Echinacea for the common cold
Clinical bottom line:
The beneficial effects of Echinacea for the early treatment of colds were modest. There was no convincing evidence of its effectiveness in the prevention of colds.
Three species of Echinacea are used in medicine: purpurea, angustifolia and pallida. It contains flavonoids, glycoproteins and a variety of other active components which are thought to stimulate the immune system. Extracts can be derived from the whole plant, roots or flowers and other plant extracts or homeopathic compounds may be added.
Barrett B, Vohmann M, Calabrese C. Echinacea for upper respiratory infection. Journal of Family Practice 1999; 48: 628-635.
Date review completed : Last search 1998
Number of trials included : 13
Number of patients : Treatment 1264 / Prevention 1152
Control group : Placebo (or vitamin C)
Main outcomes : Symptoms and signs of upper respiratory infection; flu-like symptoms; incidence of upper respiratory infection.
Inclusion criteria were randomised, double blind, placebo controlled trials which assessed Echinacea in the treatment of upper respiratory infections.
MEDLINE and other unspecified bibliographic databases were searched for relevant trials.
Thirteen trials were included; nine assessed the treatment of colds with Echinacea and four assessed prevention. The studies assessed a number of different Echinacea compounds. Studies were too diverse to pool data in a meta-analysis.
Treatment (1264 patients):
The studies assessed patients over different durations (e.g. 8 days to resolution of symptoms). Six trials showed modest, but significant improvement in symptoms over placebo (or vitamin C).
Prevention (1152 patients) :
Three of the four trials showed no significant benefit of using Echinacea over placebo for cold prevention over 8-12 weeks.
Few adverse effects were reported and none were serious.
The beneficial effects of Echinacea for the early treatment of colds were modest and there was no convincing evidence of its effectiveness in the prevention of colds. The trials were generally of medium to poor quality, though they were mostly of reasonable size (over 100 patients per group). The reviewers noted that care should be taken if using Echinacea in pregnant women, infants and children since these groups were excluded from the trials. A Cochrane review  which included unblinded studies was published in 1998. The review by Barrett and colleagues was chosen in preference because it included only double blind studies and assessed four trials published after completion of the Cochrane review.
 Melchart D, Linde K, Fischer P, Kaesmayr J. Echinacea for preventing and treating the common cold (Cochrane Review). In: The Cochrane Library, Issue 3, 2000. Oxford: Update Software.
Identifier 6812 ECHINACEA FOR THE COMMON COLD: Apr-2001