By the early Twentieth century, echinacea had become the best selling medicinal tincture in America, used for a variety of internal and external conditions. But by 1910 it had been dismissed as worthless by the AMA, although it continued to be used. Echinacea fell into disuse in this country in the 1930's. However, Europeans began growing and using echinacea, especially the Germans, and to this day have produced the best scientific documentation of its value. The extract's popularity in the U.S. grew rapidly during the 1980s, and the plant is now again among America's best-selling herb extracts.

The most common anecdotal reports about the use of ecinacea are from people who begin taking the extract at the first sign of a cold. Often to their surprise, they find the cold has disappeared, usually within twenty-four hours, and sometimes after taking the extract only once. Anecdotal evidence carries little weight in scientific circles, but plant drug researchers have conducted over 350 scientific studies about echinacea. Here's what some of those studies say about echinacea:

The most consistently proven effect of echinacea is in stimulating phagocytosis, or the consumption of invading organisms by white blood cells and lymphocytes. To prove this, scientists incubate human white blood cells, yeast cells and echinacea extract. They examine the blood cells microscopically and a count the numbers of yeast cells gobbled up by the blood cells.

Extracts of echinacea can increase phagocytosis by 20-40%. Another test, called "the carbon clearance" test, measures the speed with which injected carbon particles are removed from the bloodstream of a mouse. The quicker the mouse can remove the injected foreign particles, the more its immune system has been stimulated. In this test too, echinacea extracts excel, confirming the fact that this remarkable plant increases the activity of immune system cells so they can more quickly eliminate invading organisms and foreign particles.

As with astragalus, echinacea causes an increase in the number of immune cells, further enhancing the overall activity of the immune system. Echinacea also stimulates the production of interferon as well as other important products of the immune system, including "Tumor Necrosis Factor", which is important to the body's response against cancer.