Echinacea is a plant native to North America. It's been widely used by indigenous people for the treatment of infections based on their belief in its antiviral and antimicrobial properties. Studies have investigated how echinacea may reduce the risk of upper respiratory infections and complications associated with recurrent respiratory infections. A review of 14 studies found that taking echinacea may lower the risk of developing colds by more than 50% and shorten the duration of colds by one and a half days.