By Dial A Vet Veterinary Team
The word "chestnut" covers two very different trees. Sweet chestnuts (Castanea) are the ones roasted at winter markets and harvested in autumn around places like Bright and Beechworth in north east Victoria. Horse chestnuts (Aesculus), whose shiny brown seeds are known as conkers, are planted as ornamental trees in some cooler parts of Australia and are toxic to dogs. A cooked, peeled sweet chestnut is not dangerous for most dogs. A conker picked up in the park can be.
Key takeaways
- Cooked, peeled sweet chestnuts are not toxic to dogs and are lower in fat than most nuts.
- Horse chestnuts (conkers) contain saponins such as aesculin and can cause severe vomiting, diarrhoea and other signs.
- Whole chestnuts and conkers are a choking and intestinal blockage risk.
- The spiky burrs that surround sweet chestnuts can injure the mouth, paws and gut.
- Candied, glazed or stuffing chestnuts often come with sugar, butter, onion or alcohol.
- Related: intestinal blockage in dogs, autumn hazards for dogs.
How to tell the two apart
Sweet chestnut. The case (burr) is covered in long, fine, needle-like spines. Inside are usually two or three flattened nuts with a pointed tip, often with a small tuft. Leaves are long and single with toothed edges.
Horse chestnut. The case is thick and green with fewer, short, blunt spikes, or none. Inside is usually a single round, glossy brown seed with a pale patch. Leaves are made of five to seven leaflets spreading like fingers.
If you cannot tell which your dog ate, treat it as a horse chestnut and call your vet.
Why horse chestnuts are dangerous
The seeds, leaves, bark and flowers of horse chestnut trees contain saponins, including aesculin. In dogs, eating conkers can cause severe vomiting and diarrhoea, drooling, abdominal pain and, in larger exposures, wobbliness, dilated pupils, depression or excitement, and rarely more serious neurological signs. Conkers are also hard and round, so a large one can block the intestine. Signs often start within a few hours but can be delayed.
Sweet chestnuts: the safer cousin with caveats
Cooked sweet chestnuts are starchy and relatively low in fat compared with nuts such as macadamias or pecans. A small piece of a plain roasted and peeled chestnut is unlikely to harm a healthy dog. Still:
- Whole chestnuts are the right size to lodge in a dog's throat or gut.
- Raw chestnuts are harder to digest and contain tannins that can upset the stomach.
- The shell and inner skin are tough and fibrous.
- Large amounts can cause wind, bloating and diarrhoea.
Chestnut dishes at Christmas or in winter cooking often include butter, sugar, onion, garlic, bacon or brandy. These are the bigger risk.
Burrs and windfalls
Dogs walking under chestnut trees in autumn can tread on or mouth the prickly burrs. Spines can lodge in paws, lips, tongue and gums. Dogs that eat fallen nuts from orchards or parks may also swallow mouldy nuts, which can carry tremorgenic mycotoxins that cause shaking and seizures.
Signs to watch for
- Vomiting, retching or diarrhoea
- Drooling, pawing at the mouth or a sore paw
- A tense or painful belly
- Loss of appetite or lethargy
- Wobbliness, dilated pupils or unusual behaviour
- Tremors or seizures
When it is an emergency
Contact a vet immediately if your dog ate horse chestnuts or you are unsure which type, if they are choking, vomiting repeatedly, have bloody diarrhoea, a painful belly, are wobbly, trembling or having a seizure. Also seek urgent care if your dog cannot keep water down or is straining without passing faeces. The Animal Poisons Helpline (1300 869 738) can advise on Australian exposures. Do not try to make your dog vomit at home.
How vets diagnose and treat it
Your vet will ask about what was eaten, when, and where. A photo of the tree, leaf or nut helps. They will examine your dog and may take X-rays or perform an ultrasound to check for an obstruction. Treatment may include decontamination if appropriate, fluids, medicines to settle nausea and protect the gut, and sometimes removal of a blockage by endoscopy or surgery. Care is tailored to the dog and the exposure.
Prevention
- Learn to identify horse chestnut trees on your regular walks.
- Keep dogs on lead under nut trees in autumn and pick up windfalls in your yard.
- Do not throw conkers for dogs to fetch.
- Keep festive chestnut dishes off low tables.
FAQ
Can dogs eat roasted chestnuts?
A small piece of plain, roasted and peeled sweet chestnut is generally fine. Skip seasoned or buttered versions.
Are water chestnuts the same thing?
No. Water chestnuts are an aquatic vegetable. Plain water chestnut pieces are not toxic, but Asian dishes may contain onion, garlic and salt.
My dog ate a conker but seems fine. Can I wait?
Call your vet now. Signs can be delayed and conkers can cause a blockage.
Is chestnut flour safe for dogs?
Chestnut flour in a dog treat is not a concern. Check homemade baking for other risky ingredients.
Talk with a vet
If your dog has eaten something from under a tree and you are not sure what it was, a Dial A Vet veterinarian can look at photos with you and help decide how urgent it is. Book a Dial A Vet consult.
References
- ASPCA Animal Poison Control Center. Toxic and Non-Toxic Plants: Horse Chestnut (Buckeye, Aesculus spp).
- ASPCA Animal Poison Control Center. People Foods to Avoid Feeding Your Pets.
- RSPCA Australia Knowledgebase. What should I feed my dog?
- Merck Veterinary Manual. Gastrointestinal Obstruction in Small Animals.
- Merck Veterinary Manual. Tremorgenic Neuromycotoxicosis in Dogs.
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. If you are worried about your pet right now, contact your local vet or nearest emergency animal hospital.