Tansy (Tanacetum vulgare): Benefits, Dosage, Safety & Evidence

Frequently asked questions

How does tansy work to expel intestinal worms?

Tansy acts as an anthelmintic primarily through its volatile oil component, thujone. This compound acts as a neurotoxin to parasites, effectively paralyzing intestinal worms such as roundworms and pinworms, which allows the body to expel them. Historically, it was followed by a purgative to ensure the parasites were removed before the thujone caused systemic toxicity in the host (Evidence Level: C/Traditional).

Is tansy safe to take during pregnancy?

No, tansy is strictly contraindicated during pregnancy and is considered unsafe. The herb contains thujone, which stimulates uterine contractions and has a historical reputation as an abortifacient. Ingestion can lead to miscarriage or fetal harm. Additionally, the neurotoxic effects of thujone pose significant risks to fetal development. It should be completely avoided by pregnant and nursing women (Evidence Level: C/Traditional).

What is the safe dosage for tansy tea?

Due to the risk of thujone toxicity, tansy should only be taken in very low doses. The standard recommendation for adults is 0.5 to 1 gram of dried herb per cup of boiling water, consumed as a tea. Usage must be short-term, typically limited to a few days, and should not exceed two weeks. The essential oil should never be ingested internally due to high toxicity (Evidence Level: Traditional).

Does tansy interact with any medications?

Yes, tansy has significant interaction potential. Because thujone lowers the seizure threshold, it may counteract the effectiveness of anticonvulsant medications like phenytoin or valproate. It also carries hepatotoxic risks, meaning it should be avoided alongside other liver-straining drugs or alcohol. Furthermore, its potential to affect blood clotting suggests caution when combined with anticoagulants like warfarin (Evidence Level: C/Theoretical).

Why is tansy considered toxic?

Tansy is considered toxic because of its high concentration of thujone, a monoterpene ketone. Thujone is a neurotoxin that can overstimulate the nervous system, leading to seizures, hallucinations, and muscle spasms. Chronic use or overdose can cause irreversible liver damage and liver failure. Historical records document fatalities resulting from attempts to use the herb for abortion, necessitating extreme caution even at low therapeutic doses (Evidence Level: C).

PubMed-compiled information sheet

This sheet was compiled from PubMed (NIH) abstracts using AI assistance. Every factual claim is cited to a real PubMed article (see the source list). It has not yet been human-reviewed — confirm with a healthcare provider before use.

Compiled from 30 PubMed articles · model: gemma4:31b

Summary

Tansy (Tanacetum vulgare) is an herbaceous plant used in folk medicine for various ailments, containing bioactive compounds with antimicrobial and antioxidant properties [PMID:36679141, PMID:36839938].

Background

Tanacetum vulgare is a widespread invasive species in North America and a member of the Asteraceae family [PMID:41124138]. It exhibits significant intraspecific chemodiversity, forming distinct chemotypes based on terpenoid composition [PMID:37703504, PMID:37351733].

Traditional uses

Used in folk medicine for digestive problems, fevers, migraines, parasites, and as an insect repellent [PMID:36679141]. It has also been traditionally applied for headaches, rheumatism, respiratory, and neurological problems [PMID:39683883].

Active compounds

Active substances include essential oils rich in oxygenated monoterpenes and sesquiterpenes [PMID:33244630], specifically alpha-thujone, beta-thujone, eucalyptol, sabinene, chrysanthenon, camphor, and linalool oxide acetate [PMID:37998837]. It also contains phenolic acids (chlorogenic acid, rosmarinic acid), flavonoids (luteolin-7-glucoside, quercetin), and pectin (tanacetan) [PMID:36839938, PMID:40680672, PMID:38190112].

Mechanism of action

The plant's essential oils and phenolic compounds provide antimicrobial and antioxidant activities [PMID:36679141, PMID:37653885]. Quercetin, present in tansy, exhibits anti-inflammatory, antibacterial, and immunomodulatory effects [PMID:40680672].

Clinical evidence

Evidence DCognitive function and anxiety

In rats, a 200 mg/kg alcohol extract improved learning and memory, while a 1000 mg/kg dose resulted in anxiolytic-like behavior [PMID:39683883]

Evidence DIchthyophthirius multifiliis (fish parasite)

Extracts significantly reduced the survival of trophonts and theronts in vitro [PMID:33847089]

Evidence DTrichostrongylidae Nematodes (sheep)

Extracts demonstrated strong larvicidal activity in vitro [PMID:37443974]

Evidence DBacterial infections

Essential oil shows antibacterial efficiency against ESKAPE pathogens [PMID:37998837]

Safety & adverse effects

Tansy can be toxic to livestock [PMID:41124138]. Thujone, found in the plant, is toxic in high concentrations [PMID:37653885]. It is also a known cause of Compositae dermatitis, an allergic contact dermatitis [PMID:12793186, PMID:3827282].

Evidence summary

The available evidence consists primarily of in vitro studies, animal models (rats, mice, bees), and case reports of allergic reactions. There are no human clinical trials provided in the source material.

PubMed sources

1.PMID: 12793186 (2003) — [Compositae dermatitis]. · Medicinski pregled
2.PMID: 36679141 (2023) — Physicochemical and Antibacterial Properties of Alginate Films Containing Tansy (Tanacetum vulgare L.) Essential Oil. · Polymers
3.PMID: 40680672 (2025) — The role of Quercetin in the treatment of kidney diseases: A comprehensive review. · Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie
4.PMID: 37513392 (2023) — Antimicrobial and Apoptotic Efficacy of Plant-Mediated Silver Nanoparticles. · Molecules (Basel, Switzerland)
5.PMID: 41124138 (2025) — Fertilizer and fungicide reduce herbicide efficacy and enhance growth of invasive common tansy (Tanacetum vulgare). · PloS one

Tansy

Sources & Citations

Calculate a safe dose of Tansy

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Frequently asked questions

Summary

Background

Traditional uses

Active compounds

Mechanism of action

Clinical evidence

Safety & adverse effects

Evidence summary

PubMed sources

Government sources

Tansy

Sources & Citations

Calculate a safe dose of Tansy

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Frequently asked questions

Summary

Background

Traditional uses

Active compounds

Mechanism of action

Clinical evidence

Safety & adverse effects

Evidence summary

PubMed sources

Government sources