Echinacea has antiviral, antifungal, anti-inflammatory, and antibacterial properties. Although taken internally, it can also be used topically on wounds or inflamed skin. It has been used to treat candida, a maddening yeast infection, and in some cases used as a mouthwash to treat gingivitis.

There are several medicinal species of echinacea. All are native to the Great Plains and southern United States, but they are becoming scarce in the wild today due to overharvesting by paid gatherers. Some medicinal supplies come from cultivated fields in the United States and Europe.

One species, Echinacea purpurea, is a herbaceous plant three to four feet in height with reddish, purple, or pinkish flowers. It is commonly called purple coneflower, black Sampson, or Kansas snakeroot. The leaves, roots, and flowers are the medicinal parts of this plant.

North American Indians were the first to use another species, E. angustifolia, as a medicine to treat snakebite, toothache, sore throats, respiratory ailments, and skin wounds. In the 1700s, European settlers applied it to saddle sores on their horses.

It wasn’t until a century later on the Great Plains that echinacea became better known as medicine. In Nebraska, Dr. H. C. F. Meyer created Meyer’s Blood Purifier, a concoction of echinacea root extract, hops, and wormwood. Dr. Meyer touted his patent medicine as being "valuable for the bites of serpents and insect stings," and it became quite popular. Within a few decades, echinacea became the most widely used medicinal plant in the country. It got an unlooked-for marketing boost when Louis Pasteur discovered that many diseases and conditions were caused by germs. Then its advocates could say that echinacea was a germ killer.

In that era, echinacea was thought by physicians to be a treatment for many infectious diseases. By the 1930s, however, it fell out of favor, partly because some of its supporters linked it with the outdated idea that germs were generated spontaneously within the blood.

While Americans’ interest waned, however, Europeans’ continued. Researchers from one German company started to import echinacea seeds from North America. Eventually, they discovered that they were growing and testing E. purpurea rather than E. angustifolia, which was the most widely used species. As a result, nearly all of the scientific research conducted with echinacea in the last 50 years has been on that species. Most of those studies use a formulated ethanol extract—that is, an extract mixed with alcohol. The medicinal extract is made from the aerial parts (leaves and flowers) of the plant.

In Germany in 1994, there were more than 300 echinacea preparations on the market, and doctors wrote 2.5 million prescriptions for this herb alone.

"It’s funny how, in the early part of this century, echinacea was widely used by Americans. It was in most people’s medicine cabinets, and then it fell out of fashion," says Dr. Dentali. "Now, it’s back, partly because it’s been proven safe and effective in Germany."

Although dozens of studies prove echinacea’s effectiveness as an immune stimulator, scientists still aren’t certain which active ingredients are responsible. Some evidence, however, points to a group of polysaccharides, a combination of different kinds of sugar molecules. By conducting lab tests and injecting the plant sugars directly into humans, researchers have found that polysaccharides increase phagocytosis.

In addition, echinacea contains many other compounds that seem to have antiviral properties and a gearing-up effect on the immune system. "With herbs, it not always possible to isolate all of the active ingredients," says Dr. Dentali. But the research on echinacea is leading to a better understanding of how it works, he points out.

As for which species of echinacea is the more powerful medicine for your immune system, that isn’t known yet. Suffice it to say that the major medicinal species of echinacea appear to have similar benefits. Perhaps the species of the future will be a hybrid.

In health food stores, you’ll probably find dozens of echinacea products. The herb comes as a tincture, a freeze-dried extract in capsules or tablets, and a simple herb powder packaged in capsules.

Look at the labels carefully, says Jennifer Brett, N.D., a naturopathic doctor at the Wilton Naturopathic Center in Stratford, Connecticut. There have been problems with adulteration—that is, replacing echinacea with less potent herbs. The ground-up roots of Missouri snakeroot are sometimes passed off as echinacea.

Your best bet is to look for a label that says explicitly that the product contains the leaves and flowers of E. purpurea or the roots of E. angustifolia. Sometimes, you’ll find products containing both varieties as well as E. pallida. If you do, that’s fine.

"Echinacea tincture also has a distinctive buzz to it. The more root in the mixture, the stronger the sting," says Dr. Dentali. "It ought to make your tongue tingle and numb your mouth."

The revved-up effect, however, is short-lived. Research suggests that echinacea loses its effectiveness with continuous use. Consequently, you will want to use it only when you feel a cold coming on or when your immune system is weakened by stress, says Dr. Brett.

"It’s not a good idea to take this on a daily basis. If everyone in your office is sick, however, and you have no doubt that you’re going to get sick, you can take it as a prophylactic," she says. "Just remember that it’s most potent in those first few days that you take it."

If you have an autoimmune disease such as lupus or rheumatoid arthritis, you should be cautious, says Dr. Lee. "These diseases are partly due to an already overactive immune system. Anything that stimulates the immune system may, in theory, be harmful," she says. "You may be able to use echinacea really short-term, but I’d consider other choices, such as zinc."

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