Clinical Question: Is Echinacea purpurea effective in the treatment of cold symptoms?
Setting: Outpatient (any)
Study Design: Randomized controlled trial (double-blinded)
Synopsis: This study evaluated the effectiveness of a freeze-dried extract prepared from the above-ground parts of the E. purpurea plant. All formulations of Echinacea are not the same: two different species are in common use—E. purpurea and Echinacea angus-tifolia—and different parts of the plant, such as the whole plant, roots, or upper parts, are used to make extracts. The participants in this study were solicited by advertisements. The investigators enrolled 128 adults, primarily women, 38 years of age on average, within 24 hours of the onset of cold symptoms. Only 10 percent were smokers. The average duration of symptoms was 15 hours.
The patients were randomized to receive placebo or Echinacea in a dosage of 100 mg three times daily for as long as they had symptoms, up to 14 days. The patients were asked not to take other symptom-relief products, except acetaminophen. Daily symptom scores, which consisted of four points on each of eight symptom scales (e.g., nasal discharge, cough), did not differ at any time between the two groups. The time to complete resolution of symptoms also was not shortened with the use of Echinacea. The study was large enough to find a 25 percent difference in symptoms or a three-day difference in duration.
Bottom Line: Use of a product containing the freeze-dried extract of the above-ground part of E. purpurea is ineffective in decreasing the duration or severity of the common cold. These results contradict findings of two meta-analyses that documented some benefit with other extracts. (Level of Evidence: 1b–)