Echinacea is the name of a genus of native North American plants with reddish or purplish flowers.
There are nine species, but only three of them (E. angustifolia, E. pallida, E. purpurea) are used as botanical medicines. Gardeners may recognize echinacea as the purple coneflower.
Echinacea was used traditionally by many Native American tribes to treat snakebite and many other ailments, and settlers learned of its properties from the Indians.
Most of the research on the chemistry and pharmacology of these plants has been conducted in Europe, where until fairly recently echinacea was a much more popular herb than in the United States.
The current enthusiasm for echinacea derives from research suggesting that it can stimulate the immune system and help fight off viral infections such as colds or influenza.
In this country, echinacea is available primarily as a tincture (alcohol-based extract) or as capsules of dried leaves and stems collected when the plant is in flower.
Capsules of dried root are also marketed. Fresh-squeezed juice, widely used in Germany, is rarely sold here.
**Active Ingredients**
The three species are not interchangeable, although they may sometimes be confused with one another. Each may have a different balance of active compounds. Of course, the roots also differ from the aboveground parts of the plant, though both are utilized medicinally.
The chemistry of echinacea is complex, and no single ingredient has been identified as primarily responsible for the therapeutic activity.
A caffeic acid glycoside, echinacoside, makes up approximately 0.1 percent of the leaves and stems, which also contain cichoric acid. Fresh echinacea or its juice contains a volatile substance not found in the dried plant material.
The roots of E. angustifolia contain chemicals called alkamides.
**Uses**
Echinacea has become extremely popular for the treatment of colds, influenza, and other respiratory tract infections.
Although the herb does not seem to kill viruses directly, it is believed to stimulate or modulate the immune system, allowing the host to fight off infection. In one European study, people taking echinacea recovered from their colds four days earlier than those taking a placebo.
Both the root of E. pallida and the aboveground parts of E. purpurea are used in Europe for this purpose. It is usually given just at the first appearance of symptoms, rather than taken daily as a preventive.
One study of three hundred people (in three groups, taking E. purpurea, E. angustifolia, or placebo) over twelve weeks was not able to demonstrate a significant advantage of the botanical medicines over placebo. The authors hypothesize that echinacea might reduce the rate of infection by 10 to 20 percent, undetectable at that sample size.
The herb is given orally or by injection in Germany for other infections as well, including prostatitis and urinary tract infections.
Test tube and animal research has shown that echinacea extracts have significant anti-inflammatory activity.
When applied to the skin, the extract is almost as effective as a potent anti-inflammatory drug, indomethacin, used topically. Topically, the extracts have been used to help hasten the healing of stubborn wounds, eczema, psoriasis, and herpes simplex.
Intriguing research in rats demonstrates an ability of E. purpurea extract to help protect the animals from side effects of radiation. In this study, the animals used up vitamin E in particular more quickly than the rats not receiving echinacea.
To maximize the benefit of the herb, it should be given together with a multiple vitamin. (In Australia, a formulation that includes echinacea, vitamin A, vitamin C, vitamin E, zinc, and garlic is prescribed at the first sign of viral respiratory infection.)
So far as we know, the extract has not been studied in humans undergoing radiation.
Preliminary studies suggest that it may be of some use in treating certain cancers. Much more research is needed on this potential application.
**Dose**
When fresh-squeezed juice is used, the dose is 6 to 9 ml, or approximately 1½ teaspoons (= 7.5 ml). Other oral formulations should supply the equivalent of 900 mg of the herb daily.
One study indicated that short-term use could boost cell-mediated immunity, but that repeated use over a period of weeks reduced the immune response. This interpretation of the results has been questioned, but most authorities suggest six to eight weeks as the maximum time to take echinacea preparations.
One study using the fresh juice of E. purpurea showed no problems for people taking it for up to twelve weeks. The herb should be stored away from light to maintain potency.
A standardized German product is available in the United States under the brand name EchinaGuard.
**Special Precautions**
One of the problems with echinacea is that the different species may be confused by people gathering the herb from the wild.
Some commercial products have even been contaminated with plants of a quite different species, Parthenium integrefolium.
As with most herbal products, the possibility of microbial contamination can’t be ruled out, so if the medicine is intended for a person with a compromised immune system, it should be administered in a tea made with boiling water.
Many authorities warn against using echinacea for people with autoimmune diseases, multiple sclerosis, or other serious conditions such as tuberculosis, AIDS, or leukemia. These precautions appear to rest on theoretical grounds, and are not universally accepted, but we believe it is prudent to respect them.
Echinacea species belong to the family of asters. Anyone allergic to ragweed or other flowers in the family should probably avoid echinacea products.
One woman in Australia had to rush to the emergency room for treatment of anaphylaxis after taking a commercial echinacea extract. Specific testing confirmed that she had become sensitive to the herb.
**Adverse Effects**
Side effects have rarely been reported with the use of echinacea.
In a recent study of echinacea extracts for the prevention of colds, 18 percent of the patients taking E. angustifolia, 10 percent of those taking E. purpurea, and 11 percent of those on placebo experienced side effects.
The researchers did not specify what reactions occurred but reported that they were not serious and did not require treatment. Echinacea has an unpleasant aftertaste.
**Possible Interactions**
Interactions of echinacea with other medications are based on theoretical concerns.
Some of the alkaloids found in echinacea are similar to plant chemicals that can be damaging to the liver. Thus, some doctors suggest that echinacea should not be used with other drugs that can have negative effects on the liver, such as Nizoral, methotrexate, Cordarone, or anabolic steroids.
One reference notes that flavonoids found in E. purpurea affect the enzyme (CYP 3A4) responsible for metabolizing many common drugs.
This is the same enzyme affected by grapefruit, but we do not know if the effect would be clinically important. If it were, medications as varied as cyclosporine, Plendil, Procardia, Sular, Propulsid, Hismanal, Mevacor, Zocor, Tegretol, or Viagra could reach higher levels in the body. Coumadin might also be affected. Monitoring drug response is important.

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