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Herbal therapy involves the use of plants or plant parts for medicinal purposes. Although many herbs have been used by various societies for hundreds of years, there is insufficient scientific evidence regarding their safety and effectiveness.

Herbs may be available as fresh, dried or liquid products. Many are available as supplements (e.g., capsule, tablet, powders). Herbs are commonly consumed as an herbal infusion (when an herb is allowed to steep in hot water, similar to tea).

There are a wide variety of herbs used for their purported effects on the body. Some common herbs include chamomile, echinacea, ginkgo biloba, ginseng, goldenseal, peppermint, St. John’s wort and valerian. Potential effects include mild sedation, increased energy and mental alertness, and immune-system stimulation.

Herbs can also produce adverse side effects that range from bothersome (e.g., nausea, abdominal discomfort) to potentially deadly (e.g., hypertension, serious liver damage). Herbs may also interfere with a wide variety of medications, medical conditions, supplements, other herbs, and foods and beverages. For example, many herbs may affect liver functioning, some may increase the risk of bleeding (especially in patients on anticoagulant medications) and others may dangerously intensify effects of certain medications (e.g., sedatives).

Consumers are advised to consult with their physician before taking any type of herb. In general, herbal therapy is not recommended for children, the elderly, and women who are pregnant or breastfeeding. The safety of many herbs for use in these circumstances has not been clearly established.

Herbs are regulated by the U.S. Food and Drug Administration (FDA) as a food, not as a drug. Thus, they do not undergo the rigorous testing and approval process that are required of medications. Manufacturers are responsible for assuring (but are not required to prove) the safety and effectiveness of their products. In addition, the quality and purity of some herbal products has been called into question.