Prophylactic use does not have a significant impact on the frequency, severity, or duration of upper respiratory infection.
Treatment of upper respiratory infection may have a modest positive effect.
Adverse effects are extremely rare.
Trials have found no reductio in the frequency of colds when taken to prevent colds, although exploratory meta analysis suggests Echincea products may be associated with a small reduction in cold incidence (Karisch-Volk M et al).
In treatment trials no association with shorter duration of colds.
Most common adverse effects are: headache, nausea and bad taste.