Three things fall on Mission sidewalks in October and they carry three different risks. Acorns cause stomach upset and, in quantity, can harm the kidneys. Horse chestnuts, or conkers, are the right size to block a dog’s gut. Sweet chestnuts are the one kind that is not toxic. Knowing which is which is most of the answer.
Telling them apart in thirty seconds
Acorns. Small, oval, pale brown, with a distinctive scaly cap. They drop from oaks in late September and October, in volume, and they roll. Oak leaves fall with them and carry the same compounds, though the brown autumn leaves are much weaker than green spring foliage, so it is the acorns that matter in October.
Horse chestnuts, or conkers. Large, round, glossy mahogany brown with a pale scar on one face, inside a thick green husk with short, widely spaced spikes. The tree has big palmate leaves split into five or seven leaflets from a single point.
Sweet chestnuts. The edible ones. Smaller, flatter on one side, with a pointed tuft at the tip, and the husk is covered in dense, fine, needle-like spines rather than scattered spikes. These are safe in small amounts, though the shells are indigestible.
The husk is the quickest tell. A spiky case like a small green hedgehog holds sweet chestnuts. A smoother case with a few blunt spikes holds a conker.
Acorns: the one that works on the kidneys
Acorns and oak leaves contain tannins, specifically a group called gallotannins. Green and unripe acorns hold more than fully ripe brown ones, which is why early October is worse than November.
The common presentation is a stomach problem. Vomiting, diarrhea that may have blood in it, a dog off their food and clearly uncomfortable in the belly, usually within a few hours to a day. Most dogs who have eaten a few acorns get no further than this.
The less common presentation is the one worth the article. A dog who eats acorns in volume, or who has a daily habit of working the ground under an oak, can develop kidney injury, and liver values can rise as well. That version does not announce itself on the first evening. It shows up as a dog drinking and urinating noticeably more than usual, off their food, flat, and sometimes with a sore mouth. It can be several days after the fact.
So the useful distinction is not how a dog looks tonight. It is quantity and repetition. A dog who has eaten a handful, or who has a daily habit of working the ground under an oak, needs a conversation with us even if nothing has happened yet. A single acorn on a walk is a different matter and usually passes without incident.
There is a second, mechanical problem. Acorns are hard and they come with twigs and caps attached. A small dog who eats a lot of them can end up with a mass of indigestible material that does not move on. Watch for repeated vomiting, no interest in food and a dog going quiet, and phone us if you see it.
Conkers: the one that gets stuck
Horse chestnuts contain aesculin, which causes drooling, vomiting, diarrhea and belly pain, and in a dog that has eaten several it can also cause wobbliness, tremors, weakness or collapse. Those last signs mean the same thing here as they do under a walnut tree: go now. The shape, though, is the more common problem.
The main event is the shape. A conker is round, smooth, hard and roughly the diameter that lodges in the gut of a medium-sized dog. It will not break up or soften the way food does, and in a dog of the wrong size it will not pass. The spiky husk causes pawing at the mouth, gagging and drooling, which is worth a call on its own, and dogs sometimes swallow a conker whole while trying to deal with the case around it.
A blockage looks like this: repeated vomiting, often bringing up nothing but froth or water, no interest in food, a dog who is lethargic and tender over the belly, and nothing much coming out the other end. It builds over a day or two and it gets worse, not better. This often does not resolve on its own. If your dog has swallowed a conker, phone us the same day rather than waiting to see whether it reappears.
Dogs also play with conkers, which is how most of them get swallowed. A conker is almost exactly ball-sized to a Labrador, it bounces unpredictably, and a dog carrying one in their mouth on a walk can inhale it when they bark or run. That version is a choking emergency rather than a blockage.
Walnuts, and the mould that matters
Walnut trees are scattered through older Mission properties and the nuts drop at the same time of year. The nut itself is high in fat, so a dog who eats a pile gets an upset stomach, and a day or two later can develop a painful inflamed pancreas: repeated vomiting, a hunched posture, a dog who will not settle or eat. Phone us rather than waiting that out.
The real concern is what grows on the hulls once they have been lying in wet grass. Walnut hulls left in wet grass grow surface moulds whose by-products act on the nervous system, and they act fast: shaking, twitching, an unsteady walk or a dog who cannot settle, typically inside the first couple of hours. Do not sit with that one. Get in the car.
If your dog has eaten something off the ground
- Check your dog first. Tremors, twitching, wobbliness, repeated retching or distress mean get in the car now and have someone phone as you go.
- Work out what it was. Photograph the husk and a whole example if there is one. The husk is the reliable identifier.
- Estimate how many, honestly. One, a mouthful, or a sustained graze over several days are three different conversations.
- Note where it happened and when. A daily route under the same oak is information we need.
- Do not try to make your dog bring it back up. With something hard and the size of a conker, that can cause an obstruction higher up, which is worse than where it started. Whether it is the right step depends on what was swallowed and when, and that is a judgement to make here.
- Hold off on food until you have spoken to us, because a dog who may need sedation does better on an empty stomach.
