Echinacea

The hottest commercial cold product in health food stores and many pharmacies is Echinacea. German researchers have shown that Echinacea can stimulate the immune system. 

It also boosts the body's production of natural killers cells and increases alpha interferon production. Both of these play a critical role in fighting off the viral cold infections. One study in Europe showed that people taking the herb recovered from their cold 4 days earlier than those on the placebo.

There is however some controversy on how long to take it however.

This herb is incredibly popular for growers, and not all products may live up to the expectations of purity. Consumers Union analyzed 12 brands and said there was substantial variability in the purity.

This herb originated in America and was used by the plains Indians; it became very popular in the 19th century and then fell off when antibiotics came out. German researchers then discovered the value and now Americans are catching up again.

Astragalus (Huang Se)

This ancient Chinese herb is rarely mentioned in the US, and yet may be more important in immune modulating. Astragalus has the ability to stimulate production of natural killer cells, macrophages, and many other immune system components to fighting off viral cold infections.

In China, a piece of astragalus root is added to chicken soup to help speed up cold recoveries. Commonly though, it is made into tea. By itself this herb is very safe, but it does interactive with prescription drugs. Hopefully with the natural doctor prescriptions you won't have to worry about that.