Holly is toxic to dogs. The toxic principle is saponins which can cause gastrointestinal disturbances (vomiting, diarrhea) when ingested.
What is holly?
|Botanical name||Ilex spp.|
|Common names||English holly, European holly, Christmas holly, Holly, Holm, Hulst, Hulver|
|Mature height||1.5 to 24 metres (5 to 80 feet)|
|Native to||Europe, North Africa and western Asia|
|Toxicity||Toxic to dogs|
|Toxic compounds||Saponin glycosides, methylxanthines, and cyanogens|
|Toxic parts||All parts (the highest concentration in young leaves and berries)|
|Severity||Mild to moderate|
What is holly?
Holly is a genus of over 400 species¹ of evergreen and deciduous trees, shrubs, and climbers native to Europe, North Africa and Western Asia. The shiny, stiff leaves are ovate or oblong with wavy, spiked or smooth margins. White flowers are produced in late spring to early summer, followed by attractive red fruit (commonly referred to as berries) in winter.
Holly is used to decorate homes during the Christmas period. Its association with Christianity is due to the spiny leaves symbolising the ‘crown of thorns’ placed on the head of Jesus Christ and the red fruit which symbolises his blood that was shed for humanity². However, the use of holly predates Christianity. Druids, Celts and Romans believed that evergreen holly warded off evil spirits³ and the ancient Romans gave each other holly during Saturnalia as a symbol of friendship⁴.
Related: Caring for a Christmas tree
Holly contains saponins, methylxanthines, and cyanogens within the leaves and fruit. 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 derive their name due to unique foaming characteristics in aqua solutions⁵. Ingestion of saponins causes gastrointestinal irritation and when administered intravenously saponins have been shown to be hemolytic (causing the red blood cells to rupture). Methylxanthines and cyanogens do not appear to be a significant risk to dogs⁶.
In addition to the toxic properties listed above, many common species of holly including English (Ilex aquifolium) and American (Ilex opaca) have short, sharp points known as acute apices⁷ along the leaf margin. When chewed, acute apices cause mechanical damage to the delicate tissues of the mouth. This should be enough to deter most dogs from consuming holly leaves, however, the red fruit may be attractive to some dogs, especially puppies.
There is no data on the toxic dose of holly berries in dogs, however, as little as five holly berries can cause vomiting in children⁸.
What are the symptoms of holly poisoning in dogs?
Saponins are poorly absorbed by the gastrointestinal tract, as well as mechanical injury from the prickly spines on the leaves of some holly species.
- Oral bleeding
- Pawing at the mouth
- Vomiting (possibly with blood)
- Loss of appetite
- Abdominal pain (sensitivity when touched, tucked-up appearance)
If it is safe to do so, remove any remaining plant matter from the dog’s mouth and offer a drink of water or milk. Contact your veterinarian or an emergency pet poison helpline for advice. If the dog appears well, the veterinarian may recommend a wait-and-see approach. However, if the dog is displaying clinical signs, treatment may be necessary.
There is no antidote to holly toxicity and treatment is aimed at managing clinical signs. If ingestion was recent, the veterinarian may induce emesis to decontaminate the gastrointestinal tract of holly. This will be followed by the administration of activated charcoal to bind to any remaining plant matter and prevent further absorption. Intravenous fluids will be given to treat or prevent dehydration and electrolyte derangements caused by vomiting along with antiemetics to control vomiting.
A bland diet may be recommended to rest the gastrointestinal tract while the dog recovers.
The prognosis for dogs who have ingested holly is favourable and most dogs will make a full recovery within 2 – 5 days.
- HOLLY (Ilex) Genus Overview. (n.d.). Retrieved October 15, 2022
- The Symbolism of the Advent Wreath. (n.d.). Retrieved October 15, 2022
- Amazing Species: Holly. (n.d.). Retrieved October 15, 2022
- Peeples, E. A. (1994). Planting an Inheritance. Stackpole Books
- Francis, G., Kerem, Z., Makkar, H. P. S., & Becker, K. (2002). The biological action of saponins in animal systems: a review. British Journal of Nutrition, 88(6), 587–605.
- Ilex – an overview | ScienceDirect Topics. (n.d.). Www.sciencedirect.com. Retrieved October 15, 2022
- Ilex aquifolium. (n.d.). Keyserver.lucidcentral.org. Retrieved October 15, 2022
- Evens, Z. N., & Stellpflug, S. J. (2012). Holiday Plants with Toxic Misconceptions. Western Journal of Emergency Medicine, 13(6), 538–542. Retrieved October 16, 2022