Autumn is one of my favourite times of year for walking dogs around Finchley and North London. The cooler weather, changing leaves and interesting new smells make woodland walks particularly enjoyable.

But autumn also brings two easy-to-overlook hazards: conkers and acorns.

Both are common in parks, gardens and woodland. They may look harmless, especially to anyone who remembers collecting conkers as a child, but neither is safe for dogs to eat.

I’ve been walking dogs professionally since 2011, and one thing I always keep an eye on in autumn is what a dog is investigating among the fallen leaves.

Dogs should be able to enjoy sniffing and exploring. We just need to recognise what could harm them.

In this guide, I’ll explain why conkers and acorns are dangerous, what symptoms to watch for and how to reduce the risk without spoiling your dog’s autumn walks.

Updated October 2026.

Quick answer: Are conkers and acorns poisonous to dogs?

Yes. Both conkers and acorns are poisonous to dogs if eaten.

Conkers contain aesculin, a substance that can cause poisoning. Acorns contain tannins, which can cause digestive problems and, in severe cases, damage to internal organs.

Both can also cause choking or a blockage in the digestive system.

Although serious poisoning is uncommon, never assume eating one is harmless.

If you think your dog has swallowed a conker or acorn, contact your vet straight away, even if your dog appears perfectly well.

Do not wait for symptoms to develop.

What’s the difference between conkers and acorns?

Although they often appear in the same season, conkers and acorns come from different trees.

Conkers

Conkers come from horse chestnut trees.

They are generally smooth, shiny and brown, and develop inside a green, spiky outer case.

Horse chestnut trees are common in parks, gardens and along streets.

Acorns

Acorns come from oak trees.

They are usually smaller than conkers, with a characteristic cup-shaped cap at one end.

They may be green or brown, depending on their stage of development.

Both types of tree are found in North London’s parks and woodland, so it is sensible to be aware of them during autumn walks.

1. Why are conkers poisonous to dogs?

Conkers contain a naturally occurring toxic substance called aesculin.

It is found in different parts of the horse chestnut tree, including the seeds, bark and leaves.

If a dog chews or swallows conkers, they may develop gastrointestinal symptoms or other signs of poisoning.

The conker itself also presents a physical danger.

Because conkers are hard and relatively large, they can become lodged in the digestive tract and cause an obstruction.

A blockage can become a serious veterinary emergency.

Symptoms of conker poisoning

Possible signs include:

Vomiting.
Diarrhoea.
Drooling or retching.
Abdominal pain or discomfort.
Restlessness.
Unusual tiredness or lethargy.
Wobbliness or trembling.
Collapse in severe cases.

Symptoms may begin within a few hours, but some dogs do not show signs until later.

This is why waiting to see whether your dog becomes unwell is not a safe approach.

You can find further information in Blue Cross: Are Conkers Poisonous to Dogs?.

2. Why are acorns poisonous to dogs?

Acorns contain tannins, which can irritate the digestive system and cause poisoning.

The most common problems involve the stomach and intestines.

However, severe cases can affect the liver or kidneys.

Acorns can also create a physical hazard, particularly for smaller dogs, because they may become lodged in the digestive system.

Symptoms of acorn poisoning

Signs may include:

Vomiting.
Diarrhoea.
Abdominal pain.
Loss of appetite.
Dehydration.
Lethargy.
Collapse in severe cases.

The severity of the problem depends on several factors, including how much was eaten and the individual dog.

You should not assume that a large dog will be safe or that a small amount cannot cause a problem.

If your dog has eaten an acorn, seek veterinary advice promptly.

For further information, see Blue Cross: Are Acorns Poisonous to Dogs?.

3. Are green acorns more dangerous than brown acorns?

Green, unripe acorns generally contain higher concentrations of tannins than mature brown acorns.

However, that doesn’t make brown acorns safe.

Both should be kept away from dogs.

Rather than trying to judge which acorns might be more toxic, the safest approach is to prevent your dog from eating any of them.

