Are Conkers and Acorns Poisonous to Dogs?

Updated August 2026

Summary: Conkers and acorns can both make dogs unwell when chewed or swallowed. Conkers contain aesculin, while acorns contain tannins. Both can cause vomiting, diarrhoea, abdominal discomfort and loss of appetite. Their size and hardness also create choking and intestinal blockage risks. Serious poisoning is uncommon, but you should contact your vet promptly if your dog eats one. Do not wait for symptoms or try to make your dog vomit.

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Autumn walks bring cooler temperatures, changing colours and plenty of new smells for dogs to investigate.

They also bring conkers and acorns.

These can be found under trees in parks, gardens, residential streets and wooded areas throughout Finchley, Muswell Hill and North London.

Most dogs will sniff them and move on. Puppies, scavengers and dogs who enjoy carrying round objects may pick them up, chew them or swallow them.

That is where the danger begins.

Are conkers and acorns poisonous to dogs?

Yes. Both can make dogs unwell.

Conkers contain a substance called aesculin. Acorns contain tannins, sometimes described as tannic acid.

The severity depends on several factors, including:

• what your dog ate
• how much they ate
• whether it was chewed
• the size of your dog
• when it happened
• your dog’s health
• whether pieces have become lodged in the digestive system

There is no reliable number of conkers or acorns that can be described as safe.

The British Small Animal Veterinary Association advises owners to contact their vet immediately if they suspect their dog has eaten a conker or acorn.

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

Contact your vet promptly, even if your dog appears completely normal.

Do not wait for vomiting, diarrhoea or other symptoms to begin.

Take these steps

1. Prevent your dog from eating anything else.
2. Move away from the area.
3. Contact your vet or emergency veterinary service.
4. Tell them whether your dog ate a conker, acorn or both.
5. Estimate how many may have been eaten.
6. Explain whether they were swallowed whole or chewed.
7. Tell the vet when it happened.
8. Provide your dog’s approximate weight and any relevant health conditions.
9. Take a photograph or safely collect a sample if you are uncertain what was eaten.
10. Follow the veterinary advice you are given.

If your dog is collapsing, choking, having difficulty breathing, fitting or showing severe pain, contact an emergency vet immediately.

Do not try to make your dog vomit

Do not give salt water, hydrogen peroxide, mustard, or any other home remedy.

Trying to make a dog vomit without veterinary guidance can cause further injury or poisoning. It may also be unsafe when a hard object has been swallowed.

Only a veterinary professional should decide whether inducing vomiting is appropriate.

Animal PoisonLine also advises owners not to attempt to induce vomiting in their pet.

Animal PoisonLine

If you are unsure whether your dog needs emergency treatment, you can contact Animal PoisonLine on 01202 509000.

It is a paid, 24-hour UK telephone service run by the Veterinary Poisons Information Service. Its specialists can assess what your pet has been exposed to and advise whether veterinary treatment is required.

If your dog is already showing collapse, convulsions or breathing difficulties, contact your vet immediately rather than calling the poison line first.

Why are conkers dangerous to dogs?

Conkers are the seeds of the horse chestnut tree, Aesculus hippocastanum.

They are usually shiny and reddish-brown. They fall inside green or brown spiky cases during autumn.

All parts of the horse chestnut tree contain aesculin, including:

• conkers
• leaves
• bark
• flowers

The greatest everyday risk for most dogs comes from chewing or swallowing the conkers found on the ground.

The Kennel Club’s veterinary guidance on conkers explains that aesculin can cause sickness and stomach problems. Larger amounts may cause more serious effects, although severe cases are rare.

Conkers also create physical risks

Conkers are hard, smooth and often the right size for a dog to swallow.

They can cause:

• choking
• damage while being chewed
• an obstruction in the stomach
• an obstruction further along the intestines

A conker does not have to cause toxic effects to create a veterinary emergency. A swallowed conker may become stuck and prevent food or fluid from moving normally through the digestive system.

Symptoms after eating conkers

Possible symptoms include:

• vomiting
• diarrhoea
• drooling
• abdominal discomfort
• reduced appetite
• restlessness
• lethargy
• trembling
• unsteady movement

A dog with an obstruction may also show:

• repeated vomiting
• refusal of food
• abdominal pain
• a tense or swollen abdomen
• difficulty passing faeces
• unusual tiredness
• repeated attempts to settle
• a hunched or uncomfortable posture

Do not use this list to decide whether veterinary advice is necessary.

