t's been said that Asian ginseng boosts the immune system, which might help the body fight off infection and disease. The best evidence is that it may help reduce your risk of getting a cold or flu. Studies have found that ginseng seems to increase the number of immune cells in the blood and improve the immune system's response to a flu vaccine. In one study, 227 people got either ginseng or placebo for 12 weeks, and got a flu vaccine after 4 weeks. The number of colds and flu were two-thirds lower in the group that took ginseng.
Two studies found that ginseng lowered the chance of getting a cold. In one double-blind, placebo-controlled study of 323 people, those who took 400 mg of ginseng daily for 4 months had fewer colds. When they did get a cold, it wasn't as severe and didn't last as long as the people who took placebo.