The Early Show medical correspondent Dr. Emily Senay says the latest study along those lines isin warding off colds.
Senay points out that there's a wide variety of herbal medicines available over-the-counter, making a variety of health claims.
Among them is echinacea to boost the immune system, Gingko Biloba to improve memory, and St. John's Wort to relieve depression.
These medicines have been largely dismissed by many Western doctors due to a lack of solid proof that they work, Senay observes. But, in recent years, scientists have started putting them to the test in studies with the same standards applied to modern conventional medicine.
The study on echinacea appears in the latest New England Journal of Medicine. Echinacea is a flower prepared in different ways as an herbal remedy to boost the immune system to ward off colds and respiratory infections, Senay explains.
About 400 people were given various combinations of echinacea extract or placebo pills and then exposed to a rhinovirus that causes the common cold.