If you know or suspect that a conker has been swallowed, contact your vet before symptoms develop.

Why are acorns dangerous to dogs?

Acorns are the fruit of oak trees.

They contain tannins that can irritate the digestive system and make dogs unwell.

Green, unripe acorns generally contain higher concentrations of tannins than mature brown acorns. That does not make brown acorns safe.

The Blue Cross guide to acorns and dogs explains that acorns can cause stomach problems and physical damage when eaten.

Eating larger quantities of acorns or eating them repeatedly may increase the risk of more serious liver or kidney problems.

Like conkers, acorns can also cause an intestinal blockage.

Symptoms after eating acorns

Possible signs include:

• vomiting
• diarrhoea
• reduced appetite
• lethargy
• drooling
• abdominal pain
• irritation or swelling around the mouth
• blood in vomit or faeces
• increased thirst
• changes in urination

Serious effects are not inevitable, but you cannot judge the risk by looking at your dog alone.

Contact your vet if an acorn has been eaten.

How soon will symptoms appear?

Stomach-related symptoms may begin within a few hours.

Other problems may take longer to become apparent. An obstruction can develop after the initial incident, particularly if a conker or a large piece has moved into the intestines.

This is why waiting to see whether your dog becomes ill is not a safe plan.

Early advice gives your vet more options and helps them assess the risks before the situation becomes more complicated.

Is one conker or acorn dangerous?

One conker or acorn does not automatically mean a dog will become seriously ill.

However, it may still:

• cause a stomach upset
• become a choking hazard
• lodge in the digestive system
• affect a small dog more severely
• create complications if it was chewed into sharp pieces

The amount of toxin can vary between individual conkers and acorns. Dogs also differ in size, health and sensitivity.

There is no useful online calculation that can confirm your dog is safe.

Call your vet and let them assess the individual situation.

What if my dog only chewed it?

Contact your vet for advice.

Chewing may release more of the substances inside the conker or acorn. Your dog may also have swallowed pieces without you seeing them.

Tell your vet:

• what was chewed
• how much remains
• whether pieces appear to be missing
• when it happened
• whether your dog has any symptoms

Do not assume that a damaged conker or acorn means nothing was swallowed.

Are conkers the same as sweet chestnuts?

No.

Conkers come from horse chestnut trees. Sweet chestnuts come from a different tree.

This article is concerned with horse chestnut conkers and acorns from oak trees.

Even when a nut is not considered toxic, it may still cause choking, digestive upset or a blockage. Do not encourage your dog to eat unidentified nuts, seeds or their outer casings.

Should dogs play with conkers?

No.

Conkers may look like convenient natural balls, but they are not dog toys.

Do not:

• throw conkers for your dog
• kick them along the path
• encourage your dog to catch them
• let children use them in games involving the dog
• leave collected conkers within reach at home

A dog who begins by carrying a conker may eventually chew or swallow it.

Use a suitable dog toy instead.

What I watch for on autumn walks

Fallen leaves can make conkers and acorns difficult to see.

On autumn walks around Finchley and Muswell Hill, I pay particular attention beneath mature trees and where nuts have collected along the edges of paths.

For a dog who likes scavenging, I may:

• scan the ground ahead
• shorten the lead temporarily
• move around a heavily covered area
• reward the dog for checking in
• use a familiar “leave it” cue
• offer a safe swap when something has been picked up
• choose a clearer route
• keep the dog on a suitable long line attached to a harness

The aim is not to stop the dog sniffing.

It is to give them safe opportunities to explore without risking swallowing something harmful.

My Autumn Dog Walking Tips cover fungi, darker evenings, fallen leaves, seasonal illness and other changing risks.

Teach “leave it” before you need it

“Leave it” means not picking something up.

Begin indoors with an object that is not particularly exciting. Reward your dog for moving away from it or choosing to look at you instead.

Gradually practise around slightly more tempting objects and in different environments.

Do not begin beside a pile of conkers. Training is more effective when the first stages are easy.

My Dog Training Hub offers reward-based guidance to build useful everyday skills.

