Echinacea, the purple coneflower, is the best known and researched herb for stimulating the immune system. Thousands of Europeans and Americans use echinacea preparations against colds and flu, minor infections, and a host of other major and minor ailments. This native American herb has an impressive record of laboratory and clinical research. Thousands of doctors currently use echinacea for treating infectious diseases. Echinacea has a rich tradition of use by North American Plains Indians who used it medicinally more than any other plant. It was prominent in modern American medicine in the early 20th Century, and was discovered by Europeans, who have used it extensively since the 1930s. Today millions of Europeans use echinacea as their primary therapy for colds, flus, infections, and for general immune-boosting effects.