PawAI LabPawAI LabTry it Free

Tansy Poisoning in Dogs: Mechanism, Signs, and Prognosis

PawAI Lab
7 min read

Learn how thujone in tansy affects dogs, what clinical signs may develop, how a veterinarian may approach treatment, and what prognosis to expect after exposure.

Quick Answer

Tansy (Tanacetum vulgare) is toxic to dogs because it contains thujone and other essential oils. Thujone acts on the central nervous system and can also damage the liver. Acute exposure may cause gastrointestinal upset, drooling, and depression, with more serious cases progressing to incoordination, tremors, or seizures. All parts of the plant may pose a risk. If your dog ate tansy, contact a veterinarian or an animal poison-control service right away, even if your dog appears well at this time.

Before using any tool, contact a veterinary professional if your dog may have eaten tansy.

  • US: ASPCA Animal Poison Control (888-426-4435) or Pet Poison Helpline (855-764-7661)
  • UK: Animal PoisonLine (01202 509000) or your nearest veterinary emergency clinic
  • Canada: ASPCA Animal Poison Control (888-426-4435) or Pet Poison Helpline (855-764-7661)
  • AU: Animal Emergency Centre or your regular vet
  • EU: Contact your nearest veterinary emergency service

TOXICITY CHECKER

Check the item and pet details for general, species-aware risk information while you contact a veterinary professional when needed.

Check an Item

Do not delay emergency veterinary or poison-control advice to use this tool.

Safety Verdict

Toxic. Tansy (Tanacetum vulgare) contains thujone, a monoterpene ketone, along with other essential oils. Thujone is the principal toxic compound. It affects the central nervous system by reducing the activity of GABA, an inhibitory neurotransmitter that normally helps keep nerve signaling calm and controlled. When GABA activity is reduced, the nervous system can become overexcited, which may lead to tremors and seizures.

In addition to its effects on the nervous system, thujone and the essential oils in tansy can be toxic to the liver. Liver damage may develop alongside or after the neurological signs. All parts of the plant may contain these compounds, with the flowers and leaves typically carrying the highest concentrations. The plant grows wild in meadows and along roadsides and is sometimes cultivated in gardens.

What Should the Owner Do Now?

  1. Contact a veterinarian or animal poison-control service immediately. Early assessment can help reduce the risk of nervous system or liver complications.
  2. Do not induce vomiting unless a veterinarian or poison-control professional directly instructs you to do so. With nervous system toxins, inducing vomiting carries additional considerations and should only be decided by a professional.
  3. Collect relevant information (see the section below) so the veterinary team can assess the situation accurately.
  4. Do not give food, milk, salt, charcoal, or any home remedy. These are not proven treatments and may interfere with veterinary care.
  5. Follow the veterinarian's instructions regarding whether to bring your dog in for examination, decontamination, monitoring, or supportive care.

Even if your dog ate only a small amount and seems fine, professional consultation is still warranted because neurological and liver signs may not appear for several hours.

What Signs May Occur?

Signs of tansy poisoning in dogs may develop within a few hours of ingestion. Not all signs will appear in every dog, and the severity can depend on the amount eaten.

Gastrointestinal signs may appear first:

  • Vomiting
  • Diarrhea
  • Drooling or excessive salivation
  • Reduced appetite

Because thujone affects the central nervous system, additional signs may develop:

  • Depression or lethargy
  • Ataxia (unsteady walking or loss of coordination)
  • Tremors or muscle twitching
  • Seizures in severe cases

Liver effects may develop over a longer timeframe and can include:

  • Yellowing of the gums, skin, or whites of the eyes (jaundice)
  • Increased thirst or changes in urination
  • Continued weakness or lethargy

Because tansy can affect both the nervous system and the liver, veterinary monitoring may be recommended even when a dog initially appears stable. Absence of early signs does not necessarily rule out risk.

What Information Should Be Ready?

When you contact a veterinarian or poison-control service, having the following details available can help them assess the situation more efficiently:

  • Dog's details: species, breed, approximate age, and body weight
  • Plant involved: tansy (Tanacetum vulgare), and whether the dog chewed leaves, stems, or flowers
  • Estimated amount: best guess of how much plant material was swallowed
  • Time of ingestion: when the exposure occurred, or the window of time during which it may have happened
  • Current symptoms: any vomiting, diarrhea, drooling, lethargy, ataxia, tremors, or seizures
  • Plant sample: if available, a photo or a piece of the plant to confirm identification
  • Medical history: any pre-existing liver disease, neurological conditions, or current medications

Provide honest estimates rather than precise measurements. The veterinary team can work with approximate information to determine the best course of action.

Differences That May Affect Risk

Several factors can influence how tansy affects an individual dog:

  • Part of the plant: The flowers and leaves typically contain the highest concentrations of thujone and essential oils. Stems may contain lower amounts but are still unsafe.
  • Body size: Smaller dogs may be at greater risk from a given amount of plant material, though toxicity is possible in dogs of any size.
  • Existing liver conditions: Dogs with pre-existing liver disease may be more vulnerable to additional liver damage from thujone.
  • Individual variation: Reactions can differ between dogs, and the amount ingested is not always easy to determine.

Because of these uncertainties, any known or suspected ingestion should be treated as potentially serious.

When to Contact a Veterinarian

Contact a veterinarian or animal poison-control service immediately if your dog has chewed or swallowed any part of a tansy plant. Do not wait for symptoms to appear.

Emergency signs that require urgent veterinary attention include:

  • Persistent vomiting or diarrhea
  • Unsteady walking or loss of coordination
  • Tremors or seizures
  • Weakness or collapse
  • Yellowing of the gums or whites of the eyes
  • Any change in your dog's responsiveness

Non-urgent follow-up: If the ingestion occurred hours or days ago and your dog appears normal, a veterinary examination is still recommended to check for delayed nervous system or liver effects. Blood tests to assess liver function may be advised.

FAQ

How does thujone affect dogs?

Thujone, the main toxic compound in tansy, reduces the activity of GABA, an inhibitory neurotransmitter in the brain. This can lead to overexcitation of the nervous system, which may cause tremors or seizures. Thujone may also damage the liver. A veterinarian can assess the relevance to an individual case.

What is the prognosis for tansy poisoning in dogs?

The prognosis is generally favorable when a dog receives prompt veterinary care before serious signs develop. Outcomes can be more guarded when seizures have occurred or when significant liver damage is present. Early contact with a veterinarian improves the likelihood of a good outcome.

How is tansy poisoning in dogs treated?

Treatment may include decontamination under veterinary direction, activated charcoal to reduce absorption, intravenous fluids, and supportive monitoring of the nervous system and liver. If seizures occur, a veterinarian may manage them with appropriate medication. Liver-protective support and follow-up blood work may also be part of the care plan.

TOXICITY CHECKER

Not sure whether another plant or household item may be risky for your dog? Get general, species-aware safety information in seconds.

Open Toxicity Checker

This tool provides general safety information only and does not replace veterinary advice.

Sources

Disclaimer

This article and the PawAI Toxicity Checker provide general safety information and cannot determine an individual pet's toxicity risk or replace a veterinarian or animal poison-control service. If exposure may have occurred, contact an appropriate professional promptly, even if your pet appears well.

Written by PawAI Lab