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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 thoroughly tested for effectiveness or interactions with other herbs, supplements, drugs, or foods. Products added to herbal preparations may also cause interactions. It is important to tell your health care 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 as an anti-inflammatory agent. Few studies have evaluated its effectiveness for any condition. It is consumed 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. It may interfere with the way the body metabolizes some drugs, causing too high a level of the drug in some people. As with any medicinal herb, consult your health care 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 have evaluated echinacea's effectiveness to prevent or shorten the course of a cold, but none was conclusive. A study in the July 2005 New England Journal of Medicine, however, clearly showed that echinacea was ineffective in preventing or treating colds. Study results also have shown that long-term use can suppress 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.



Traditionally used to treat fevers, feverfew 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 rebound headaches. Feverfew should not be used with non-steroidal anti-inflammatory drugs, because those drugs may alter feverfew's effectiveness. It should not be used with warfarin and other anticoagulants.


(Cloves, root)

Garlic is used for lowering cholesterol and blood pressure and has antibacterial effects. Reports from small, short-term and poorly described studies indicate that it may cause non-significant or small reductions in total and LDL cholesterol. German research results on garlic's cholesterol-lowering effect, however, have been skewed for a positive effect, the FDA says. Researchers are currently exploring garlic's possible role in preventing cancer. Garlic is considered safe by the FDA. 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 the ginger can relieve pregnancy-induced chemotherapy-induced nausea. Other areas under investigation are in surgery and motion-induced nausea. Reported side effects include bloating. gas, heartburn, and nausea.



Ginkgo leaf extract has been used to treat a variety of conditions, including 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, which can cause seizures and, in large amounts, death. Because some data to suggest that ginkgo can increase the risk for bleeding, it should not be used with non-steroidal anti-inflammatory drugs, anticoagulants, anticonvulsant drugs, or tricyclic antidepressants.



Ginseng is used as a tonic and aphrodisiac, even as a cure-all. Research is inconclusive about its effectiveness, in part 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, non-steroidal 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 of toxicity—including skin, mouth, throat, and gastric irritation—and because of the plant's endangered species status.

Milk Thistle


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

Saint John's Wort

(Flower, leaf)

Saint John's wort is used as an antidepressant. A major study is underway to evaluate this herb's safety and effectiveness compared with other antidepressants. Recent studies have not confirmed that there is more than a minimal effect on depression. Further 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.

Saw Palmetto


Saw palmetto is used to treat benign prostatic hypertrophy (BPH). Studies have confirmed the effectiveness of the herb in treating this condition. Side effects are gastrointestinal upset and headache, both mild.



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