Used as a specific for problems of the mucus membranes, to reduce swelling, inflammation, and infection, and as a very strong blood purifier for serious, toxic blood conditions such as food poisoning, herpes, measles, etc. Goldenseal contains berberine in larger amounts than the Mahonia (Oregon Grape) family. In some studies, berberine showed specific activity against Candida albicans.
It is also used when digestive problems are caused by a lack of activity or tone, or when those tissues are overly relaxed or diseased. Externally, Goldenseal is used for infections and parasitic skin problems.
Some of the problems in using Goldenseal, however, should be mentioned here, as most of the public is unaware of these issues. Goldenseal is such a strong antibacterial that it kills almost all bacteria with which it comes into contact, including the beneficial bacteria of the digestive tract. It also appears to interfere with vitamin B absorption.
More importantly, though, is that Goldenseal is in serious danger of extinction from over-harvesting, as a result of its over- and mis-use for minor infections such as colds. Aside from boosting your immune system and relieving symptoms, which can be accomplished using more sustainable herbs (such as Oregon Grape and Plantain), there is not much that can be done about common, non life-threatening illnesses like colds and flu.
Taking something as powerful and rare as Goldenseal for such ailments is like using chemotherapy for a pimple, and unnecessarily endangers an herb we do need to protect, both for the serious illnesses for which it is helpful, and for its own intrinsic value as a creation of Mother Nature.