Blue Flag

Botanical

What is it

Blue flag (Iris versicolor) is a North American wetland iris whose root and rhizome were used in traditional Western herbal medicine for skin conditions, lymphatic support, and digestion.

Evidence for 1 use

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Skin / lymphatic support (traditional)

Mixed Evidence

Traditional use is documented but no clinical trials confirm benefit, and toxicity is well-recognized.

How it works

The rhizome contains iridin (a glycoside), triterpenoids, salicylic acid derivatives, and volatile oils. Traditional herbalists have used it as a 'lymphatic alterative' and choleretic (bile flow stimulant). Some compounds have shown laxative and emetic effects in animal studies, and high doses can cause severe GI symptoms. Clinical human evidence is essentially absent, and modern herbalists generally use blue flag cautiously or not at all.

Dosage

Traditional doses were small (e.g., 1-2 mL tincture). No standardized modern dose exists.

When and how to take it

Traditional internal use is short-term and at low doses, usually in combination formulas. Not a routine supplement.

1 commercial form

Compare the main delivery options and what they’re best suited for.

Dried rhizome tincture

Traditional Western herbal form.

Active compounds extract into alcohol.

Safety

Fresh blue flag rhizome is acrid and can cause severe nausea, vomiting, diarrhea, and skin irritation. Dried, aged material is milder but still potent. Overdose has caused poisoning in livestock and humans historically.

Who should be cautious

Avoid in pregnancy and breastfeeding. Avoid in children, in people with active GI inflammation, or with liver/gallbladder disease. Internal use should only be considered under expert herbalist guidance.

Interactions

Theoretical interactions with diuretics, laxatives, and bile-acting medications. Data are sparse.

Frequently asked questions

Is blue flag safe?⌄

Fresh root is toxic and even dried preparations can cause severe GI upset. Use only under qualified herbalist guidance at low doses.

Is it the same as the garden iris?⌄

Most irises share related toxicities. Blue flag is one specific North American species; ornamental garden irises are not generally used medicinally.

References

Blue Flag on Wikidata — Wikidata link

Blue Flag on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Blue Flag (PubMed search) — PubMed link

Track Blue Flag with Pilora

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.