For centuries, echinacea has been used to treat and prevent the common cold, as well as other maladies. But now, researchers say that the herb does not significantly shorten or lessen the severity of symptoms with the common cold. But does this mean we should stop using it?

It’s possible, the authors say, that in a larger follow-up study, different results would be seen, with severity potentially reduced by 20% and length reduced by up to 24 hours.

Researchers studied 719 people, aged 12-80, who were suffering from colds. They gave some of the participants echinacea (and told them what it was); they gave other participants either echinacea or placebo, but did not tell them what they were taking. A fourth group of cold sufferers got no treatment at all. By devising these four treatment groups, the researchers could tell whether the effect, if any, was due to the echinacea itself or simply the placebo effect.

The participants rated their cold symptoms twice a day; the researchers also measured two markers for immune response and inflammation.

The researchers found that for people taking echinacea, the symptoms of their colds were reduced by an average of 10%. Their colds also lasted about half a day less than other groups. While the echinacea did have a slight effect, the differences were not statistically significant, meaning that they could theoretically be due to chance, rather than real effect. (If you were wondering, even people taking placebo reported less severe colds than people in the "no treatment" group.) The measures of immune response and inflammation also pointed to a slight benefit in people taking echinacea, but again, the results were not statistically significant.

There were no differences in side effects across the groups, though people not taking any kind of treatment did report slightly more headaches than the other three groups.

However, because the half-day reduction of the length of colds was only an average, some people found more considerably more relief. So it’s possible, the authors say, that in a larger follow-up study, different results would be seen, with severity potentially reduced by 20% and length reduced by up to 24 hours.

The authors write that according to their previous work, most people (3 out of 4) don’t feel that a half-day reduction in their colds is worth it. Still, they say that because they were unable to draw definitive conclusions about the benefits of the remedy, more research will be needed still to determine whether taking echinacea is worthwhile. The study may be slightly limited by its sample size, which was just over 700 participants.

While the jury is still out on the efficacy of echinacea, it’s likely a safe way to treat the common cold, particularly if you believe it works. It’s important to talk to your doctor before adding any kind of supplement to your diet.

The research was carried out by a team at the University of Wisconsin, Madison, and published in the December 20, 2010 issue of Annals of Internal Medicine.