- Phone us if we are open, and the nearest open emergency hospital if we are not.
Come in through our urgent care. Our diagnostics team can image the abdomen to see whether something is lodged, and where it is, our surgical services team removes it. The same team runs kidney and liver values where acorns are involved, and with acorn exposure the samples over the following few days are the ones that tell us whether the kidneys have been affected. Our medical services team looks after the days of monitoring in between, and our wellness exams are where a repeated scavenging habit is worth raising before it causes a problem.
Our hours are 8:00 AM to 7:00 PM Monday to Friday and 9:00 AM to 4:00 PM on Saturday and Sunday, and we are closed on statutory holidays. The weekend and the October long weekend are the parts to plan around: we close at four on Saturday and Sunday, and on Thanksgiving Monday we are shut altogether. If your dog swallows a conker at five on a Sunday, or starts tremoring under a walnut tree at any hour we are shut, go straight to the nearest open emergency hospital and have a passenger call ahead rather than holding it overnight.
Keeping it uneventful
- Know your trees on your own route. Two or three oaks and one horse chestnut probably account for most of the risk on the walk you do every day.
- Carry a light you can point once the evenings are dark. You cannot manage what your dog picks up if you cannot see the ground.
- Use a fixed-length leash under the trees rather than an extendable one, so a nose going down is something you feel immediately.
- Interrupt early rather than chase. A dog who learns that a mouthful means being chased will swallow faster next time. Swap for something better and move on.
- Rake up and bag fallen nuts in your own yard weekly through October and November, and get the walnut hulls up before they go mouldy.
- Never let a dog play with a conker. It is the right size to choke on and too often the wrong size to pass.
- Bring your own chew on the walk if your dog scavenges. A mouth that is occupied is not sampling the sidewalk.
Our guide to wet weather paw and skin care covers the other half of the autumn walk, which is what the rain does to feet and coats over a season.
Questions we are asked
My dog ate one acorn. Do I need to do anything?
Probably not beyond keeping an eye on him. A single acorn in a dog of any reasonable size usually causes nothing, or at most a loose stool. What changes the answer is quantity and repetition: a mouthful, or a dog who does this every day under the same tree, is worth a phone call. Also worth a call if he is a small dog, because the same acorn is proportionally a much bigger exposure.
How long does it take for a conker to cause a blockage?
Usually a day or two before it is obvious, which is the problem. The early signs are vague: a bit quiet, less interested in dinner, maybe one vomit that gets written off. Then the vomiting becomes repeated and productive of nothing, and the belly becomes sore. Because the window where this is simplest to deal with is early, we would much rather see a dog on the day the conker went down than on the day the vomiting starts.
Are sweet chestnuts, the ones in the dense needle-covered husk, safe?
Sweet chestnuts are, conkers are not, and the husk is how you tell. A dense needle-covered burr means sweet chestnut, and a dog who eats a couple of roasted ones is fine. The shells are a different matter: they are indigestible and a dog who eats a bowl of them, shells included, can end up with an obstruction. Raw ones also cause more stomach upset than cooked. Harmless is not the same as advisable.
What about oak leaves? My dog chews everything.
Oak leaves carry the same tannins as the acorns, and green spring leaves carry far more than the dry brown ones that fall in autumn. A dog who chews a leaf or two is not a concern. A dog who systematically strips and eats oak leaves, or who eats leaf litter in volume, is getting a repeated exposure and that is worth raising with us.
My dog has been eating acorns daily for two weeks and seems completely well.
Please book him in this week. This is the exact pattern that produces the kidney version of this, and the reason it catches people out is that nothing looks wrong until the point where quite a lot is. A set of bloodwork and a urine sample will tell us whether anything is happening, and if the answer is nothing, you have a baseline and a reason to break the habit now.
Can squirrels eating them mean they are safe?
No. Squirrels process tannins in a way dogs cannot, and they also cache acorns for months to let the tannins leach out before eating them. Watching wildlife eat something tells you nothing useful about your dog.
My dog is coughing and gagging after picking something up on a walk.
Phone us and set off. Coughing, gagging, pawing at the mouth or distressed breathing after picking something up can mean an object in the airway rather than in the stomach, and that is a different order of urgency. If your dog cannot breathe, cannot make a sound and cannot cough, head for us or the nearest open emergency hospital immediately and phone from the road.
Speak to the team at Lougheed Animal Hospital
If your dog has swallowed a conker, eaten acorns in quantity, or is unsteady after a walk under the trees, phone us before you set off so we can tell you whether to come here or go straight to an emergency hospital. Outside our hours, go to the nearest open emergency hospital and have a passenger call ahead.
Published by the team at Lougheed Animal Hospital.
This article is educational in nature and is not a replacement for hands-on assessment of your own pet by a veterinarian.
Lougheed Animal Hospital
108-32423 Lougheed Highway, Mission, BC V2V 7B8
Phone: (604) 826-7066
Hours: Monday to Friday 8:00 AM to 7:00 PM; Saturday and Sunday 9:00 AM to 4:00 PM; statutory holidays closed