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Viral Upper Respiratory Infections (Colds and Influenza) and Echinacea

Read more about Echinacea.


Until the 1930s, echinacea was the number one cold and flu remedy in the United States. It lost its popularity with the arrival of sulfa antibiotics. Ironically, sulfa antibiotics are as ineffective against colds as any other antibiotic, while echinacea does seem to be at least somewhat helpful. In Germany, echinacea remains the main remedy for minor respiratory infections.

Echinacea has shown promise for reducing the symptoms and duration of colds and aborting a cold once it has started. However, echinacea does not appear to be helpful for preventing colds, except in athletes (see Research Evidence). (Ginseng has shown strong prevention potential.) It may also not be effective in children.

Effect of Echinacea on Viral Upper Respiratory Infections (Colds and Influenza)

Echinacea is generally thought to work by temporarily stimulating the immune system, although most (but not all) recent evidence has tended to cast doubt on this belief.104-105, 145-146 Contrary to popular belief, however, there is little reason to believe that echinacea strengthens or "nourishes" the immune system when taken over the long term. In other words, echinacea is effective for treating but not preventing illness.

Research Evidence on Echinacea

A signficant amount of research has been conducted to investigate the role of echinacea in preventing and treating the common cold.

##Reducing the Symptoms and Duration of Colds

Double-blind, placebo-controlled studies enrolling a total of more than 1,000 people have found that various forms and species of echinacea can reduce the symptoms and duration of a common cold, at least in adults.14-21,115,145

For example, in one double-blind, placebo-controlled trial, 80 individuals with early cold symptoms were given either E. purpurea extract or placebo.22 The results showed that individuals who were given echinacea recovered significantly more quickly: in just 6 days among the echinacea group versus 9 days among the placebo group.

Another double-blind, placebo-controlled trial looked at reduction of the severity of cold symptoms.23 The results in 246 participants showed that treatment with E. purpurea significantly improved cold symptoms such as runny nose, sore throat, sneezing, and fatigue. Symptom reduction with E. purpurea was also seen in a double-blind, placebo-controlled study of 282 people.115

In addition, three double-blind, placebo-controlled studies enrolling a total of about 600 participants found similar benefits with a combination product containing E. purpurea and E. pallida root, along with wild indigo and white pine.106-107,140-141

While the above evidence tends to suggest that the above-ground portion of E. purpurea is active against the common cold, two studies have failed to find benefit. One of these was a double-blind, placebo-controlled study enrolling 120 adults,116 the other an even larger trial (407 participants) involving children.117 The reason for these negative outcomes is not clear. E. angustifolia root has also failed to prove effective in a large study.148

##Aborting a Cold

A double-blind study suggests that echinacea can not only make colds shorter and less severe, it might also be able to stop a cold that is just starting.24 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. Echinacea shows the most prevention promise for post-exercise infections.160 (Glutamine and vitamin C are also helpful for this specific purpose.)

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.25 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.26 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.27)

Four other studies also failed to find statistically significant preventive effects.90,91,118,169

A study often cited as evidence that echinacea can prevent colds actually found no benefit in the 609 participants taken on whole.92 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.119 In this double-blind, placebo-controlled study, 430 children ages 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 of the components of this mixture was responsible for the apparent benefits seen.

How to Use Echinacea

There are three main species of echinacea: Echinacea purpurea, Echinacea angustifolia, and Echinacea pallida. A mixture containing all the parts of E. purpurea above the ground (flowers, leaves, stems) has the best supporting evidence for effectiveness in treating colds and flus;147 the root of E. purpurea is probably not effective, while the root of E. pallida may be the active part of that species.

Side Effects and Warnings

#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. ^[1] Reported side effects are also uncommon and usually limited to minor gastrointestinal symptoms, increased urination, and mild allergic reactions. ^[2] However, severe allergic reactions have occurred occasionally, some of them life threatening. ^[3] 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). ^[4] 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. ^[5] 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. ^[6] 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. ^[7] Furthermore, studies dating back to the 1950s suggest that echinacea is safe in children. ^[8] 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. ^[9] A review of the research literature found no verifiable reports of drug-herb interactions with any echinacea product. ^[10]


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