Isatis

Botanical

What is it

Isatis (Isatis indigotica or Isatis tinctoria), known in Traditional Chinese Medicine as Ban Lan Gen, is a leafy plant whose root and leaf are used for respiratory and viral infections.

Evidence for 2 uses

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

Sore throat / cold symptoms

Limited Evidence

Traditional use is widespread; modern clinical trials are mostly small, short, and of variable quality. Some show symptomatic relief, but evidence is not strong.

Influenza prevention

Mixed Evidence

Laboratory antiviral activity is documented but does not consistently translate to clinical influenza prevention or treatment.

How it works

Isatis contains indirubin, indigo, tryptanthrin, and other indole alkaloids, along with polysaccharides. Laboratory studies suggest these compounds have antiviral, antibacterial, and anti-inflammatory effects, including activity against influenza virus in cell models. In TCM it is used for sore throat, fevers, and 'heat-toxin' patterns. Clinical evidence in humans is limited and largely consists of small Chinese-language trials. Mechanisms in vivo remain incompletely defined.

Dosage

Traditional decoction uses 9-15 g dried root daily. Standardized extracts vary; product labels typically suggest 500-1500 mg/day.

When and how to take it

TCM use is typically short courses (a few days) at the first sign of upper respiratory symptoms, divided into two or three doses with water.

2 commercial forms

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

Ban Lan Gen (root) granules or decoction

Most common TCM preparation.

Traditional water extraction; bioavailability not formally characterized.

Isatis leaf extract (Da Qing Ye)

Used similarly to the root in TCM.

Alkaloid-rich; concentrations vary.

Safety

Generally tolerated short-term in traditional use. Reported side effects include gastrointestinal upset and rare allergic reactions. Long-term safety data is sparse. Some isatis products have been adulterated; quality varies.

Who should be cautious

Avoid during pregnancy and breastfeeding due to lack of safety data. People with autoimmune conditions or on immunosuppressants should consult a clinician. Discontinue if rash or stomach upset occurs.

Interactions

Few documented interactions in clinical literature. Theoretical concern with immunosuppressants given proposed immunomodulatory activity. Caution with other antiviral or anticoagulant therapies until more data exist.

Frequently asked questions

Does isatis cure colds or flu?⌄

No. It is used traditionally to ease symptoms, but clinical evidence does not establish a cure or reliable prevention.

Can I take it daily?⌄

Traditional use is short-term during acute symptoms, not as a daily preventive.

References

Isatis on Wikidata — Wikidata link

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

Research on Isatis (PubMed search) — PubMed link

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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.