Echinacea May Not Be Effective for the Common Cold
by Laurie Barclay, MD

June 15, 2004 — Echinacea may not be effective for the common cold, according to the results of a randomized, double-blind trial published in the June 14 issue of the Archives of Internal Medicine. However, the investigators suggest that more studies of different preparations and doses may be needed to validate previous claims.

“Echinacea purpurea stimulates the immune response and is promoted to reduce symptom severity and the duration of upper respiratory tract infections,” write Steven H. Yale, MD, and Kejian Liu, PhD, from Marshfield Clinic Research Foundation in Wisconsin. “Previous research suggests that Echinacea may be most effective at lessening the severity and duration of the common cold when taken early in the illness, and has little to no preventative benefit.”

Within 24 hours of cold symptom onset, 128 patients were enrolled and randomized to receive either 100 mg of E. purpurea as freeze-dried pressed juice from the aerial portion of the plant, or a lactose placebo three times daily until cold symptoms were relieved or until the end of 14 days, whichever came first. At enrollment, the groups were similar in sex and age distribution, time from symptom onset to enrollment in the study, average number of colds per year, and smoking history.

There was no difference between groups for either total subjective symptom scores (P range, .29 - .90) or mean individual symptom scores (P range, .09 - .93) for sneezing, nasal discharge, nasal congestion, headache, sore or scratchy throat, hoarseness, muscle aches, or cough. The time to resolution of symptoms was also similar in both groups (P = .73).

The major study limitation, as with earlier studies, is the modest sample size, whicht may not be large enough to detect a smaller treatment effect of Echinacea.

“Some studies have concluded that Echinacea effectively reduces the symptoms and duration of the common cold. We were unable to replicate such findings,” the authors write. “Further investigation would be necessary to determine whether the dosage and composition (flower, leaves, roots, and/or a combination of species) can be adjusted to produce an immunostimulation that might be adequate to eliminate a viral challenge presented by the organisms responsible for the common cold.”

The Marshfield Clinic Research Foundation in Wisconsin was supported this study. The authors report no relevant financial interest in this article.

Arch Intern Med. 2004;164:1237-1241