Echinacea disappoints: there's still no cure for the common cold.

A folk remedy touted as a cold treatment has failed its most recent--and possibly most exacting--test. Volunteers exposed to a cold virus and given the herbal supplement echinacea fared no better than did virus-exposed participants who received an inert substance, researchers report in the July 28 New England Journal of Medicine.

The U.S. study is the third in 3 years in which echinacea failed to alleviate colds in children or, as in this case, young adults. These findings run counter to earlier reports, most out of Europe, that echinacea revs up an immune response against cold viruses (SN: 3/27/99, p. 207).

For the new study, researchers recruited 399 young adults. Some received drops of Echinacea angustifolia extract and others got placebos. After a week, all volunteers received nasal sprays containing rhinovirus type 39, a common cold virus, and were sequestered in a hotel room for 5 days.

After exposure, volunteers getting echinacea continued to take it. Some participants getting the placebos were switched to echinacea, while others continued with the placebos.

None of it mattered, says study coauthor Ronald B. Turner of the University of Virginia in Charlottesville. More than 80 percent of the people in each group became infected with the virus, and roughly three-fifths of each group showed cold symptoms within a week. The severity of the symptoms also was the same across the groups.

Furthermore, blood tests showed no significant immune boost from echinacea.

While this study tested only E. angustifolia, there is considerable overlap in the chemical constituents of the three purple cone-flower species from which echinacea is derived, says Benjamin Kligler of the Albert Einstein College of Medicine in New York.

Therefore, the new study's findings "might apply to the other Echinacea species as well," says herbal medicine specialist Wallace Sampson of Stanford University.

Echinacea formulations often contain more than one species of the plant (SN: 6/7/03, p. 359). Since the preparations are sold as dietary supplements and not drugs, the Food and Drug Administration doesn't regulate their effectiveness or content.

"Three big negative trials have now come out," says Bruce P. Barrett of the University of Wisconsin-Madison. In the study that he led, reported in 2002, college students with colds fared the same whether they got placebos or a mix of the Echinacea species. In a 2003 report, researchers at the University of Washington in Seattle found that Echinacea purpurea, a common ingredient in formulations, was no weapon against colds in children.

Barrett and Kligler, both physicians, say that they wouldn't discourage people currently using echinacea from continuing to do so, because the supplement is generally safe and may have a significant placebo effect. "But I sure wouldn't go out and tell people who don't believe in it to start taking it," Barrett says.