Blue Flag

Grown throughout North America, the underground stem, or rhizome, of the eye-catching blue flag plant in the iris family was traditionally thought to have medicinal properties. Historically, the plant has been used to treat constipation, dermatitis, and skin disease. Late nineteenth-century medical literature also referenced the plant as an emmenagogue, a type of herb believed helpful for inducing labor, increasing menstrual flow or regulating the menstrual cycle. Blue flag contains furfural, a known mucous membrane irritant. It also contains isophthalic acid, iridin, beta-sitosterol, irigenin, irilone-4'-glucoside, and irisolone-4'-bioside. Iridin reportedly can be poisonous to humans and animals; however, there is some uncertainty as to whether the chemical of that name cited as toxic is identical to the substance found in blue flag.

Blue Flag has no established medical uses, and is not widely used today. However, some herbalists recommend it for skin diseases.

Typical doses of Blue Flag are 0.6 to 2 g of the dried rhizome, or 1 to 2 ml of the liquid extract, 3 times daily.

Safety studies of Blue Flag have not been performed, and related species have been found toxic. It is also said to cause nausea and vomiting when taken at higher doses. For all these reasons, we recommend avoiding blue flag.