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Herb library · Herb · Tanacetum vulgare

Tansy

A European roadside plant with flat golden button flowers and a strong camphor smell, long used for worms and to bring on periods. It contains thujone, a nerve poison, and its oil has killed people. It has not been studied in people.

Serious warning

Tansy contains thujone, a nerve toxin. The European Medicines Agency records severe poisonings in people, with convulsions, unconsciousness and death, from thujone-rich essential oils, and King's American Dispensatory (1905) describes deaths from oil of tansy.

Traditional use

Native to Europe and brought to North America by settlers. Old herbals record it given for worms and to bring on menstruation, and its oil was taken, dangerously, to try to end pregnancies. Eclectic physicians used small doses of the cold tea as a bitter for poor digestion and applied the herb as a hot compress. King's American Dispensatory (1905) opens its section on tansy with an account of deaths from the oil.

What studies show

  • Insufficient

    Worms, digestion and periods: no study of tansy on its own in people was found. The research on it is lab and animal work; one trial in people tested it only as part of a three-herb mixture.

Be careful of

Cautions

  • NoteNever take tansy oil. Tansy contains thujone; EU regulators record severe poisonings, convulsions and deaths from thujone-rich essential oils, and set a limit of about 6 mg of thujone a day from herbal medicines.
  • PregnancyDo not use tansy in any form if you are or may be pregnant, or while breastfeeding. King's American Dispensatory (1905) records that its oil was used to try to end pregnancies and calls that use highly dangerous and generally ineffectual.
  • AllergyTansy is in the daisy family; people allergic to ragweed, chamomile or feverfew may react to it.
  • ConditionPeople with seizure disorders should avoid it: thujone causes convulsions.
  • Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.

From the old books

What herbals and dispensaries of the past printed. History, in their words.

“Oil of tansy is a poisonous agent, killing by coma and asphyxiation. The effects are different according to the amount taken.”
Harvey Wickes Felter and John Uri Lloyd, King's American Dispensatory (1905), vol. 2, p. 1913. See the page of King's American Dispensatory, vol. 2, p. 1913 (opens in a new tab) · Read the full passage from King's American Dispensatory, vol. 2, p. 1913

Sources

  1. Public statement on the use of herbal medicinal products containing thujone (EMA/HMPC/732886/2010 Rev.1) (opens in a new tab) · EMA · read September 25, 2026
  2. Therapeutic effects of Rosa canina, Urtica dioica and Tanacetum vulgare herbal combination in treatment of tinnitus symptoms (Clin Otolaryngol, 2023) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
  3. Toxic essential oils. Part V: thujones and thujone-containing essential oils (Food Chem Toxicol, 2017) — PubMed record (opens in a new tab) · NIH · read September 25, 2026

Reviewed September 25, 2026.