Blue flag is a species of iris, which commonly grows in moist meadows, marshes, and along stream banks in northern North America. The root or rhizome is the part most often used and is the source of the iridin, also known as irisin. Iridin is usually used as a powdered extract that is bitter and nauseating and has diuretic and laxative properties.
The blue flag rhizome has a very slight but peculiar odor, and a pungent, unpleasant taste. When used internally, fresh blue flag produces nausea, vomiting, purging, and gastrointestinal cramping. The dried root is less acrid and is traditionally employed as an emetic, diuretic, and cathartic. It has also been used for syphilis, some scrofula (tuberculosis infection of the neck lymph glands), skin disorders, and dropsy (edema).
Currently, blue flag is frequently used topically for skin conditions, such as impetigo, eczema, and psoriasis. It is also used for detoxification by increasing urination, stimulating bile production, and acting as a laxative. Various Native American tribes have had many uses for blue flag including for lymphatic or kidney cancer.
There are currently no high quality studies on the medicinal applications of blue flag. Clinical trials are needed to define the efficacy and safety of blue flag.
American blue flag, beta-sitosterol fatty acids, blue flag iris, clajeux (French), dagger flower, dragon flavonoids, flower, flag lilly, flag lily, fleur-de-lis (French), flower-de-luce (French), furfural, gum, harlequin blueflag, Iridaceae (family), iridin, irigenin, Iris caroliniana Watson, Iris versicolor, iris versicolore (French), irisin, isoflavonoids, isophthalic acid, kosatec strakat (Slovak), Lis met Bontkleurige Bloem (Dutch), liver lily, oleoresin, phytosterols, poison flag, purple flag, salicylic acid, sciatica, snake lily, tannin, triterpenoids, water flag, water iris, wild iris.
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.