Echinacea for Preventing and Treating Colds

What is the problem and what is known about it so far?
Echinacea is an herbal remedy available over-the-counter that has enjoyed a resurgence of popularity in the U.S. for both prevention and treatment of the common cold which is most often caused by rhinovirus. In fact, it is the third most commonly used herbal remedy in the country. Several studies have tried to evaluate the effectiveness of Echinacea for both a preventative and treatment for rhinovirus infections but the results have been inconclusive.

Why did the researchers do this particular study?
This study examined whether any of several different preparations of one type of Echinacea are effective for preventing or treating the common cold.

Who was studied?
437 healthy young volunteers who were determined by a blood test to be susceptible to a strain of rhinovirus that would be used in the study to induce a common cold, were recruited from the University of Virginia community.

How was the study done?
These volunteers were divided into groups each treated with different preparations of Echinacea augustifolia or placebo (control group). Participants were followed for 7 days prior to exposure to the rhinovirus and for 5 days afterwards. The rhinovirus was inhaled through the nose in a standardized solution. Some groups were given treatment before and after exposure and some were only treated after exposure, getting a placebo ‘treatment’ beforehand. Neither the persons administering or those receiving the treatments knew which formula was being used. The participant’s symptoms were evaluated with a standardized scoring system. Their nasal secretions were weighed and tallied every 24 hours and nasal swabs were used to evaluate the concentration of inflammatory cells on their nasal mucosa.

What did the researchers find?
The study found that there was no significant reduction in infection rates, symptom severity, or mucosal inflammatory cell levels among the different treatment or the placebo groups.

What were the limitations of the study?
The Echinacea doses used in the study were lower than those commonly used by naturopathic physicians. Also the type of Echinacea used was said to be less effective than Echinacea pallida the most commonly used preparation.

What were the implications of the study?
Based on the careful way in which the dosing and preparations of Echinacea augustifolia were evaluated it is unlikely that this agent is effective at preventing and treating the common cold caused by rhinovirus. The effects of other preparations and dosing need further study.

Summarized by Dan Goodyear, MD, Family Medicine Resident, Fletcher Allen Health Care.
Summarized from "An evaluation of Echinacea angustifolia in experimental rhinovirus infections". Turner R. B. et al., New England Journal of Medicine, July 28, 2005, Volume 353, Number 4, pages 341-348.