Does echinacea prevent colds?

The herbal remedy echinacea gets a lot of attention for its claims to prevent colds and flu or for minimizing symptoms if one develops. However, most studies on this herb find no benefits when it comes to preventing either colds or flu. Studies do find, however, that using echinacea at the beginning of a cold can reduce the length and intensity of the illness. Because there are no standards or quality controls available for supplements like echinacea (including what part of the plant is used in the supplement), and that some supplements may cause toxic side effects in large doses, you should always discuss natural remedies with your healthcare professional before taking them.
Today, retail sales for echinacea to treat and prevent the common cold top $40 million annually. Echinacea was originally used by Native Americans to treat burns and snakebites. Unfortunately, since it has never been proven in good scientific studies to make a difference beyond the placebo affect, the only ones who benefit from echinacea are the companies that sell it. 
Anthony L. Komaroff, MD
Internal Medicine
An ocean of ink has been spilled extolling echinacea as an "immune stimulant," usually in terms of its purported ability to prevent or limit the severity of colds. In 2007, the journal Lancet Infectious Diseases published a review of more than 700 studies concluding that echinacea reduced the risk of catching a cold by 58% and may limit its duration. But this was not a direct study to test effectiveness. Two years earlier, The New England Journal of Medicine reported that direct tests of echinacea's ability to prevent colds found it lacking. In this case, researchers divided a group of 437 people into two groups. For seven days, one group received 900 grams of Echinacea angustifolia each day, and the other received a placebo. At the end of the week, both groups were exposed to a nasal spray containing a cold virus. The researchers found that the echinacea had no effect on whether volunteers became infected with the cold virus or on the severity or duration of symptoms among those who developed colds. Even in children, echinacea doesn't help reduce the duration and severity of cold symptoms, concluded a well-designed study by pediatricians at the University of Washington in Seattle.

Most doctors do not recommend taking echinacea to prevent or cure cold or flu. Also, people with ragweed allergies should be aware that they are more likely to have a reaction to echinacea, and there have been cases of anaphylactic shock. Injected echinacea in particular has caused severe reactions.

Long-term use of echinacea does not ward off influenza or the common cold. A randomized placebo-controlled prevention trial among 108 persons with a history of frequent colds did not demonstrate a difference in the rate of occurrence or in the duration of new colds.

Two subsequent trials also failed to find a preventive effect. In one study, 302 healthy volunteers were given echinacea extract or placebo for 12 weeks. In the other study, 109 patients with a history of more than three colds or respiratory infections in the preceding year were given echinacea extract or placebo for eight weeks. In both studies, there was no advantage to taking echinacea extract.

This commonly held belief seems to be more myth than fact.

A study of over 700 individuals in the Annals of Internal Medicine failed to prove that the herb echinacea prevented getting a cold compared to those getting a placebo or no treatment. Results are mixed as to whether the herb can reduce the duration or the severity of cold symptoms. 

A big problem with using echinacea is that the available supplements on the market vary greatly between the nine different types of the herb as well as the various parts of the plant used in the product. Some individuals may also experience side effects such as intestinal discomfort, rashes, increased asthma, and a life-threatening allergic reaction after consuming echinacea.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.