Question: Will echinacea help prevent or shorten the length of a cold?
Answer: There's really no good evidence that echinacea either prevents a common cold illness or has any effect on the severity of symptoms or duration of symptoms once you have the illness. There have been a number of studies of echinacea. Some have purported to show some modest benefit. However, I think the weight of the evidence is that Echinacea has no benefit, either on incidence of illness or severity of illness.