Conkers are the seeds of the horse chestnut tree. This is a common tree in parks, streets and gardens in the UK the National Forest Inventory recorded 470,000 horse chestnuts in 2018.
The conkers drop to the ground in September and October. They are encased in a green, prickly covering. The cases dry out over a few days and expose the glossy brown conkers. Inquisitive or greedy dogs may eat them or play with them as they forage on walks. They taste bitter so most dogs will only eat one. However, they are often swallowed if they are thrown in a game or if the dog is playing with them.
It is important to be alert to the ingestion of conkers as they can cause severe illness. They are toxic to dogs and present a choking hazard, as well as a risk of obstruction of the digestive tract.
The conkers, leaves and bark of the horse chestnut tree contain a toxic chemical called aesculin. A dog would usually need to eat several conkers to ingest a high enough dose to cause symptoms.
Symptoms of aesculin poisoning can take 2 days to appear. More often, the dog starts to appear unwell 1-6 hours after the conkers are eaten. Initially, dogs appear restless and uncomfortable as they have a painful abdomen. Vomiting and diarrhoea usually follow. Vomiting may be severe and blood may be present. Aesculin toxicity goes on to cause disorientation, weakness, collapse and muscle tremors. Depending on the dose of poison ingested the symptoms can progress to respiratory paralysis and death. It is essential that emergency veterinary treatment is sought as soon as possible when these symptoms are seen. If you witness your dog eating several conkers, seek veterinary attention.
There is no known antidote to aesculin. The vet will reduce the amount of toxin in the body by inducing vomiting or flushing the stomach under sedation or anaesthesia. If the conkers have not been chewed then inducing vomiting must be considered carefully, as conkers can get stuck in the oesophagus (tube from the mouth to the stomach). Intravenous fluid therapy may be used to prevent dehydration caused by vomiting and speed up the removal of the toxin.
Conkers are often the perfect size to become stuck in the back of the throat. This usually occurs when a conker is caught by a dog in a game. Your dog may paw at their mouth and cough repeatedly. As the airway is obstructed the dog becomes distressed with laboured breathing and may collapse. Pick your dog up if you are able to do so, as you need to get your dog to a vet immediately. Incline the head down or attempt a wheelbarrow position, quickly picking up the hindlegs to attempt to dislodge the conker. Any attempt to dislodge the conker manually may push it further or result in a badly bitten hand so only attempt this if it is safe. Take your dog to a veterinary practice immediately. Your dog will be given oxygen and anaesthetised or sedated to remove the obstruction.
Your dog may swallow a conker without difficulty but then it can become lodged in the oesophagus. Usually they drop their head, retch, repeatedly swallow and drool. If your dog cannot dislodge the conker and recover quickly then you need to contact your vet. The wall of the oesophagus can be damaged if conker removal is not performed quickly. This is a rare complication but can occur with any small ingested object. It is more common with bouncy balls, childrens’ toys and bones.
Conkers which reach the stomach can block the stomach outflow or the intestines. The obstruction can be partial or total. The dog may vomit repeatedly, unable to keep food and sometimes water down. If a partial obstruction is present the vomiting may be intermittent. If you suspect your dog has an obstruction an emergency veterinary visit is indicated. The vet will take a history and examine your dog. In lean dogs the conker may be felt on palpation of the abdomen. More commonly, investigation with x-ray and ultrasound is necessary to diagnose obstruction. Treatment is surgery to remove the obstruction. Parts of the intestine may need to be removed if they are damaged by the obstruction. This usually occurs when the obstruction has been present for some time.
Most dogs will only try eating a conker once and spit the bitter remnants out. Some dogs may be less discriminating. Carry a toy or treats to distract them from conkers. Throwing conkers for dogs to catch and play with is best avoided.