The decorative plant Echinacea purpurea, or purple coneflower, has been one of the most popular herbal medications in both the United States and Europe for over a century.

Native Americans used the related species Echinacea angustifolia for a wide variety of problems, including respiratory infections and snakebite. Herbal physicians among the European colonists quickly added the herb to their repertoire. Echinacea became tremendously popular toward the end of the nineteenth century, when a businessman named H.C.F. Meyer promoted an herbal concoction containing E. angustifolia. The garish, exaggerated, and poorly written nature of his labeling helped define the characteristics of a "snake oil" remedy.

However, serious manufacturers developed an interest in echinacea as well. By 1920, the respected Lloyd Brothers Pharmaceutical Company of Cincinnati, Ohio, counted echinacea as its largest-selling product. In Europe, physicians took up the American interest in E. angustifolia with enthusiasm. Demand soon outstripped the supply coming from America, and, in an attempt to rapidly plant echinacea locally, the German firm Madeus and Company mistakenly purchased a quantity of Echinacea purpurea seeds. This historical accident is the reason why most echinacea today belongs to the purpurea species instead of angustifolia. Another family member, Echinacea pallida, is also used.

Echinacea was the number one cold and flu remedy in the United States until it was displaced by sulfa antibiotics. Ironically, antibiotics are not effective for colds, while echinacea appears to offer some real help. Echinacea remains the primary remedy for minor respiratory infections in Germany, where over 1.3 million prescriptions are issued each year.

In Europe, and increasingly in the US as well, echinacea products are widely used to treat colds and flus.

The best scientific evidence about echinacea concerns its ability to help you recover from colds and minor flus more quickly. The old saying goes that "a cold lasts 7 days, but if you treat it, it will be over in a week." However, good, if not entirely consistent, evidence tells us that echinacea can actually help you get over colds much faster.9-19,40 It also appears to significantly reduce symptoms while you are sick. Echinacea may also be able to "abort" a cold, if taken at the first sign of symptoms. However, taking echinacea regularly throughout cold season is probably not a great idea. Evidence suggests that it does nothelp prevent colds.20,21,23,24

Until recently, it was believed that echinacea acted by stimulating the immune system. Test tubeand animal studies had found that various constituents of echinacea can increase antibody production, raise white blood cell counts, and stimulate the activity of key white blood cells.1-6However, most recent studies have tended to cast doubt on this theory.7,37,41,42,56-57 The fact that regular use of echinacea does not appear to help prevent colds (or genital herpes 8) also somewhat argues against an immune-strengthening effect. Thus, at present, it can only be said that we don’t understand the means by which echinacea affects cold symptoms.

Echinacea has been proposed for the treatment and/or prevention of other acute infections as well. One small double-blind study found that use of an herbal combination containing echinacea enhanced the effectiveness of antibiotic treatment for acute flare-ups of chronic bronchitis.43 However, two other studies failed to find benefit for ear infectionsin children.44,64

Finally, echinacea is frequently proposed for general immune support. However, as discussed above there is some reason to think that it is not effective for this purpose.