Siberian ginseng (Eleutherococcus senticosus), has been used for centuries in China and Russia as an "adaptogen." An adaptogen is a substance that helps the body better cope with either mental or physical stress. Siberian ginseng has been traditionally used to increase energy, longevity, and vitality. It is thought to stimulate the immune system and to help prevent colds and flu.
A double-blind study found that a product containing Siberian ginseng combined with andrographis reduced the severity and length of colds when taken within 72 hours of symptoms starting. People with flu taking Siberian Ginseng also saw their symptoms go away faster than those who took amantadine, a common flu medicine.
Other studies found that healthy people who took Siberian ginseng for 4 weeks had more T-cells, which may indicate their immune systems were stronger, and a double-blind study of 93 people with herpes found that taking Siberian ginseng reduced the number of outbreaksi, and that outbreaks that did happen were less severe and didn't last as long. One study also found that middle-aged volunteers who took Siberian ginseng improved their memory compared to those who took a placebo.
For optimum effect it is recommended to take products containing Siberian ginseng for a period of four months, followed by a one month break before recommencing use.