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A Guide to Common Medicinal Herbs

Here's a look at some of the more common medicinal herbs. Most herbs have not been completely tested for effectiveness or interactions with other herbs, supplements, drugs, or foods. Products added to herbal preparations may also cause interactions. Be aware that "natural" does not necessarily mean "safe." It is important to tell your healthcare providers about any herb or dietary supplement you are using.



Considered by some to be a cure-all, chamomile is commonly used in the United States as a sedative. It is used in Europe for wound healing and to reduce inflammation or swelling. Few studies have evaluated its effectiveness for any condition. Chamomile is used as a tea or applied as a compress. It is considered safe by the FDA. It may increase drowsiness caused by drugs or other herbs or supplements. Chamomile may interfere with the way the body uses some drugs, causing too high a level of the drug in some people. As with any medicinal herb, consult your healthcare provider prior to taking it.


(Leaf, stalk, root)

Echinacea is commonly used to treat or prevent colds, flu, and infections, and for wound healing. More than 25 published studies looked at how well echinacea worked to prevent or shorten the course of a cold, but none was conclusive. And a 2014 study compared echinacea with a placebo for treating colds. It found that echinacea did not have any effect on a cold. Study results also have shown that long-term use can curb the body's immune system. It should not be used with drugs that can cause liver problems. People allergic to plants in the daisy family, which includes ragweed, chrysanthemums, marigolds, and daisies, may be more likely to have an allergic reaction to echinacea.



Feverfew was traditionally used to treat fevers. It is now commonly used to prevent migraines and treat arthritis. Some research has shown that certain feverfew preparations can prevent migraines. Side effects include mouth ulcers and gastrointestinal irritation. People who suddenly stop taking feverfew for migraines may experience the return of their headaches. Feverfew should not be used with nonsteroidal anti-inflammatory drugs, because those drugs may change feverfew's effectiveness. It should not be used with warfarin and other drugs that make it hard for the blood to clot.


(Cloves, root)

Garlic is used for lowering cholesterol and blood pressure. It has antibacterial effects. Reports from small, short-term, and poorly described studies show that it may cause small reductions in total and LDL cholesterol. German research results on garlic's cholesterol-lowering effect, however, have been distorted for a positive effect, the FDA says. Researchers are currently exploring garlic's possible role in preventing cancer. The FDA considers garlic safe. It should not be used with warfarin, because large amounts of garlic may affect clotting. For the same reason, large amounts should not be taken before dental procedures or surgery.



Ginger is used to ease nausea and motion sickness. Research suggests that ginger can relieve nausea caused by pregnancy or chemotherapy. Other areas under investigation are in surgery and nausea caused by motion. Reported side effects include bloating, gas, heartburn, and nausea.



Ginkgo leaf extract has been used to treat a variety of conditions like asthma, bronchitis, fatigue, and tinnitus. It is also used to improve memory and to prevent dementia and other brain disorders. Some studies have supported its slight effectiveness, although exactly how gingko works isn't understood. Only extract from leaves should be used. Seeds contain ginkgo toxin. This toxin can cause seizures and, in large amounts, death. Because some information suggests that ginkgo can increase the risk for bleeding, it should not be used with nonsteroidal anti-inflammatory drugs, anticoagulants, anticonvulsant drugs, or tricyclic antidepressants.



Ginseng is used as a tonic and aphrodisiac, even as a cure-all. Research is uncertain about its effectiveness, partly because of the difficulty in defining "vitality" and "quality of life." There is a large variation in the quality of ginseng sold. Side effects are high blood pressure and tachycardia. It's considered safe by the FDA, but shouldn't be used with warfarin, heparin, nonsteroidal anti-inflammatory drugs, estrogens, corticosteroids, or digoxin. People with diabetes should not use ginseng.


(Root, rhizome)

Goldenseal is used to treat diarrhea, and eye and skin irritations, and as an antiseptic. It is also an unproven treatment for colds. Goldenseal was found to have berberine. Berberine is a plant alkaloid with a long history of medicinal use in both Ayurvedic and Chinese medicine. Studies have shown that goldenseal is effective for diarrhea, but it's not recommended because it is considered poisonous. It can cause skin, mouth, throat, and gastric irritation. It is also not recommended because of the plant's endangered species status.

Milk Thistle


Milk thistle is used to treat liver conditions, high cholesterol, and to reduce the growth of cancer cells. Milk thistle is a plant that originated in the Mediterranean region. It has been used for many different illnesses over the last several thousand years, especially liver problems. Although study results are uncertain, some promising information exists.

Saint John's Wort

(Flower, leaf)

Saint John's wort is used as an antidepressant. Recent studies have not confirmed that there is more than a slight effect on depression. More research is needed to determine the best dose. A side effect is sensitivity to light, but this is only noted in people taking large doses of the herb. St. John's work can cause a dangerous interaction with other commonly used medicines. Always talk with your healthcare provider before using this herb.

Saw Palmetto


Saw palmetto is used to treat benign prostatic hypertrophy (BPH). Recent studies have not found it to be effective for this condition, however. Side effects are gastrointestinal upset and headache, both mild.



Valerian is used to treat sleeplessness and to reduce anxiety. Research suggests that valerian may be a helpful sleep aid, but there are no well-designed studies to confirm the results. In the United States, valerian is used as a flavoring for root beer and other foods. As with any medicinal herb, talk with your healthcare provider prior to taking it.

Online Medical Reviewer: Turley, Ray, BSN, MSN
Date Last Reviewed: 1/8/2016
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