4. Can one conker or acorn harm a dog?

Yes, potentially.

Not every dog that eats a conker or acorn will become seriously ill, but even a single swallowed object may cause problems, particularly if it becomes lodged in the digestive system.

The risk also depends on the size of the dog, the size of the object and whether it has been chewed or swallowed whole.

It isn’t possible to make a reliable assessment simply by watching your dog immediately afterwards.

If you suspect ingestion, contact your vet for individual advice.

5. What should I do if my dog eats a conker or acorn?

The most important thing is to act promptly.

Step 1: Contact your vet

Telephone your vet or an emergency veterinary service immediately.

Explain what you think your dog has eaten.

Do this even if your dog is behaving normally.

Step 2: Provide useful information

Your vet may ask:

Whether your dog ate a conker or acorn.
How many may have been eaten.
Whether they were chewed or swallowed whole.
Approximately when it happened.
Your dog’s age, breed and weight.
Whether your dog is showing any symptoms.

Don’t delay calling because you’re unsure about some of the answers.

Step 3: Follow veterinary instructions

Your vet will assess the situation and advise you on the next steps.

They may recommend an examination, monitoring under veterinary direction or treatment, depending on the circumstances.

Step 4: Don’t try home remedies

Do not attempt to make your dog vomit unless a veterinary professional specifically instructs you to do so.

Do not give salt, oil, milk or other home remedies.

These may cause additional harm or delay appropriate treatment.

If your dog is collapsing, having seizures, struggling to breathe or showing signs of severe distress, seek emergency veterinary care immediately.

For more information about recognising emergencies, visit my Dog First Aid Hub.

6. What treatment might a vet provide?

Treatment depends on what your dog has eaten, how much was swallowed and whether poisoning or an obstruction is suspected.

Your vet may recommend:

An examination and observation.
Medication to control symptoms.
Fluids to treat dehydration.
Blood tests where appropriate.
Imaging if a blockage is suspected.
Surgery in serious cases involving an obstruction.

Not every dog will require these treatments.

The important point is that your vet is best placed to assess the risk and decide what is necessary.

7. How can I stop my dog eating conkers and acorns?

Prevention is particularly important for dogs who enjoy picking things up from the ground.

Fortunately, you don’t need to stop your dog enjoying woodland walks.

Pay attention around trees

In autumn, watch for fallen conkers and acorns, especially beneath horse chestnut and oak trees.

You may need to adjust your route if large quantities are scattered across a path.

Teach a positive ‘leave it’ cue

A reliable ‘leave it’ cue can be very useful.

Start practising at home with low-value objects, rewarding your dog for choosing to move away from them.

Gradually build the skill in different environments.

Avoid shouting, frightening or punishing your dog.

The aim is to help them make a safer choice.

Practise ‘drop’ using rewards

If your dog picks something up, being able to ask them to release it can be invaluable.

I prefer reward-based exchanges, where the dog learns that giving something up leads to something positive.

Forcibly grabbing objects or chasing dogs can sometimes make them reluctant to release items.

Take a suitable toy or treats

If your dog enjoys carrying things, take a favourite safe toy on walks.

Suitable treats can also help redirect their attention and reward good choices.

Use appropriate walking equipment

A comfortable, secure harness and suitable fixed-length lead can help you guide your dog away from hazards.

A long line may be useful in an appropriate open environment, but it should be managed carefully around trees, other people and obstacles.

I don’t use retractable leads.

Consider extra support for persistent scavenging

Some dogs repeatedly swallow objects or food they find outdoors.

If this is happening regularly, speak to your vet to rule out relevant health concerns and consider support from a qualified reward-based trainer.

A properly fitted basket muzzle, introduced positively, may help manage scavenging risks for some dogs while training continues.

It should allow the dog to pant, drink and take rewards comfortably.

8. Don’t forget the garden

Conkers and acorns are not only a problem during walks.

If you have oak or horse chestnut trees near your garden, fallen seeds may accumulate on the ground.

