By Dial A Vet Veterinary Team
Cats rarely eat chestnuts on purpose. When they do, it is usually a kitten batting a conker brought inside by the kids, or a cat investigating a plate of roasted chestnuts left on the coffee table. A small nibble of plain cooked sweet chestnut is unlikely to cause harm. Horse chestnuts are a different story, because the seeds and plant parts are toxic to cats as well as dogs. For a cat, neither belongs on the menu.
Key takeaways
- Sweet chestnuts (Castanea) are not toxic, but they are starchy, hard to digest and of no nutritional value to cats.
- Horse chestnuts (Aesculus), often called conkers, are toxic to cats and can cause vomiting, diarrhoea and other signs.
- Chestnuts and conkers can cause choking or a gut obstruction in a small cat.
- Chestnut dishes may contain butter, onion, garlic, alcohol or sugar, which are not safe for cats.
- If you are not sure which type your cat ate, call your vet.
- Related: toxic and safe plants for pets, signs of poisoning in cats.
Cats are not built for chestnuts
Cats are obligate carnivores. Their bodies are tuned to use protein and fat from animal tissue, and they have a limited ability to handle large amounts of starch. Sweet chestnuts are mostly carbohydrate. Even cooked and peeled, they offer a cat nothing it needs, and a cat that eats a chunk may end up with vomiting, soft stools or wind.
Sweet chestnut or horse chestnut?
Sweet chestnuts come in a case covered in long, fine spines and usually have two or three flattened nuts with a pointed tip. Horse chestnuts have a thicker case with short, blunt spikes (or none) and usually a single round, glossy seed. Horse chestnut leaves look like an open hand with five to seven leaflets.
Horse chestnut trees are grown as ornamental trees in some cooler parts of Australia. Children often collect conkers, so they can end up on bedroom floors and in school bags where cats find them.
Why conkers are a concern for cats
Horse chestnut seeds, leaves, bark and flowers contain saponins such as aesculin. In cats, eating conkers or chewing the plant can cause drooling, vomiting, diarrhoea and abdominal pain. Larger exposures may lead to wobbliness, dilated pupils, depression or agitation. A whole conker is also large relative to a cat's gut and could cause an obstruction.
The other chestnut risks
- Choking. Pieces of nut or shell can lodge in a cat's throat.
- Spiny burrs. Sweet chestnut spines can get stuck in paws, lips or gums.
- Chestnut dishes. Stuffing, soups and Christmas recipes often include onion, garlic, butter, cream and sometimes brandy. Onion and garlic can damage a cat's red blood cells, and alcohol is dangerous in small amounts.
- Candied chestnuts (marrons glacés). Very sugary, sticky and unsuitable.
Signs to watch for
- Drooling, gagging or pawing at the mouth
- Vomiting or diarrhoea
- Loss of appetite, hiding or lethargy
- A hunched posture or tender belly
- Wobbliness, dilated pupils or unusual behaviour
- Pale gums, weakness or fast breathing a few days after eating onion or garlic
When it is an emergency
Take your cat to a vet immediately if they are choking or struggling to breathe, or if they have eaten or chewed horse chestnut seeds or plant parts. Also seek urgent care for repeated vomiting, refusal to eat for more than a day, a painful belly, collapse or tremors, or if your cat ate a chestnut dish containing onion, garlic or alcohol. Call your vet or the Animal Poisons Helpline (1300 869 738) if you are unsure. Never try to make a cat vomit at home.
How vets diagnose and treat it
Bring a photo or sample of the nut, leaf or dish if you can. Your vet will examine your cat, including the mouth and belly, and may use X-rays or ultrasound to look for a foreign body. Depending on the exposure and timing, they may consider decontamination, fluids, medicines to settle nausea and protect the gut, and close monitoring. If an obstruction is found, endoscopy or surgery may be needed. Treatment is tailored to your cat.
Prevention
- Keep conkers out of the house, or stored in a closed container if children collect them.
- Do not leave roasted chestnuts or festive dishes unattended.
- Offer cats safe play items such as large toy balls and wand toys.
- Sweep up shells and burrs after cooking or gardening.
Treats cats actually enjoy
- Plain cooked chicken or white fish, without bones or seasoning
- Freeze-dried meat or fish treats made for cats
- A small amount of your cat's usual wet food on a lick mat
- Cat grass to chew safely
FAQ
My cat licked a roasted chestnut. Should I worry?
A lick of plain roasted chestnut is very unlikely to cause harm. Watch for stomach upset and check it was not seasoned.
Are conkers poisonous to cats?
Yes, horse chestnuts are listed as toxic to cats. Call your vet if your cat chewed or swallowed one.
Can cats eat chestnut flour treats?
There is no benefit. If it is in a commercial cat treat, follow the label. Avoid human baking.
Is water chestnut safe for cats?
Plain water chestnut is not toxic, but stir fries often contain onion and garlic. Best avoided.
Talk with a vet
If your cat has been playing with or chewing a nut and you are not sure what it was, a Dial A Vet veterinarian can look at a photo with you and help decide on next steps. Book a Dial A Vet consult.
References
- ASPCA Animal Poison Control Center. Toxic and Non-Toxic Plants: Horse Chestnut (Buckeye, Aesculus spp).
- Cornell Feline Health Center. Feeding Your Cat.
- RSPCA Australia Knowledgebase. What should I feed my cat?
- ASPCA Animal Poison Control Center. People Foods to Avoid Feeding Your Pets.
- Merck Veterinary Manual. Gastrointestinal Obstruction in Small Animals.
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.