Tansy

• Tansy is not safe to swallow, and the oil is the main danger. Tansy contains thujone and, depending on the plant, camphor. The WHO/JECFA monograph says tansy oil causes convulsions, that poisoning signs include vomiting, gastroenteritis, loss of consciousness, heart rhythm problems, bleeding from the gut and hepatitis, and that human deaths have been reported. A consumer reference says people have died after as little as 10 drops of oil and after teas or powders. Details of individual cases could not be traced here (the 1852 case report's text was not read). Authoritative guidance ^{9 21 3}
• Thujone can cause seizures. In animals thujone blocks the GABA-A receptor, the brain's main calming switch, and causes convulsions in a dose-dependent way. The EMA calls thujone a severe neurotoxicant, though some experts rate the human risk lower. How much it takes to cause seizures in people is not known. Thujone content in tansy varies from about 6% of the oil (Bulgarian camphor type) to about half or more (other types), and you cannot tell by looking at a plant or most labels. Animal research ^{8 18 4 11 20}
• Do not use in pregnancy or breastfeeding. A consumer reference says tansy is unsafe in pregnancy because it may bring on bleeding and contractions and can cause miscarriage, and unsafe when breastfeeding. A university extension page says thujone can cause miscarriage and reports abortion in cattle after large amounts. The EMA says there are no studies to assess thujone in pregnant women and children, so exposure in these groups should be minimised. No clinical study was found; the warning rests on reference works and animal reports. Authoritative guidance ^{21 16 4}
• Liver, kidney and bleeding harm are listed in poisoning. The JECFA monograph lists hepatitis and gut bleeding in tansy oil poisoning; the consumer reference adds kidney or liver damage. No LiverTox record for tansy was found, so there is no formal liver-injury rating, and no case series with lab values was read. Authoritative guidance ^{9 21}
• Daisy-family skin allergy. Tansy is in the daisy family (Asteraceae). In a Danish patch-test series of 190 people already allergic to daisy-family plants, tansy was among the plants that most often caused a positive skin test (after feverfew). A review lists tansy among recognised sensitising plants. People allergic to ragweed, chrysanthemum, chamomile or feverfew may react. Case series ^{17 10 21}
• Do not confuse with tansy ragwort. Tansy ragwort (Jacobaea vulgaris, also called Senecio jacobaea) is a different plant. Its pyrrolizidine alkaloids damage the liver and are a known problem for livestock and people. Nothing we read says common tansy (Tanacetum vulgare) contains these alkaloids, so the two are kept apart on this page. 'Blue tansy' oil comes from another species too and is not covered here. Authoritative guidance ^{19 23 5 6}

No LiverTox entry for tansy was found, so there is no standard rating of liver-injury likelihood. The JECFA monograph lists hepatitis among signs of tansy oil poisoning and a consumer reference lists liver damage. We read no case with blood-test values. Tansy ragwort, a different plant, does cause pyrrolizidine alkaloid liver injury; that must not be applied to common tansy. ^{9 21 23}

How often. No frequency was found. Not finding reports is not proof of safety.

Monitoring. No agency monitoring advice was found. Anyone with liver disease should avoid it.

This is a safety connection. It is not evidence that Tansy supports liver health.

Summary. The main hazard is thujone (a nerve toxin) and, in camphor-type plants, camphor. Content differs hugely between plants, so risk differs too.

Animal. JECFA: tansy oil acute oral LD50 in rats 1.15 g/kg, dermal LD50 in rabbits above 5 g/kg; toxic to dogs by mouth at 300 mg/kg. A Bulgarian camphor-type oil (6% thujone) was non-toxic by mouth in a single-dose rat test; its intraperitoneal LD50 was 14.9 g/kg. Thujone itself causes convulsions in rodents, rabbits and cats; long studies show nerve toxicity as the main outcome and equivocal cancer signals in rats.

Human doses studied. None. No human dosing study of tansy exists, and a consumer reference says there is not enough science to give a dose.

High dose or long term signals. Human poisoning with convulsions and death has been reported for oil, and deaths are reported after teas and powders (consumer reference, details not verified).

Overdose response. Seek emergency care. Camphor has a separate US poison-centre guideline (hospital referral threshold for ingestion; effects not described in the abstract read).

Genotoxicity. Not assessed for tansy in the sources read. For thujone the toxicology review reports equivocal evidence of carcinogenicity in rats.

Toxic plant parts. The oil from leaves and flowering tops is the most concentrated source. The whole herb (tea, powder) has also been linked to deaths in a consumer reference.

No contamination study of tansy products was found. The big quality issue is that the toxic content varies by plant type.

Chemotype changes the thujone and camphor content. In 40 Norwegian wild populations, seven oil types were found: beta-thujone (22 plants), camphor (6), alpha-thujone (2) and others. A Bulgarian oil had 6% thujone and 25% camphor; JECFA gives about 50% thujones for tansy oil. A label rarely states the type. ^{20 11 9}

Look-alike and name confusion. Tansy ragwort (Jacobaea vulgaris) is a separate, liver-toxic plant; 'blue tansy' oil is another species. Check the Latin name. ^{21 5 19}

• Seizure, convulsions, confusion or loss of consciousness after swallowing tansy or its oil: call emergency services or poison control at once.
• Repeated vomiting, severe diarrhoea or belly pain, vomiting blood or black stools.
• Yellow skin or eyes, dark urine, much less urine than usual.
• Pregnant and swallowed tansy in any form: seek urgent medical care.
• A child swallowed any tansy product: call poison control now.

Stop the supplement and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.