Echinacea for preventing and treating the common cold.

BACKGROUND: Extracts of the plant Echinacea (family Compositae) are widely used in some European countries and the USA for upper respiratory tract infections. OBJECTIVES: The objective of this review was to assess the effects of preparations containing extracts of Echinacea in the prevention and treatment of the common cold. SEARCH STRATEGY: We searched the Cochrane Acute Respiratory Infections Group and Complementary Medicine Field's trials registers, MEDLINE, EMBASE, Phytodok and reference lists of articles. We also contacted researchers and manufacturers. Date of last search: Spring 1998. SELECTION CRITERIA: Randomised and quasi-randomised trials comparing preparations containing an extract of Echinacea compared with a placebo, no treatment, or another treatment for common colds. DATA COLLECTION AND ANALYSIS: At least two independent reviewers assessed trial quality and extracted data. MAIN RESULTS: Sixteen trials (eight prevention trials, and eight trials on treatment of upper respiratory tract infections) with a total of 3396 participants were included. Variation in preparations investigated and methodological quality of trials precluded quantitative meta-analysis. Overall, the results suggested that some Echinacea preparations may be better than placebo. REVIEWER'S CONCLUSIONS: The majority of the available studies report positive results. However there is not enough evidence to recommend a specific Echinacea product, or Echinacea preparations for the treatment or prevention of common colds.