Ask a group of people at a cocktail party what you should take if you feel a cold coming on and chances are at least one person will recommend echinacea . Echinacea, also known as purple coneflower, has long been a popular cold remedy in the United States. And it is currently the primary remedy for minor respiratory infections in Germany.

And yet, studies of echinacea for the common cold have had mixed results. Part of the reason for this may be the variety of echinacea preparations that have been tested. To begin with, there are three varieties of echinacea that have been used in cold remedies. In addition, the effectiveness of echinacea may be affected by the part of the plant used, the method used to extract the “active” material, where the plant was grown, and the time of the year it was harvested.

In an effort to study echinacea remedies more systematically, researchers created three carefully defined preparations of Echinacea angustifolia , which they then tested for their effectiveness in the prevention and treatment of the common cold. Their results are published in the July 28, 2005 New England Journal of Medicine. The researchers found that none of the three echinacea preparations they tested fared better than placebo at preventing a cold, or reducing the symptoms of one.

About the Study

The researchers created three preparations from a single lot of the root of the echinacea species Echinacea angustifolia . The preparations varied based on the way the echinacea root was extracted from the plant.

Four hundred and thirty seven healthy volunteers were then recruited and assigned to one of three groups:

Prevention : Participants received the equivalent of 300 milligrams (mg) of one of the three echinacea preparations three times a day from seven days before researchers exposed them to the cold virus (rhinovirus type 39) until five days after exposure to the cold virus.

Treatment : Participants received a placebo for seven days before researchers exposed them to the cold virus, and then received the equivalent of 300 mg of one of the three echinacea preparations three times a day for five days after exposure to the cold virus.

Control : Participants received a placebo three times a day from seven days before researchers exposed them to the cold virus until five days after exposure to the cold virus.

Neither the study subjects nor the research staff knew who was taking an echinacea preparation and who was taking a placebo.

Once the volunteers were exposed to the cold virus, they submitted a nasal wash sample every morning. They also rated their symptoms of sneezing, runny nose, stuffiness, sore throat, cough, headache, malaise, and chilliness on a scale of 0 to 4, every morning and evening for five days.

To test the preventive value of echinacea, the researchers compared the number of participants in each of the three prevention groups who caught a cold to the number in the control group who caught a cold.

To test the treatment value of echinacea, the researchers compared the total symptom scores of each of the three treatment groups to the total symptom score of the placebo group.

The Findings

None of the three echinacea preparations taken before exposure to the cold virus significantly reduced the number of colds caught by participants, compared to placebo.

None of the three echinacea preparations taken after exposure to the cold virus significantly reduced cold symptoms compared to placebo, judging by either the total symptom score or the proportion of study subjects with clinically defined colds. Echinacea also failed to significantly reduce the severity of any individual cold symptom compared to placebo.

One limitation of this study was that researchers did not look at whether echinacea taken before exposure to the cold virus reduced the severity of cold symptoms in volunteers who did come down with a cold. They also did not vary the dosage of echinacea given to the subjects or the source original plants they used.

How Does This Affect You?

In this meticulously designed study, echinacea was no more effective than placebo in preventing or reducing the symptoms of the common cold.

It is possible, of course, that these results only apply to the specific preparations of echinacea tested in this study. Other species of echinacea, echinacea extracted by different methods, echinacea derived from parts of the plant other than the root, or echinacea cultivated in other geographic locations during a different time of year may be more effective in fighting colds. Only more studies will tell, though given the definitive results of this study, it may become more difficult for researchers to obtain federal funding for further work on echinacea.

The good news is that the volunteers taking echinacea in this study did not report significantly more adverse effects than volunteers taking placebo. So if you’ve had positive experiences with echinacea in the past, you may wish to continue taking it. To be on the safe side, however, let your doctor know that you’re taking echinacea, since herbal supplements can interact dangerously with conventional medications, and this herb is no exception.