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.

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What Is Echinacea Used for Today?  

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 not help prevent colds. 20,21,23,24

Until recently, it was believed that echinacea acted by stimulating the immune system. Test tube and 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. 1-6 However, 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 infections in 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.

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What Is the Scientific Evidence for Echinacea?  

Reducing the Symptoms and Duration of Colds  

Double-blind, placebo-controlled studies enrolling a total of more than 1,000 individuals have found that various forms and species of echinacea can reduce cold symptoms and help you get over a cold faster. 9-16,45, 56 The best evidence regards products that include the above-ground portion of E. purpurea . 58

For example, in one double-blind, placebo-controlled trial, 80 individuals with early cold symptoms were given either an above-ground E. purpurea extract or placebo. 17 The results showed that the people who were given echinacea recovered significantly more quickly: just 6 days in the echinacea group versus 9 days in the placebo group. And, symptom reduction with a whole plant formulation of E. purpurea was seen in a double-blind, placebo-controlled study of 282 people. 45

But, another study found that while above-ground E. purpurea can reduce the severity of cold symptoms, the root portion may not be effective. In this double-blind trial, 246 individuals with recent onset of a respiratory infection were given either placebo or one of three E. purpurea preparations: two formulations of a product made of 95% above-ground herb (leaves, stems, and flowers) and 5% root, and one made only from the roots of the plant. 18 The results showed significant improvements in symptoms with the above-ground preparations, but the root preparation was not effective. And, in a large, randomized study, researchers found that dried echinacea root (10.2 grams for the first 24 hours of a cold and 5.1 grams for the next 4 days) did not improve symptoms more than placebo or no treatment. 65

Not all research involving above-ground E. purpurea , however, has supported its beneficial effects. A double-blind, placebo-controlled study of the above-ground herb, enrolling 120 people, failed to find benefits compared to placebo treatment. 46 And an even larger trial (407 participants) failed to find a widely used above-ground extract helpful for treating children with respiratory infections. 47

Researchers have also investigated other species of echinacea with mixed results. Benefits were seen with a preparation of E. pallida root 38 and with an herbal beverage tea containing above-ground portions of E. purpurea and E. angustifolia (as well as some E. purpurea root extract). 39 On the other hand, a double-blind, placebo-controlled study failed to find benefit with a dry herb product consisting largely of E. purpurea root and E. angustifolia root. 40 And, another study failed to find benefit with E. angustifolia root extract. 59

The bottom line: at present, the best supporting evidence for echinacea involves the above-ground portion or whole plant extract of E. purpurea , but even here the results are inconsistent.

"Aborting" a Cold  

A double-blind study suggests that echinacea cannot only make colds shorter and less severe, it might also be able to stop a cold that is just starting. 19 In this study, 120 people were given E. purpurea or a placebo as soon as they started showing signs of getting a cold.

Participants took either echinacea or placebo at a dosage of 20 drops every 2 hours for 1 day, then 20 drops 3 times a day for a total of up to 10 days of treatment. The results were promising. Fewer people in the echinacea group felt that their initial symptoms actually developed into "real" colds (40% of those taking echinacea versus 60% taking the placebo actually became ill). Also, among those who did come down with "real" colds, improvement in the symptoms started sooner in the echinacea group (4 days instead of 8 days). Both of these results were statistically significant. 

Preventing Colds  

Several studies have attempted to discover whether the daily use of echinacea can prevent colds from even starting, but the results have not been promising.

In one double-blind, placebo-controlled trial, 302 healthy volunteers were given an alcohol tincture containing either E. purpurea root, E. angustifolia root, or placebo for 12 weeks. 20 The results showed that E. purpurea was associated with perhaps a 20% decrease in the number of people who got sick, and E. angustifolia with a 10% decrease. However, the difference was not statistically significant. This means that the benefit, if any, was so small that it could have been due to chance alone.

Another double-blind, placebo-controlled study enrolled 109 individuals with a history of four or more colds during the previous year, and gave them either E. purpurea juice or placebo for a period of 8 weeks. 21 No benefits were seen in the frequency, duration, or severity of colds. (Note: This paper is actually a more detailed look at a 1992 study widely misreported as providing evidence of benefit. 22 )

Similar results were seen in four other studies as well, enrolling a total of more than 350 individuals. 23,24,48,62

A study often cited as evidence that echinacea can prevent colds actually found no benefit in the 609 participants taken as a whole. 25 Only by looking at subgroups of participants (a statistically questionable procedure) could researchers find any evidence of benefit, and it was still slight.