Check the garden regularly and remove them where practical.

Keep conker collections brought home by children out of your dog’s reach.

The same applies to autumn displays and craft projects.

If your dog tends to chew unfamiliar objects, make sure decorations and other small items are stored safely.

9. What about oak leaves and horse chestnut leaves?

Acorns and conkers aren’t the only parts of these trees that can cause problems.

Oak leaves contain tannins, while other parts of the horse chestnut tree contain aesculin.

It is sensible to discourage dogs from chewing or eating these materials.

That doesn’t mean every dog needs to avoid walking beneath oak or horse chestnut trees.

Simply remain aware of what your dog is picking up.

For broader advice about plants and seasonal hazards, see PDSA: Poisonous Plants.

10. Other autumn hazards worth knowing about

Conkers and acorns are only two of the things I watch for during autumn walks.

Other hazards include:

Wild mushrooms and fungi.
Rotting or fermenting fruit.
Mouldy discarded food.
Toxic berries and garden plants.
Broken glass hidden beneath leaves.
Slippery paths.
Potentially contaminated standing water.

I’ve brought these subjects together in my Autumn Dangers for Dogs Guide.

For practical advice on walking routes, changing weather and shorter days, see Autumn Dog Walking Tips.

Frequently asked questions

Are conkers poisonous to dogs if they only chew them?

Chewing a conker can expose a dog to its toxic substances, and fragments may be swallowed. Contact your vet if you think your dog has chewed or ingested part of a conker.

Can dogs play with conkers without eating them?

I wouldn’t recommend it. Dogs may accidentally swallow them or bite off pieces. Use a suitable dog toy instead.

Are acorns poisonous to puppies?

Yes. Puppies may be especially vulnerable to problems from swallowing objects because of their smaller size. Contact your vet if a puppy eats an acorn.

Can dogs eat brown acorns?

No. Brown acorns are not safe treats for dogs, even though their tannin content may differ from green acorns.

How quickly do symptoms appear?

Symptoms may develop within hours, although some signs can be delayed. Do not wait for symptoms before contacting your vet.

Can a conker cause an intestinal blockage?

Yes. Conkers can cause an obstruction if swallowed. This may require urgent veterinary treatment.

Should I make my dog sick if they’ve eaten an acorn?

No. Do not induce vomiting unless a veterinary professional specifically instructs you to.

Are all chestnuts poisonous to dogs?

Conkers come from horse chestnut trees and dogs should not eat them. They are different from edible sweet chestnuts. However, nuts can still present choking and digestive risks, so I wouldn’t use fallen chestnuts as dog treats.

Enjoying autumn walks in Finchley

I regularly walk dogs around Finchley, Muswell Hill and the surrounding areas, including local parks and woodland.

Autumn is a wonderful season for allowing dogs to sniff, explore and experience their surroundings.

My aim isn’t to prevent dogs from enjoying those opportunities.

It’s to provide walks that suit each individual dog while managing avoidable risks.

At Finchley Dog Walker, I offer solo, one-to-one dog walks that start and finish at the dog’s home.

I don’t combine dogs from different households or transport groups in vans.

This approach is particularly helpful when adapting walks for nervous dogs, rescue dogs and dogs who need a little more time and attention.

You can also find out about my rescue dog support.

Final thoughts

Conkers and acorns are a familiar part of autumn, but they aren’t harmless for dogs.

Both can cause poisoning, and both can create problems if swallowed.

The good news is that a little awareness goes a long way.

Keep an eye on what your dog is investigating, practise reward-based ‘leave it’ and ‘drop’ cues, and avoid using conkers or acorns as toys.

Most importantly, if you think your dog has eaten one, contact your vet straight away.

Veterinary disclaimer: I am a qualified canine first aider, not a veterinary surgeon. This article is intended to help owners recognise risks and does not replace professional veterinary advice, diagnosis or treatment. If you suspect poisoning or a digestive obstruction, contact your vet immediately.