Principal Proposed Uses - Not recommended for internal use. Blue
flag, a member of the iris family, is found throughout North
America. It was widely used by Native Americans for digestive
problems. In the nineteenth century, physicians of the Eclectic
school of medicine also used blue flag for digestive problems,
as well as to treat thyroid enlargement, enhance immunity,
stimulate the liver, and “detoxify” the body. A topical
preparation of the herb was used for impetigo (a skin infection
caused by bacteria). The rhizome (underground stem) is the part
used medicinally. Blue flag has undergone no meaningful
scientific study. In view of the lack of documented benefits,
the absence of toxicity studies, the toxicity of related
species, and the known side effects, we recommend against the
use of this herb. What Is Blue Flag Used for Today? Blue flag is
used by some herbalists today to treat liver problems and skin
diseases. However, there has been essentially no scientific
evaluation of the efficacy of this herb.