Teach a safe “drop it” or swap

“Drop it” is used after your dog has already picked something up.

Avoid chasing your dog or immediately grabbing at their mouth. That can encourage them to run away, swallow quickly or begin guarding found objects.

Instead:

1. Stay calm.
2. Offer a higher-value reward.
3. Allow the dog to release the object.
4. Reward them.
5. Move away from the hazardous area.

Practise with ordinary toys before trying to use the cue in a real emergency.

If your dog freezes, stiffens, growls or guards stolen items, do not risk being bitten. Create space and seek help from a qualified reward-based trainer or behaviour professional.

Use management as well as training

Training takes time.

While your dog is learning, management prevents them from repeatedly practising scavenging.

Useful options may include:

• a fixed-length lead
• a well-fitted harness
• a long line attached to a harness
• walking at quieter times
• avoiding heavily covered areas
• carrying suitable rewards
• positively training your dog to wear a basket muzzle

A waterproof long line on Amazon may provide controlled freedom for a dog who is not ready to be off lead. A long line should be attached to a well-fitted harness, not the collar.

A silicone treat pouch on Amazon can make it easier to reward a quick check-in or practise a swap without fumbling through pockets.

Equipment does not replace observation or training.

Do not use a retractable lead, choke chain, slip lead, prong collar, or any other aversive tool to stop scavenging.

Can a basket muzzle help a scavenging dog?

A well-fitted basket muzzle may be a sensible safety measure for a dog who repeatedly swallows dangerous objects.

The dog must still be able to:

• pant fully
• drink
• take rewards
• breathe comfortably
• move their jaw
• wear it without rubbing or distress

A muzzle should be introduced gradually using rewards. It should never be pushed onto a frightened dog immediately before a walk.

The Dogs Trust muzzle-training guide explains how to build a positive association in manageable stages.

A muzzle prevents access to some items. It does not teach the dog how to feel or what to do; instead, continue with appropriate training and management.

Make the garden safer

If you have an oak or horse chestnut tree in or beside your garden:

• check the ground regularly
• collect fallen conkers and acorns
• check beneath fallen leaves
• keep dogs away while clearing them
• dispose of collected nuts securely
• supervise puppies and known scavengers
• prevent access to bags or buckets of collected conkers
• speak to your vet if your dog repeatedly eats non-food items

Wind can carry conkers and acorns into gardens even when the tree is outside your boundary.

My guide to plants poisonous to dogs covers additional garden risks, including bulbs, berries, compost and toxic plants.

Be careful when children collect conkers

Conker collecting is a familiar autumn activity.

Once conkers have been brought home:

• keep them out of the dog’s reach
• do not leave them in open bags on the floor
• check coat pockets
• clear them away after craft activities
• make sure children understand that conkers are not dog toys

The same applies to acorns gathered for crafts, displays or wildlife projects.

Puppies and newly adopted dogs

Puppies explore with their mouths and may investigate anything they find on the ground.

A newly adopted dog may also have scavenging habits you do not yet understand.

During the first autumn together:

• use a lead or long line
• watch what they investigate
• carry suitable rewards
• practise easy swaps at home
• avoid overwhelming walking environments
• do not assume they know “leave it”
• check the garden before toilet breaks

A dog does not need to be deliberately disobedient to pick something up. They may simply be curious, hungry, excited or unfamiliar with the object.

Can enrichment stop scavenging?

Appropriate enrichment can help meet a dog’s need to sniff, search and explore.

It does not guarantee they will ignore food or objects on the ground.

A dog who loves searching may benefit from safe scent games at home, but you must still manage outdoor risks.

Read my Dog Enrichment Guide for activities based on sniffing, choice, problem-solving and rest.

Other autumn hazards to watch for

Conkers and acorns are only part of the autumn picture.

Other potential risks include:

• wild mushrooms and toadstools
• mouldy fallen fruit
• rotting leaves
• yew berries and foliage
• autumn crocus
• discarded food
• darker walking conditions
• fireworks
• seasonal canine illness
• wet and slippery surfaces

Read The Dangers of Dogs and Mushrooms if your dog investigates fungi.

My Seasonal Pet Safety Guide brings together practical advice for different times of year.

