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Home » Echinacea and the common cold–Myth vs. Science

Echinacea and the common cold–Myth vs. Science

Last updated on November 2nd, 2012 at 11:31 am

It’s getting close to winter once again, so people always recommend their various lotions and potions to either prevent the common cold or, at least, to reduce the course of the disease. Alternative medicine’s favorite disease to treat is the common cold, mainly because it’s an easy disease to handle without too many serious problems. Also, from the patient’s perspective, the length and seriousness of the cold is usually very subjective, since the patient has a difficult time making an accurate determination when the cold started or ended, and making a quantitative assessment of the seriousness of the disease. Moreover,  confirmation bias is usually the reason one hears that something worked for the cold–the person who reports some product works forgets all the times it doesn’t. Or completely misjudges the actual effects of any treatment.

The list of products that you might run across in your local pharmacy that claim to have an effect on the common cold are many. Zinc, oscillococcinum, garlic, and vitamin C. I wrote about these products last winter, and they mostly don’t work. The strangest cold remedy you might find is oscillococcinum, which is a homeopathic preparation derived from duck liver and heart, diluted to 200C, or 200 1:100 dilutions.  In other words, in a liter of water there are precisely no molecules of duck guts. And there isn’t any logical explanation of a possible mechanism that would allow one to conclude that duck offal has an effect on cold viruses. Though Oscillococcinum is supposed to be used for flus, many use it for colds, but it doesn’t matter, why would a diluted potion of duck guts cure any virus? Well, Cochrane Reviews concluded that ”current evidence does not support a preventative effect of Oscillococcinum-like homeopathic medicines in influenza and influenza-like syndromes.


One of the most popular alternative medicine, herbal preventative treatments or cures for the common cold is echinacea, a daisy like flowering plant endemic to central and eastern North America. It’s been familiar to people for 10-20 years, and is really a part of popular culture as part of the cold-season. I never take it, but then again, I’m not gullible.

You might think that echinacea was used by by Native Americans as some herbal medicine, and there is some evidence that it had been. Amusingly, its modern-day use as a cold remedy dates to the 1960’s when a Swiss herbal supplement maker who, during a trip to South Dakota in the 1960s, was erroneously told echinacea was used for cold prevention by Native American tribes who lived in the area. In other words, its current use wasn’t even based on a myth or some legend, but on a mistake. 

So without any basis in fact, history, or even myth, the alternate medicine world tries to make echinacea out to be one of the great cold remedies out there. For example, Evidence-Based Complementary and Alternative Medicine published a study that purported to show that Echinacea has some effect on preventing common colds. Then the press gets ahold of it, which leads to the headlines like: Echinacea ‘can prevent colds’. How do we get from a mistake to a pill that can prevent colds. Well, that’s why we have science.


I’m going to go about this two ways. First of all, let’s take apart this study study, even though I recommend that we should always evaluate primary studies, like the one above, in the broad context of ALL of the peer-reviewed studies on echinacea, a lot of it of much higher quality than the one above. But let’s give it the benefit of the doubt.

Evidence-Based Complementary and Alternative Medicine is a no-impact journal, published by what is considered a “predatory publisher“, one that spams email lists and gets authors to pay to publish their articles. In other words, this is about as much a high quality journal publication as I would publishing a book on Kindle and paying for it myself. And then claiming I’m a published author.

Setting that aside, British National Health Service also analyzed the echinacea cold study claims and found a “number of oddities” that raised doubt over the results. There main points were:

  • The study was part funded by A. Vogel, a Swiss manufacturer of herbal remedies, including echinacea products. In general, I’m not opposed to manufacturers funding studies, but usually they should be published in high quality peer reviewed journals. This wasn’t, making it very suspect.
  • The NHS seemed to determine that “the researchers found no significant difference between the numbers of colds that occurred in the two groups.”
  • There appeared to be no 95% confidence level statistics provided for echinacea vs placebo groups, a standard measure that is nearly always used in clinical trials.
  • The NHS concludes, “It could well be the case that Echinacea may have a role in the prevention or treatment of colds. But, based on the results of this study, it is very hard to state that with any certainty.” In other words, this study doesn’t tell us much at all.
Better studies, of course, are secondary, meta-reviews that are published in high impact, peer reviewed journals. And, as I’ve discussed before, I have a preference for meta-reviews in the Cochrane Collaborations
Here’s a meta-review in the Cochrane Reviews that concluded: “Beneficial effects of other Echinacea preparations, and Echinacea used for preventative purposes might exist but have not been shown in independently replicated, rigorous RCTs (randomized controlled trials.” So that review clearly states that echinacea doesn’t work.
Here’s a study in the very high-impact in the New England Journal of Medicine that concluded: “The results of this study indicate that extracts of E. angustifolia root, either alone or in combination, do not have clinically significant effects on infection with a rhinovirus or on the clinical illness that results from it.”
I’m sure someone will post in the comments one of the half-dozen “peer-reviewed” articles that show echinacea works. But, they are primary research articles that are analyzed in the Cochrane Review, which has concluded that they have not been replicated. 
What the Skeptical Raptor says
There is still little evidence that Echinacea works, and what evidence there was only showed very slight effects. And the facts are that it was sold as a cold remedy based on a mistaken understanding of how Native Americans used it. Don’t waste your money.
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Michael Simpson

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