A review of 14 clinical trials found that echinacea reduced the odds of developing a cold by 58% and the duration of a cold by 1 to 4 days. However, some experts dispute these findings claiming there were several weaknesses in the analyses. Echinacea preparations tested in clinical trials differ greatly. It is important to choose a high-quality echinacea supplement, and to use echinacea as early as possible in the course of a cold, with multiple doses per day for the first few days. Talk to your health care provider for recommendations.