Tansy

Tanacetum vulgare

Family: Asteraceae Part used: Leaves and flowering tops

Key Compounds

• Thujone (alpha- and beta-)
• Camphor
• Borneol
• Chrysanthenone
• Parthenolide
• Luteolin
• Quercetin
• Chlorogenic acid
• Caffeic acid
• Tannins

Traditional Use

• Insect repellent — the safest contemporary application; thujone, camphor, and borneol are effective insect deterrents, particularly for flies, fleas, and ants; dried herb sachets hung in wardrobes or placed near windows repel flies; fresh sprigs strewn in doorways and on floors (the old strewing herb use); the concentrations of thujone in dried herb sachets are not a systemic concern at normal household exposure; historically used to repel insects from stored food, meat, and corpses; the external insect repellent application is the application with the most favourable risk profile
• Anthelmintic (historical, no longer recommended) — thujone and other volatile compounds have anthelmintic activity against intestinal worms; historical application for threadworms, roundworms, and other intestinal parasites; documented from Dioscorides (1st century CE) through 19th-century pharmacy; the EMA negative assessment reflects that the therapeutic dose required for anthelmintic effect is close to the neurotoxic dose; safer anthelmintic herbs exist (wormwood at lower doses, black walnut); not recommended in contemporary practice
• Emmenagogue (historical, not recommended) — thujone's uterotonic activity was the basis for traditional use for delayed menstruation; the same historical pattern as pennyroyal and wormwood; the abortifacient potential exists at doses close to the therapeutic dose; not recommended in contemporary practice due to the narrow margin; pennyroyal and mugwort have the same issue with better historical documentation; not an appropriate contemporary emmenagogue choice
• Easter food tradition (cultural, historical) — tansy cakes and tansy pudding were eaten at Easter in England from the medieval period through the 18th century; the bitter taste connected to the Passover tradition of eating bitter herbs, transferred culturally into the Christian Easter celebration through medieval syncretism; tansy pudding was a recognised dish in English cookery books; this application reflects the cultural history of the plant rather than a therapeutic use

The name means immortality.

Tanacetum derives from Greek athanasia — immortality. The plant was laid on corpses. The same volatile compounds that deterred insects from living bodies repelled insects from dead ones, slowing putrefaction. Medieval funeral practice used tansy this way. So did ancient Roman practice before it. The preservation application came first; the name followed.

The European Medicines Agency reviewed tansy and concluded the benefit-risk balance is unfavourable for any medicinal use. The margin between a dose that does something useful and a dose that causes seizures is too narrow to recommend it.

The insect repellent still works well. The insects have not read the EMA statement.

Meet the plant

A vigorous perennial growing to 60–150 cm, with distinctive fernlike aromatic leaves and flat-topped clusters of small, bright-yellow, button-like flower heads. The scent is sharp and camphoraceous — immediately identifiable, not entirely pleasant in large quantities. Naturalised widely across Europe, Asia, and North America on roadsides and disturbed ground. Once established in a garden, it is persistent.

The thujone mechanism

Thujone — the primary volatile compound in tansy, constituting up to 70–80% of the essential oil — acts as a GABA-A receptor antagonist. It blocks the receptor that allows inhibitory chloride ions into neurons, increasing neuronal excitability.

The clinical consequences of thujone overdose: nausea, vomiting, convulsions, cardiac disturbance, respiratory depression. The same compound is present in wormwood and was the principal concern about absinthe — with some historical exaggeration about absinthe’s thujone content, but less exaggeration about tansy’s.

The dried herb contains thujone at lower concentrations than the essential oil. The concern is that the dose required for anthelmintic or emmenagogue effect is close enough to the neurotoxic dose that the EMA concluded the margin is insufficient.

The Easter cake tradition

From the 14th to the 18th centuries in England, tansy cakes and tansy pudding were an Easter food. The recipe involved eggs, cream, and fresh tansy leaves — which gave the dish a bitter, camphoraceous flavour and a yellow-green colour.

The practice traces to medieval syncretism: Christian Easter absorbed elements of Passover practice, including the custom of eating bitter herbs (maror). Tansy was available in spring and decidedly bitter. It became the English Easter bitter herb. Robert May’s The Accomplisht Cook (1660) includes tansy recipes. The tradition declined in the 18th century as the bitterness became unfashionable and the plant’s toxic reputation became better understood.

What the safe applications are

Insect repellent (dried herb sachets): Hang dried tansy herb in wardrobes, cupboards, or near windows. Repels flies, fleas, ants, and moths. This is the application with the most favourable risk profile — dried herb in sachets produces volatile exposure that is not systemically significant at household quantities.

Fresh herb (external only): Fresh sprigs in doorways deter flies. Historically used as a strewing herb on floors.

No internal use. The EMA assessment is clear. No essential oil at any dose for any purpose. No tea, no tincture, not for therapeutic purposes.

Could you grow this yourself?

Easily — perhaps too easily. Tansy spreads by rhizome and self-seeds aggressively. In many North American contexts it is considered invasive and is not recommended for garden planting. Where it is already established it requires significant effort to remove. The plant is showy when in flower (the bright yellow button heads in late summer are distinctive) but should be planted, if at all, in a contained bed where its spread can be managed.

Tansy (ヨモギギク) in Japan

Tansy is naturalised in some Japanese regions as an introduced European weed, particularly in Hokkaido and cooler highland areas. It has no traditional medicinal role in Japanese practice. The Japanese name — ヨモギギク (yomogi-giku, ‘mugwort chrysanthemum’) — combines the name for mugwort (Artemisia) and chrysanthemum (Chrysanthemum), reflecting its aromatic and Asteraceae character.

The insecticidal property is noted in Japanese botanical literature in the context of the plant’s invasive character and its historical European use, not as a contemporary medicinal application.

Things you’re probably wondering

Is tansy the same as feverfew? No. Feverfew (Tanacetum parthenium) is in the same genus and has a superficially similar appearance — both are Tanacetum, both Asteraceae. Feverfew’s primary active compound is parthenolide (a sesquiterpene lactone, not thujone), its thujone content is low, and its safety record for short-term internal use at standard doses is acceptable. Feverfew’s traditional use for migraine prevention is the established application. The two plants should not be substituted for each other.

What about tansy ragwort? Tansy ragwort (Jacobaea vulgaris, formerly Senecio jacobaea) is not related to tansy despite the name. It is toxic to horses and cattle through its pyrrolizidine alkaloid content — a completely different toxicity mechanism from tansy’s thujone. It is a common cause of livestock poisoning in Europe and North America. The shared common name is a regional naming accident.

Botanical details

The full compound list

See Also

• Pennyroyal — comparable toxicity profile; thujone family of toxic monoterpenes; EMA negative assessment; insect repellent as safest use
• Mugwort — related Artemisia; similar but lower thujone; safer emmenagogue; Japanese 艾 (yomogi) connection
• Feverfew — same genus Tanacetum; parthenolide not thujone; safe for migraine prevention use

References

• European Medicines Agency. (2010). Public Statement on Tanacetum vulgare L. EMA/HMPC/95008/2008.
• Grieve, M. (1931). A Modern Herbal. Dover.
• Orav, A. et al. (2010). Composition of the essential oil of Tanacetum vulgare from different Estonian locations. Proceedings of the Estonian Academy of Sciences, 59(2), 163–168.
• Gadano, A. et al. (2006). In vitro genotoxic evaluation of the medicinal plant Tanacetum vulgare L. Journal of Ethnopharmacology, 106(2), 172–176.