In autumn, parks fill up with shiny conkers under the horse chestnut trees, and paths with acorns. For many dogs, it is a toy that falls from the sky. But are chestnuts toxic to dogs? In short: horse chestnuts are, and so are acorns. Here is what the risk involves, which signs to watch for and how to walk your dog without worry during the season.
Are chestnuts toxic to dogs? Horse chestnut versus sweet chestnut
The horse chestnut is the ornamental tree found in many parks and avenues. Its fruit, the conker, contains saponins, mainly aescin, and the glycoside aesculin. These substances are not only in the seed: they are also in the spiky green husk and in the leaves.
The sweet chestnut, the kind sold roasted at street stalls, is not considered toxic to dogs. Raw, however, it is hard to digest, and its husk with fine spines can injure the mouth and paws. This is how to tell them apart:
- Horse chestnut: green husk with a few short, thick spikes; rounded, glossy brown fruit with a pale patch.
- Sweet chestnut: husk covered in long, fine spines; flatter fruit that ends in a point.
Even so, on walks one simple rule is enough: chestnuts on the ground stay on the ground.
Why horse chestnuts are dangerous for dogs
- Irritant substances: saponins irritate the lining of the stomach and intestine. The usual result is vomiting, diarrhoea, abdominal pain and restlessness. How severe it is depends on the size of the dog and the amount swallowed.
- Foreign body: a whole conker is hard and just the right size to be swallowed and get stuck in the intestine. An intestinal blockage is an emergency that often requires surgery. Small and medium-sized dogs are at greater risk.
Playing with them is not harmless either: when a dog chews them, it swallows pieces and substances, and a thrown conker can go straight down the throat when the dog catches it.
Acorns, walnuts and fallen fruit: other autumn hazards
- Acorns: they contain a lot of tannins, which irritate the digestive system; in larger amounts they can also affect the kidneys. And, like conkers, they can cause a blockage.
- Walnuts on the ground: those that fall from the tree soon go mouldy, and some of the toxins in those moulds can cause tremors and seizures in dogs. Mouldy walnuts: hands off.
- Fallen fruit: fermented fruit under the trees upsets the stomach and attracts wasps.
My dog ate a chestnut: what to do
- Stay calm and remove any pieces left in their mouth, if you can do so safely.
- Call your vet or an emergency vet straight away, without waiting for symptoms to appear. Tell them your dog's weight and age, when it happened and roughly how much they ate.
- Do not make them vomit yourself or give home remedies such as salt water. The cure can be worse than the disease.
- Take a sample, for example a conker or acorn from the same tree, to make it easier to assess the case.
- Keep a close eye on them: vomiting, diarrhoea, retching, loss of appetite, a hard or painful abdomen and lethargy are warning signs, even hours later.
How to enjoy worry-free walks in chestnut season
- Adapt your route: under chestnut and oak trees, keep your dog on a short lead, or avoid those paths during the weeks when the fruit falls.
- Practise ‘drop it’ and swapping: a reliable command to let go is worth its weight in gold in autumn. Train it at home with a toy and swap it for a treat so that letting go pays off.
- Don't throw conkers for them: a ball or a fetch toy too big to swallow is a better choice.
- Put away decorations and crafts: bowls of conkers or acorns and autumn crafts from school should be kept out of reach.
- Give their nose a job at home: many dogs love foraging for food in the street. Sniffing games at home channel that curiosity safely. Mealtimes can become a small challenge too: in our silicone slow feeder with 5 zones, the kibble is spread out and your dog has to get it out bit by bit.
In short
Horse chestnuts and acorns are toxic to dogs and can also block the intestine. The sweet chestnut is not considered toxic, but raw and in its husk it shouldn't end up in your dog's mouth either. With a short lead under the trees, a good ‘drop it’ and suitable toys, you can enjoy autumn in peace. And if your dog has swallowed something, better to call the vet one time too many than one time too few.
This article is for information only and is not a substitute for veterinary advice.