Pennyroyal Oil Poisoning in Dogs

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Pennyroyal Oil from Poisonous Plant for Dogs

Pennyroyal oil is derived from plants within the mint family known as Labiatae. It is frequently used in flea powders and sprays and in fragrances. It can be toxic to dogs, particularly when ingested. There has been one reported case of a dog suffering pennyroyal oil poisoning from dermal (skin) exposure as well.

Symptoms and Types

Symptoms expected with pennyroyal oil poisoning include:

  • Listlessness
  • Vomiting
  • Diarrhea
  • Coughing up blood
  • Difficulty breathing
  • Bloody nose
  • Lethargy
  • Coma
  • Seizures
  • Death


The active poison in pennyroyal oil is a chemical known as pulegone, which is toxic to the liver and can cause severe liver damage.


Physical examination findings consistent with pennyroyal oil poisoning together with a history of exposure to plants, fragrances, or flea products containing pennyroyal oil may prompt suspicion of toxicity.

Blood tests reveal abnormalities consistent with liver damage, including elevated liver enzymes (alanine aminotransferase, alkaline phosphatase, aspartine aminotransferase, gamma-glyamyl transferase) and evidence of bleeding (anemia and prolonged clotting times.)

Evidence of hemorrhage (bleeding) may be seen in internal organs, such as the lungs, liver and kidneys.

A definitive diagnosis may be obtained by finding pulegone on gas chromatography (a specialized laboratory test that analyzes for specific chemicals.)

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