical trial on any herb that has a health claim on its label, but medical testing, which is geared toward observing a particular active component, is difficult to apply to herbs, which may have many interacting ingredients. Debate over botanicals' validity and safety as medicines and over the appropriate degree of government regulation continues. The Dietary Supplement Health and Education Act, passed in 1994, reclassified herbs as dietary supplements rather than food additives. It forbids unreasonable health claims by the manufacturers, but makes it the FDA's responsibility to prove that a marketed product is unsafe. (In contrast, in prescription and over-the-counter drugs, it is the manufacturer's responsibility to prove safety and effectiveness before a drug can be marketed.)

Another concern surrounding herbal medicine is the availability of wild plants for a growing market; it is feared that the limited supplies of known wild herbs are being threatened by overharvesting and habitat loss. The potential of isolating beneficial drugs from plants, however, has prompted large pharmaceutical companies to contribute to the conservation of the tropical rain forest. Biologists have called for more careful study of medicinal plants, especially regarding their capacity for sustainable harvesting and the effects of cultivation on their efficacy as medicaments.

herbal, early botanical book containing descriptions and illustrations of herbs and plants with their properties, chiefly those qualities that made them useful as medicines or condiments. Most of the herbals were written between c.1470 and c.1670; they were especially popular in England and Germany. Among the famous herbalists were Gaspard Bauhin, Otto Brunfels, Hieronymus Bock, and Leonhard Fuchs, all active during the 16th cent. Mingled with illustrations of often painstaking accuracy were fantastic figures and many superstitious descriptions of the magical powers of plants, e.g., the doctrine of signatures. This theory of herbal medicine was based on the superficial resemblance of certain plants or plant parts to specific human organs or parts. The appropriate herb was used for any disorder of its human counterpart. Thus certain heart-shaped leaves were thought to relieve heart disease; the convoluted walnut, brain disease; and the figworts, whose flowers have deep throats, were given for scrofula (hence the figwort family name Scrophulariaceae). The herbal began to disappear as medicine acquired a more scientific approach, but it has enjoyed a revival of interest as more people have turned to self-care and herbal medicine.

Ancient manual of plants used for medicinal purposes. Hundreds or thousands of medicinal plants were known in ancient India, China, and Greece and medieval Europe. In the late 16th century, European herbals began to include plants from the Western Hemisphere. Their accuracy varies widely, but many of the plants in herbals later became sources for drugs (e.g., digitalis).

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