For many years, scientists have debated whether or not echinacea helps banish colds; some studies have suggested a benefit while others have not. Now, a large meta-analysis suggests that the popular herbal remedy really does decrease the incidence and duration of the common cold.

Researchers at the University of Connecticut School of Pharmacy in Storrs examined 14 randomized, controlled clinical trials involving more than 1,300 patients followed for echinacea’s effect on preventing colds and more than 1,600 patients followed for echinacea’s effect on limiting the duration of colds.

The investigators found that the herb decreased a person’s odds of developing a common cold by 58% and reduced the duration of colds by 1.4 days. Moreover, echinacea reduced a person’s chances of catching a cold whether it was taken alone or in combination with other supplements, such as vitamin C, lemongrass, and eucalyptus, among others.

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According to lead author Craig I. Coleman, PharmD, there may be several reasons why other echinacea studies failed to show such benefits. “Other studies may not have been large enough. Also, there are 200 viral strains known to cause colds. Maybe echinacea doesn’t work well against some strains but works great against others.”

Dr. Coleman believes echinacea works by stimulating the immune system. He suggests people start taking it at the first sign of a cold and continue taking it until the cold is gone. “Get a product displaying the ‘USP verified’ mark,” he adds, “and follow package directions” (Lancet Infect Dis 2007; 7:473-480).