Treatment of Colds with a Capsule Form of the Herb Echinacea

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The summary below is from the full report titled "Treatment of the Common Cold with Unrefined Echinacea. A Randomized, Double-Blind, Placebo-Controlled Trial." It is in the 17 December 2002 issue of Annals of Internal Medicine (volume 137, pages 939-946). The authors are BP Barrett, RL Brown, K Locken, R Maberry, JA Bobula, and D D'Alessio.

What is the problem and what is known about it so far?

The common cold is one of the most frequent human illnesses. Many different viruses cause colds. No "cure" for the common cold exists, but people use a variety of treatments to try to decrease the bothersome symptoms of colds. Echinacea is an herb that some claim is helpful in treating colds. However, it is uncertain whether echinacea is truly beneficial in treating colds.

Why did the researchers do this particular study?

To find out whether people who begin taking echinacea soon after cold symptoms start have symptoms that are less severe and last for a shorter time than people who do not take echinacea.

Who was studied?

148 students at the University of Wisconsin, Madison, Wisconsin, who had cold symptoms.

How was the study done?

Using posters, newspaper advertisements, and e-mail messages, the researchers recruited students to call at the first sign of cold symptoms. Students could participate in the study if they were 18 years of age or older, had cold symptoms that began within the past 36 hours, and reported at least 2 of 15 listed symptoms. They could not participate if they were pregnant; had certain medical illnesses such as asthma; or were taking antibiotics, antihistamines, or decongestants. The researchers then assigned students to receive either a capsule form of echinacea or a placebo (four tablets six times per day for the first day, then three times per day until cold symptoms resolved or 10 days had passed). The echinacea capsules were made of whole unrefined plant material (a combination of roots from Echinacea angustifolia and herbs and roots from Echinacea purpurea). The placebo looked and tasted like the echinacea capsules but contained no active ingredients. On each day of the study, students completed a detailed questionnaire about the presence and severity of cold symptoms on that day. The researchers then compared the time until all cold symptoms had resolved and the severity of 15 separate cold symptoms (dry cough, sore throat, runny nose, etc.) on each day of the study.

What did the researchers find?

The echinacea capsules had no effect. The duration and severity of cold symptoms were similar in the two groups. Colds lasted an average of about 6 days in each group.

What were the limitations of the study?

This study used a capsule form of echinacea; many other forms of echinacea are sold as cold remedies. In addition, the participants were young, healthy adults, and the results may not apply to older, less healthy people. Even though the researchers aimed to include only people whose symptoms had started less than 36 hours before entering the study, 10 students had symptoms that began more than 36 hours before starting echinacea. This could have hidden a benefit of echinacea taken shortly after symptoms begin.

What are the implications of the study?

A capsule form of echinacea did not benefit young, healthy adults with symptoms of the common cold.