←
Pennyroyal
Mentha pulegium
Pennyroyal (Mentha pulegium) is a mint family herb that is severely toxic to cats — significantly more dangerous than common mint or peppermint. Its primary toxic compound is pulegone, a monoterpene ketone that is metabolised in the liver to the reactive compound menthofuran. This metabolite causes severe hepatotoxicity and can be lethal, especially in the concentrated essential oil form historically used as a flea repellent.
Important Notes
Toxic compounds: pulegone (primary); metabolised to menthofuran in the liver — the true hepatotoxic agent
Mechanism: menthofuran causes direct hepatocellular necrosis (liver cell death); glutathione depletion amplifies the damage
Symptoms: vomiting, diarrhea, lethargy; severe cases cause acute liver failure with jaundice, tremors, seizures, and collapse
Pennyroyal essential oil is especially dangerous — do NOT use it as a flea treatment; even topical application can cause fatal liver failure
Any exposure to pennyroyal oil is a veterinary emergency; plant ingestion also warrants prompt vet evaluation
Potentially Toxic Parts
Root
Stem
Flower
Possible Symptoms Reported in Cats
Liver damage progressing to liver failure
Hepatic
Seizures, tremors, uncoordinated gait, weakness, and lethargy
Neurological
Vomiting, diarrhea, excessive drooling, loss of appetite, and difficulty swallowing
Gastrointestinal
Difficulty breathing, coughing, and sneezing
Respiratory
Disclaimer: This summary was compiled from multiple sources and is for informational use only. It is not a diagnosis or treatment plan. Toxicity can vary based on the substance, amount, plant part, and individual cat. If you think your cat may have been exposed to a toxic substance, contact a veterinarian right away.