Tansy, particularly the species Tanacetum vulgare (common tansy), has a long history of use in folk medicine and as an ornamental plant. However, modern scientific understanding confirms its potent toxicity, with serious and potentially fatal side effects from ingestion. The primary danger lies in its toxic chemical compounds, which can cause significant damage to multiple bodily systems. It is not considered safe for internal consumption or application to broken skin.
The Primary Toxin: Thujone
The most dangerous component of common tansy is thujone, a potent neurotoxin found in the plant's volatile oil. Thujone acts as a GABA receptor antagonist, which means it interferes with a major neurotransmitter in the brain that helps regulate neuronal excitability. This interference can lead to severe neurological symptoms. Small doses of tansy oil, as little as 10 drops, have been reported to be fatal.
Symptoms of thujone poisoning include:
- Restlessness and tremors
- Dizziness
- Convulsions and seizures
- Hallucinations and psychosis in large doses
- Brain damage
The toxic effects are dose-dependent, but any internal use is extremely risky. It is important to note that the concentration of thujone can vary depending on the plant and time of year, making a 'safe' dose impossible to determine.
Systemic and Organ Damage
Beyond the neurological effects, tansy poisoning can cause widespread damage to other organ systems. The poisonous properties of the plant, primarily from thujone and other alkaloids, can accumulate in the body over time, leading to long-term health complications.
Liver and Kidney Failure
Ingestion of tansy can cause significant and sometimes irreversible liver and kidney damage. This damage can manifest as a buildup of toxic metabolites, leading to conditions like liver cirrhosis or failure. Symptoms of liver damage can include a pig-like odor in cattle (indicating severe hepatic issues), fluid buildup in the abdomen (ascites), and a yellowish discoloration of mucous membranes.
Gastrointestinal Distress
Tansy can cause severe gastrointestinal issues, including vomiting, severe diarrhea, stomach pain, and inflammation. The toxic properties can irritate the lining of the digestive tract and disrupt normal function. Ingesting tansy ragwort, in particular, can lead to bloody diarrhea.
Increased Bleeding
Bleeding problems have been reported in cases of tansy poisoning. This can be a complication of liver damage, as the liver plays a critical role in producing clotting factors. Any unexplained bleeding, such as bleeding from the gums or bloody stool, should be considered a medical emergency.
Allergic and Skin Reactions
Even external contact with tansy can be dangerous. The plant's volatile oil, containing thujone, can cause skin irritation or contact dermatitis in sensitive individuals. Handling the plant without gloves is not recommended.
Symptoms of skin contact include:
- Redness and rash
- Itching and swelling
- Severe skin reactions
Furthermore, people with allergies to other plants in the Asteraceae (or Compositae) family, which includes ragweed, chrysanthemums, and marigolds, may experience an allergic reaction to tansy.
Risks for Specific Populations
Certain individuals are at an even higher risk of harm from tansy exposure.
Pregnancy and Breastfeeding
Tansy is considered extremely unsafe for pregnant women. It is known to cause uterine contractions and can induce an abortion. The poisonous thujone can also be passed to an infant through breast milk, making it unsafe for breastfeeding mothers.
Children
Children are particularly vulnerable to the toxic effects of tansy due to their smaller body size and developing organs. Consumption of any part of the plant should be considered a medical emergency for a child.
Individuals with Underlying Conditions
People with liver disease or porphyria, an inherited metabolic condition, should strictly avoid tansy. The toxic alkaloids and thujone can worsen pre-existing liver conditions, and there is concern that tansy might exacerbate porphyria.
Common Tansy vs. Tansy Ragwort: A Comparison
It is important to differentiate between common tansy and tansy ragwort, as both are highly toxic but contain different primary compounds. Misidentification can lead to confusion, but both should be avoided for internal consumption.
| Feature | Common Tansy (Tanacetum vulgare) | Tansy Ragwort (Senecio jacobaea) |
|---|---|---|
| Appearance | Yellow, button-like flowers in clusters with no petals. | Daisy-like flowers with distinct ray petals. |
| Primary Toxin | Thujone. | Hepatotoxic pyrrolizidine alkaloids (PAs). |
| Symptoms | Convulsions, seizures, vomiting, diarrhea, liver damage. | Liver failure, bloody diarrhea, weight loss, neurologic issues. |
| Ingestion Risk | Highly toxic; as little as 10 drops of oil can be lethal. | Highly toxic, especially when dried in hay, leading to irreversible liver damage. |
| Action in Body | Acts on the nervous system and multiple organs. | Causes gradual, irreversible liver cell damage. |
Serious Symptoms of Tansy Poisoning
If you or someone else has ingested tansy, it is critical to seek immediate medical attention. The symptoms can be severe and life-threatening. The following signs indicate a medical emergency:
- Vomiting and severe diarrhea: Can lead to dehydration and electrolyte imbalance.
- Stomach pain: Intense abdominal cramps and pain.
- Dizziness and loss of coordination: Indicates neurological effects.
- Tremors and seizures: A direct result of thujone's neurotoxic properties.
- Liver or kidney damage: Visible signs can include jaundice (yellowing skin), dark urine, and fluid retention.
- Rapid, weak pulse: A sign of systemic distress.
- Bleeding: Unexplained bleeding.
If poisoning is suspected, call a poison control center immediately.
Conclusion
The side effects of tansy, both common tansy and tansy ragwort, are severe and life-threatening, ranging from gastrointestinal distress and contact dermatitis to permanent liver and kidney damage, seizures, and death. The toxic compounds, including thujone and pyrrolizidine alkaloids, make this plant exceptionally dangerous for internal consumption by both humans and livestock. Given the extreme risks, tansy should never be used for self-medication, especially by pregnant women, children, and those with pre-existing health conditions. The historical use of this herb does not negate its modern-day toxicological evidence. Always err on the side of caution and treat tansy as a poisonous plant. For more detailed information on tansy and its potential risks, consult reliable medical sources such as WebMD.
Specific Contraindications and Interactions
Due to its high toxicity, tansy should be avoided in several specific situations and in combination with certain substances.
Pregnancy and Lactation: As previously mentioned, tansy can induce uterine contractions and cause abortion, and its toxic compounds can be passed through breast milk. Children under 7: Children are more susceptible to toxic effects due to their smaller body mass and developing systems. Cholelithiasis (Gallstones): The herb can stimulate bile flow, potentially causing stones to move and leading to biliary colic. Allergies: Individuals allergic to plants in the Asteraceae/Compositae family should avoid tansy. Alcohol: Tansy can increase the drowsiness caused by alcohol, and combining them is not recommended. CYP450 Enzyme Inducers: Tansy ragwort is broken down by the liver, and medications that increase liver enzymes (like CYP3A4 inducers) could potentially increase the toxic effects.
This information emphasizes that tansy is not a safe herbal remedy and should be handled with extreme care or avoided altogether. The severe consequences far outweigh any unsubstantiated traditional uses.
