Lavender refers to a genus of flowering plants in the mint family, Lamiaceae, known scientifically as Lavandula. This genus encompasses several species and countless cultivars, with English lavender (Lavandula angustifolia) being one of the most common. These plants are characterized by their fragrant purple flower spikes and silvery-green foliage. The very compounds that give lavender its distinctive and pleasant aroma—primarily linalool and linalyl acetate—are also the source of its potential toxicity. These are volatile organic compounds that the plant produces as a natural defense mechanism against herbivores and pests.
From a botanical perspective, the highest concentration of the potentially problematic compounds is found in the plant's essential oils. These oils are stored in tiny glandular trichomes—hair-like structures—on the flowers, leaves, and stems. When a pet brushes against or chews on the plant, these glands can rupture, releasing the concentrated oils. While the fresh plant material contains these oils, they are far more concentrated in products like essential oil diffusers, liquid potpourri, and direct extracts. The two primary terpenes, linalool and linalyl acetate, are metabolized differently by pets than by humans, making them difficult for their livers to process, which leads to the symptoms of toxicity.
Cats are particularly susceptible to lavender toxicity due to their unique physiology. They lack a specific liver enzyme, glucuronyl transferase, which is essential for efficiently breaking down and eliminating certain toxins, including the compounds in lavender. Ingesting even a small amount of the plant, but especially concentrated oil, can lead to poisoning. Symptoms in cats include nausea, vomiting, lethargy, loss of appetite, and in severe cases, neurological signs such as difficulty walking and tremors. Topical exposure to concentrated oil can also cause chemical burns or allergic dermatitis.
Dogs are generally less sensitive to lavender than cats, but it is still considered toxic if ingested in significant quantities. The fresh plant is considered mildly toxic. The larger risk for dogs comes from the ingestion of concentrated essential oils or products containing them. Symptoms of lavender poisoning in dogs are similar to those in cats and can include vomiting, reduced appetite, constipation, and signs of abdominal pain. Ingesting a large amount of plant material can also potentially cause a gastrointestinal obstruction, which is a separate mechanical concern.
The risk of lavender toxicity extends to other small mammals and pets. For herbivores like rabbits, guinea pigs, and horses, the plant's natural defense compounds can be irritating and potentially harmful if consumed in large amounts. Birds have extremely sensitive respiratory systems, and the volatile compounds from lavender plants or, more dangerously, diffused oils can cause significant respiratory distress. For all exotic and small pets, it is prudent to err on the side of caution and avoid planting lavender within their reach or using its essential oils in their environment.
