Goldenseal (Hydrastis canadensis), closely related to the buttercup and similar in appearance, has long been a favorite herbal remedy in Native American communities. Goldenseal is prescribed for digestive issues, bad breath, oral health, against candida, and as an anti-fungal.
Ringworm seems to be another condition against which goldenseal can be effective. Combined with echinacea, it is often taken to prevent or ameliorate cold and flu symptoms.
While goldenseal seems quite safe in general, it does contain alkaloids and for that reason its use with pregnant women and children should be limited or avoided in most cases.