Blue Flag

Parts used and where grown: The rhizome, or underground stem, of the blue flag (indicating its showy blue flowers) is used medicinally. Blue flag and closely related species (particularly Iris missouriensis, western blue flag) grow across North America.

Blue flag has been used in connection with the following conditions (refer to the individual health concern for complete information):

Rating	Health Concerns
	Impetigo (topical)
Reliable and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit. An herb is primarily supported by traditional use, or the herb or supplement has little scientific support and/or minimal health benefit.

Historical or traditional use (may or may not be supported by scientific studies): Based on Native American traditions, Eclectic physicians (19th century doctors who relied on herbs) and herbalists used blue flag for a number of conditions. Of note was its use as a nonspecific immune enhancer, as a laxative, and to detoxify the intestinal tract.¹ Topical application of fresh, sliced rhizomes to the sores of impetigo (a common bacterial skin infection in children) has been recommended by herbalists.² Traditional herbalists have used blue flag to treat poor digestion characterized by fat malabsorption.

Active constituents: The resinous fraction of blue flag contains numerous phenolic glycosides. Traditional herbal texts suggest these constituents stimulate the parasympathetic nervous system, leading to production of bile, saliva, and sweat.³ However, modern clinical trials have not confirmed these effects for blue flag.

How much is usually taken? Herbalists sometimes recommend up to 10 drops of tincture of the dried rhizome be taken three times per day.⁴ The tea form is unlikely to be effective, since the active compounds in blue flag are not water soluble.

Are there any side effects or interactions? Blue flag can cause nausea, vomiting, and loose stools if too much is taken.⁵ People should not exceed the recommended amount given above. Fresh rhizome should only be applied topically and never taken internally, since it can irritate the mouth⁶ and is much more likely to cause nausea and diarrhea. Blue flag should only be taken on the advice of a physician or herbalist trained in its use. Blue flag is unsafe for use during pregnancy or breast-feeding. People should not give blue flag to children.

At the time of writing, there were no well-known drug interactions with blue flag.

References:

1. Ellingwood F. American Materia Medica, Therapeutics and Pharmacognosy, 11th ed. Sandy, OR: Eclectic Medical Publications, 1919, 1998, 312–3.

2. Moore M. Medicinal Plants of the Mountain West. Sante Fe: Museum of New Mexico Press, 1979, 39–40.

3. Moore M. Medicinal Plants of the Mountain West. Sante Fe: Museum of New Mexico Press, 1979, 39–40.

4. Ellingwood F. American Materia Medica, Therapeutics and Pharmacognosy, 11th ed. Sandy, OR: Eclectic Medical Publications, 1919, 1998, 312–3.

5. Ellingwood F. American Materia Medica, Therapeutics and Pharmacognosy, 11th ed. Sandy, OR: Eclectic Medical Publications, 1919, 1998, 312–3.

6. McGuffin M, Hobbs C, Upton R, Goldberg A (eds). American Herbal Product Association’s Herbal Safety Handbook. Boca Raton, FL: CRC Press, 1997, 64.

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over-the-counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2003.