Is Lily of the Valley Toxic to Dogs?

Lily of the valley (Convallaria majalis) is highly toxic to dogs, the toxic principles are cardiac glycosides, (primarily convallarin and convallamarin) and saponins. Cardiac glycosides plant steroids that affect the heart, and saponins are steroid or triterpene glycosides that cause gastrointestinal upset. All parts of lily of the valley including the leaves, flowers, berries, stems and bulbs are toxic.

What is lily of the valley?

Family Asparagaceae
Botanical name Convallaria majalis
Common names Lily of the valley, European lily of the valley, Our lady’s tears, May bells, Mary’s tears
Leaf colour Green
Flower colour White and pink
Toxicity Toxic to dogs
Toxic properties Cardiac glycosides and saponins
Toxic parts All parts (highest concentrations are in the roots)

Lily of the valley is a flowering bulb native to Eurasia which produces small, fragrant, bell-shaped, white flowers in early spring.  The plant grows to a height of 15 cm, with strappy, green leaves.  Lily of the valley is typically grown outdoors, and occasionally used in bridal bouquets, but are rarely used as a cut flower in homes.

The preferred habitat for lily of the valley is woodlands with rich soil, and is a popular ground cover plant in gardens. The sweet-smelling flowers bloom from early spring, symbolising the end of winter.

Lily of the valley contains at least 38 cardiac glycosides. Direct ingestion of lily of the valley is uncommon in dogs but may occur if the dog consumes grass clippings containing lily of the valley or lily of the valley medications.

Toxicity

Saponins are bitter-tasting, amphiphilic glycosides of steroids and triterpenes widely distributed in the plant kingdom. These phytochemicals protect the plant against bacteria, fungi, parasites, insects and herbivores. Saponins consist of hydrophobic polycyclic triterpenes or steroidal sapogenin and one or two hydrophilic glycoside moieties attached to the backbone. Ingestion of plants containing saponins can cause gastrointestinal upset including nausea, vomiting, diarrhea and loss of appetite.

Cardiac glycosides are a group of chemical compounds where a sugar molecule is bound to a non-carbohydrate molecule. Convallarin and convallamarin inhibit the enzyme Na+/K+-ATPase pump. This ion pump is embedded in the cellular membrane and uses the molecule adenosine triphosphate (ATP) as a source of energy. For every ATP used, three sodium ions are exported and two potassium ions are imported. Cardiac glycosides inhibit the activity of the ATPase pump, which causes an increase in sodium and calcium within the cells, increasing myocardial contractility (the force with which the heart contracts) as well as vagal contractility, which slows down the heart.

Na+/K+-ATPase pump
Chart of membrane transport shows that active transport of ions across the cell membrane is performed by ATPase pumps or transporter proteins.

 

All parts of lily of the valley are toxic to dogs including the leaves, stems, flowers, berries and bulbs.

Clinical signs

Symptoms of lily of the valley poisoning can present as gastrointestinal or cardiac dysfunction. Common signs include the following:

Gastrointestinal

  • Anorexia
  • Nausea
  • Drooling
  • Vomiting
  • Diarrhea
  • Abdominal pain

Cardiac

  • Arrhythmia (irregular heartbeat)
  • Bradycardia (slow heartbeat)
  • Collapse
  • Death

Other

  • Seizures
  • Blurry vision
  • Skin rash
  • Hypotension
  • Neurological disorders

What to do if your dog ingests lily of the valley

Lily of the valley is extremely toxic to dogs and it is critical you seek urgent veterinary care. Contact your nearest veterinarian or pet poison helpline and let them know when the dog consumed lily of the valley and how much. Do not induce vomiting unless the veterinarian recommends you do so.

How much lily of the valley is toxic to dogs?

A lethal dose hasn’t been established in dogs, and due to the huge size difference, it would be difficult to establish. In mice, a lethal dose that kills 50% of the population (LD50)  has been reported to be of 2 grams > kg.

Treatment

Unfortunately, there is no antidote to lily of the valley poisoning. The goal of treatment is to prevent any further absorption of the toxins by gastric decontamination such as gastric lavage (pumping the stomach), or inducing vomiting. After decontamination,  administration of activated charcoal to bind to any remaining plant matter in the gastrointestinal tract.

Managing cardiac symptoms which may include lidocaine or atropine to manage abnormal heart rhythms as well as oxygen therapy if needed.

Intravenous fluids will be administered to treat or prevent dehydration and correct electrolyte derangements.

The veterinarian will run repeat blood tests to measure serum potassium levels as well as an electrocardiogram to monitor heart activity.

Is the lily of the valley related to the Lilium species?

Stargazer lily

Lily of the valley is a different species to the Lilium family. Lilium is a family of approximately 90 flowering bulbs grown for their large, trumpet-shaped flowers. Lillium species can grow to a height of 90 – 120 cm, which is considerably taller than lily of the valley. Common varieties of Lilium include the Easter lily, Oriental lily, Day lily, Stargazer lily, Tiger lily and Day lily. While beautiful, members of the Lilium can cause acute kidney injury in cats and dogs and therefore should not ge kept in houses with pets.