However, a recent study using a combination product containing echinacea, propolis , and vitamin C did find preventive benefits. 49 In this double-blind, placebo-controlled study, 430 children age 1 to 5 years were given either the combination or placebo for 3 months during the winter. The results showed a statistically significant reduction in frequency of respiratory infections. It is not clear which components of this mixture were responsible for the apparent benefits seen.

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Dosage  

Echinacea is usually taken at the first sign of a cold and continued for 7 to 14 days. Longer-term use of echinacea is not recommended. The best (though not entirely consistent) evidence supports the use of products made from the above-ground portions of E. purpurea (specifically, flowers, leaves and stems); E. pallida root has also shown promise, but E. purpurea root appears to be ineffective.

The typical dosage of echinacea powdered extract is 300 mg 3 times a day. Alcohol tincture (1:5) is usually taken at a dosage of 3 to 4 ml 3 times daily, echinacea juice at a dosage of 2 to 3 ml 3 times daily, and whole dried root at 1 to 2 g 3 times daily. There is no broad agreement on what ingredients should be standardized in echinacea tinctures and solid extracts.

Note : A survey of available echinacea products found many problems. 50 In this 2003 analysis, about 10% had no echinacea at all; about half were mislabeled as to the species of echinacea present; more than half the standardized preparations did not contain the labeled amount of standardized constituents; and the total milligrams of echinacea stated on the label generally had little to do with the actual milligrams of herb present. A subsequent analysis performed in 2004 by the respected testing organization, ConsumerLab.com, also found many problems. 60

Many herbalists feel that liquid forms of echinacea are more effective than tablets or capsules, because they feel that part of echinacea's benefit is due to activation of the tonsils through direct contact. 26 However, there is no real evidence to support this contention.

Finally, goldenseal is frequently combined with echinacea in cold preparations. However, there is not a shred of evidence that oral goldenseal stimulates immunity, nor did traditional herbalists use it for this purpose. 27

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Safety Issues  

Echinacea appears to be generally safe. Even when taken in very high doses, it has not been found to cause any toxic effects. 29,51,52,53

Reported side effects are also uncommon and usually limited to minor gastrointestinal symptoms, increased urination, and mild allergic reactions. 30 However, severe allergic reactions have occurred occasionally, some of them life threatening. 31 In Australia, one survey found that 20% of allergy-prone individuals were allergic to echinacea.

Other concerns relate to echinacea’s possible immune-stimulating properties. Immunity is a two-edged sword that the body keeps under careful control; excessively strong immune reactions can be dangerous. Based on this concern, echinacea should be used only with caution (if at all) by individuals with autoimmune disorders, such as multiple sclerosis, lupus, and rheumatoid arthritis.

Furthermore, a recent case report strongly suggests that use of echinacea can trigger episodes of erythema nodosum (EN). 36 EN is an inflammatory condition that involves tender nodules under the skin. These nodules often arise after cold-like symptoms. In this report, a 41-year-old man took echinacea on four separate occasions when he thought he was developing a cold, and each time he developed EN instead. When he stopped using echinacea for this purpose, he remained free of EN outbreaks for a full year of follow-up. The cause of EN is not known, but it involves increased activity of certain immune cells; echinacea has been observed to cause similar effects in the same immune cells, suggesting that the relationship is not coincidental.

One study raised questions about possible antifertility effects of echinacea. 32 When high concentrations of echinacea were placed in a test tube with hamster sperm and ova, the sperm were less able to penetrate the ova. However, since we have no idea whether this much echinacea can actually come in contact with sperm and ova when they are in the body rather than a test tube, these results may not be meaningful in real life.

Animal studies of echinacea are supportive of safety in pregnancy. 51,52,54,55 One human study found a bit of evidence that use of echinacea during pregnancy does not increase risk of birth defects, but this evidence is not strong enough to absolutely rely on. 33

Furthermore, studies dating back to the 1950s suggest that echinacea is safe in children. 34 Nonetheless, the safety of echinacea in young children or pregnant or nursing women cannot be regarded as established. In addition, safety in those with severe liver or kidney disease has also not been established.

Two studies suggest that echinacea might interact with various medications by affecting their metabolism in the liver, but the significance of these largely theoretical findings remain unclear. 35, 61 A review of the research literature found no verifiable reports of drug-herb interactions with any echinacea product. 63