Echinacea ineffective for the common cold

Echinacea has no effect on the severity or duration of common cold symptoms, according to the results of a recent randomized controlled trial. The trial involved 719 patients (age 12–80 years) with new-onset common cold. Patients were assigned to one of four groups: no pills, placebo pills (blinded), Echinacea pills (blinded) or Echinacea pills (unblinded, open-label). The Echinacea groups received the equivalent of 10.2 g of dried Echinacea root during the first 24 hours and 5.1 g during each of the next four days.

Common cold severity was assessed twice daily by self-reporting, using the short version of the Wisconsin Upper Respiratory Symptom Survey. Secondary outcomes included interleukin-8 levels and neutrophil counts from nasal wash, which were measured at enrolment in the study and two days later.

A total of 713 subjects completed the study. The mean cold severity was 236 for the blinded Echinacea group and 258 for the unblinded Echinacea group, 264 for the blinded placebo group and 286 for the no-pill group. A comparison of the two blinded groups showed a 28-point nonsignificant trend toward benefit for Echinacea. The mean illness duration was 6.34 days in the blinded Echinacea group, 6.76 days in the unblinded Echinacea group, 6.87 days in the blinded placebo group and 7.03 days in the no-pill group. A comparison of the blinded groups showed a nonsignificant 0.53-day benefit for Echinacea. The median changes in interleukin-8 levels and neutrophil counts were not statistically different among the four groups. The frequency of adverse effects was also similar among the four groups.

The authors concluded that statistically significant differences in illness duration and severity were not seen with this dose and formulation of Echinacea compared with placebo. However, a higher-than-expected variability in results limited the study’s power to detect small benefits.

Reference
Barrett B, Brown R, Rakel D, et al. Echinacea for treating the common cold – a randomized trial. Ann Intern Med 2010;153:769-77. www.annals.org/content/153/12/769.full.pdf+html (accessed December 22, 2010).