Dog poisoning and first aid guidance

First aid does not mean treating poisoning yourself.

It means:

• moving your dog away from further danger
• contacting the correct professional
• providing clear information
• following veterinary instructions
• transporting your dog safely if asked

My Dog Health and First Aid Guide explains how to prepare for everyday emergencies.

How I manage autumn risks during solo walks

Every dog investigates the environment differently.

One dog may walk past a carpet of acorns without noticing. Another may try to pick up every object along the path.

During a solo walk, I can adapt:

• the route
• the pace
• lead length
• distance from hazards
• the rewards used
• how much time the dog spends sniffing
• whether an area is suitable that day

There are no group dogs competing for food or found objects. I can focus on the individual dog and what is happening around them.

My solo dog walks in Finchley and Muswell Hill start and finish at your door. There are no vans, group collections or pressure to match another dog’s pace.

Contact me about calm, one-to-one dog walking or WhatsApp me on 07707 763344.

Want more practical seasonal dog-safety advice?

The Finchley Dog Owner’s Practical Handbook is being developed to bring together useful health, safety, walking, and everyday care information in one place.

Insert Kit email and handbook sign-up form here

Frequently asked questions

Are conkers poisonous to dogs?

Yes. Conkers contain aesculin, which can cause vomiting, diarrhoea, drooling, abdominal discomfort and other symptoms. Their size and hardness also create choking and intestinal blockage risks.

Are acorns poisonous to dogs?

Yes. Acorns contain tannins that may cause stomach problems. Larger or repeated amounts may affect the liver or kidneys. Acorns may also cause a blockage.

Are green acorns more poisonous than brown acorns?

Green acorns generally contain higher concentrations of tannins. Brown acorns are still not safe for dogs to eat.

How many conkers will make a dog ill?

There is no reliable number. The amount of aesculin varies, and the risk also depends on the dog’s size, health and how much was chewed or swallowed.

What should I do if my dog eats one conker?

Contact your vet promptly. One conker may still cause stomach problems, choking or an obstruction, particularly in a smaller dog.

What if my dog ate an acorn but seems fine?

Contact your vet for advice. Do not wait for symptoms. Some effects can be delayed.

How quickly do symptoms begin?

Vomiting, diarrhoea and abdominal discomfort may begin within hours. Problems associated with an obstruction may develop later.

Can a dog die after eating conkers or acorns?

Severe poisoning is uncommon, but serious complications can occur. Choking and intestinal obstruction can also become life-threatening without treatment.

Can dogs safely carry conkers?

It is safer not to encourage it. A dog carrying a conker may begin chewing or accidentally swallow it.

Should I make my dog vomit?

No. Do not attempt to make your dog vomit unless a veterinary professional specifically directs and supervises the appropriate treatment.

Can “leave it” prevent scavenging?

A well-taught “leave it” cue can help, but it is not infallible. Continue managing the environment with a suitable lead, harness, route choice and close supervision.

Is a muzzle cruel for a scavenging dog?

A correctly fitted basket muzzle, when introduced positively, can be a humane safety tool. The dog must be able to pant, drink and take rewards. A fabric grooming muzzle is not appropriate for normal exercise.

Related guides

• Autumn Dog Walking Tips
• Seasonal Pet Safety in Finchley
• Dog Health and First Aid Guide
• Plants Poisonous to Dogs
• The Dangers of Dogs and Mushrooms
• Dog Training Hub
• Dog and Pet Care Guides

Final reminder

Conkers and acorns are familiar signs of autumn, but neither should be treated as a dog toy or snack.

Keep an eye on the ground, practise safe reward-based cues and manage known scavengers with appropriate equipment.

If your dog eats a conker or acorn, contact your vet promptly.

Do not wait for symptoms and do not attempt a home treatment.

Veterinary disclaimer

I am a professional dog walker with an Ofqual Level 3 Canine First Aid qualification, but I am not a veterinary surgeon.

This article provides general educational information and is not a substitute for veterinary advice, diagnosis or treatment. Under the Veterinary Surgeons Act 1966, veterinary diagnosis and treatment must be carried out by an appropriately qualified veterinary professional.

If your dog has eaten a conker, acorn or another potentially harmful item, contact your vet or an emergency veterinary service promptly.