Echinacea (Echinacea purpura ) is a medicinal herb originally used by North American Plains Indians. In the 1870s, an enterprising Nebraska doctor began touting it as a blood purifier capable of curing everything from headache and rheumatism to syphilis and hemorrhoids. Commonly known as the purple coneflower after the large purple blossom that crowns its three-foot stalk, this member of the daisy family is a popular, though still controversial, herbal remedy today in this country and abroad. Two other varieties of echinacea are also commonly used, Echinacea pallida (narrow-leaf purple coneflower) and Echinacea angustifolia (pale purple coneflower). As yet, nobody knows exactly how echinacea might boost the immune system and keep infections at bay. Unlike a vaccine that protects you from a specific disease, echinacea seems to increase the overall activity of infection-fighting cells. The herb may stimulate white blood cells and lymph cells to attack viruses, bacteria, and abnormal cells. Some research also suggests echinacea gets the body to make more proteins which alert the immune system to defend against bacterial infection.