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):
Science Ratings
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. For an herb, supported by traditional use but minimal
or no scientific evidence. For a supplement, 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 (To view, roll mouse over the "References" heading; to hide, click on the heading)
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.
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 June 2009.
Reliable
and relatively consistent scientific data showing a substantial health benefit.
Contradictory, insufficient, or preliminary studies
suggesting a health benefit or minimal health benefit.
