Tansy toxicity: how to spot it and what to do

Tansy (Tanacetum vulgare) is a bright, bitter herb sometimes used in folk medicine or as an insect repellent. Trouble starts when people use the wrong part or too much. The plant and especially its essential oil contain thujone and related compounds that can harm the nervous system and other organs. Small, careful topical uses may be low risk for adults, but any internal use, teas, or essential oils can cause serious problems.

What causes tansy toxicity and who’s at risk?

The main culprit is thujone, a natural chemical that can trigger nervous system reactions. Essential oils and concentrated extracts have the highest levels. Young children, pregnant people, older adults, and anyone with epilepsy or a seizure history are at higher risk. Pregnant women should avoid tansy entirely — it can cause uterine contractions and may lead to miscarriage. Pets are also sensitive; keep tansy away from dogs and cats.

Common ways people get poisoned: drinking homemade tansy tea, swallowing tinctures, using concentrated essential oil internally, or accidental ingestion by children or pets. Even rubbing a strong oil on the skin can cause problems if it’s not diluted properly.

Common symptoms to watch for

Symptoms usually show within hours. Early signs include nausea, vomiting, stomach cramps, and diarrhea. As toxicity grows, expect dizziness, headache, confusion, tremors, and muscle twitching. Severe poisoning can cause seizures, rapid breathing, fast or irregular heartbeat, and loss of consciousness. If you see hallucinations or a sudden seizure after tansy exposure, act fast.

If you suspect tansy poisoning, don’t wait. Call your local poison control center or emergency services right away. If the person is awake and alert and the exposure was recent, the poison control specialist may recommend giving activated charcoal — but only under professional advice. Do not induce vomiting unless told to do so by a medical professional.

Emergency care focuses on supporting breathing and circulation, controlling seizures (often with benzodiazepines), replacing fluids, and monitoring heart function. Take the plant sample, the bottle label, or a photo to the hospital — that helps staff identify the exact exposure and choose the right treatment.

Want to use tansy safely? Don’t take it internally. Avoid essential oils unless handled by an experienced herbalist or aromatherapist, and never give them to children, pregnant people, or pets. If you’re using tinctures or teas found online, check for clear dosing info and certifications. Better yet, choose safer, well-studied herbs for digestive or insect-repellent uses.

Bottom line: tansy can be useful around the garden, but it’s risky inside the body. If someone shows worrying symptoms after contact or ingestion, get medical help quickly and bring the product or plant sample with you.