A: Although most people in the West think of ginseng as a stimulant, in Eastern Europe ginseng is widely believed to improve overall immunity to illness.

A recent study looked at the potential immune-stimulating effects of Panax ginseng when taken by mouth. Four weeks into the study, all participants received influenza vaccine. The results showed a significant decline in the frequency of colds and flus in the group that took ginseng.

While more research is needed, this study suggests that ginseng may be able to do what echinacea, zinc lozenges, and vitamin C cannot: prevent colds.

There are actually three different herbs commonly called ginseng: Asian or Korean ginseng (Panax ginseng), American ginseng (Panax quinquefolius), and Siberian "ginseng" (Eleutherococcus senticosus). (The latter herb is actually not ginseng at all, but some herbalists believe that it functions identically.)

The various forms of ginseng appear to be nontoxic, both in the short and long term, according to the results of studies in mice, rats, chickens, and dwarf pigs. Ginseng also does not seem to be carcinogenic.

Side effects are rare. Occasionally women report menstrual abnormalities and/or breast tenderness when they take ginseng, and overstimulation and insomnia have also been reported. Unconfirmed reports suggest that highly excessive dosages of ginseng can raise blood pressure, increase heart rate, and possibly cause other significant effects.

Safety in young children, pregnant or nursing women, or those with severe liver or kidney disease has not been established.