Horse Chestnut Poisoning in Dogs

The Aesculus hippocastanum, more commonly referred to as the horse chestnut tree, is grown in temperate areas around the world. These trees can reach nearly 120 feet tall and contain aesculin, a neurotoxic glycoside that can cause gastrointestinal distress, disorientation, spasms, and in higher doses can even result in death. The entire plant is known to have an extremely unpleasant flavor so large enough quantities to induce central nervous system related symptoms are rarely consumed. If your canine companion has eaten any part of the horse chestnut tree, contact your veterinarian for further treatment instructions.

The toxic element of the horse chestnut tree is a neurotoxic glycoside called aesculin. In low doses it causes gastrointestinal distress, and at higher doses it can affect the central nervous system.

Symptoms of poisoning from the horse chestnut tree generally occur within one to six hours after ingestion of any part of the plant and can continue to be seen for up to two days afterwards. 

• Coma
• Depression
• Diarrhea
• Dilated pupils
• Drooling
• Excessive drooling
• Extreme thirst
• Hyperactivity
• Lack of coordination
• Lethargy
• Loss of appetite
• Muscle twitching
• Paralysis
• Seizures
• Sudden death
• Tremors
• Vomiting

Types

Additional complications that can arise from consuming horse chestnuts or conkers:

Bowel obstruction- If the hard nuts are eaten they may prevent the passage of food through the intestinal tract, in addition, if this condition is not corrected it may cause decreased blood flow to the bowels leading to necrosis of the tissues. 

Choking hazard- If your pet appears to have an obstruction in their throat but is not in immediate danger contact your veterinarian for emergency instructions. Some actions may do more harm than good if your pet is not actually choking or if done incorrectly. If the situation is life-threatening you may want to perform the appropriate first aid until you are able to reach a veterinarian.

The major toxic component in this tree is a neurotoxic glycosidic saponin called aesculin. Aesculin is found in all parts of the tree including the leaves and nuts which are often found under the tree. Severe poisoning from horse chestnuts is fairly rare as Aesculin is poorly absorbed by the body so toxicity requires the ingestion of moderate to large amounts of plant material. The unpleasant flavor of this plant usually prevents the large enough quantities for neurotoxicity from being ingested, although signs of gastrointestinal distress such as vomiting and diarrhea may occur at lower dosages. 

The chestnut of the tree is contained in a distinctive green, spiky capsule until the nuts inside ripen and the capsule splits open spilling the nuts on the ground. These nuts are also known as “conkers”. Puppies are at particular risk of poisoning from playing with these fallen chestnuts as they tend to explore the world with their mouths. 

Horse chestnut is also used as an herbal remedy for circulatory system disorders and diseases for humans. If you are using horse chestnut as an herbal remedy, make sure that you keep the supplements well out of reach of your pets.

Witnessing ingestion of any part of the horse chestnut tree, including the nuts that have fallen from the tree, is often enough to generate a preliminary diagnosis when combined with the symptoms and signs of aesculin poisoning. If the consumption of the plant was not witnessed your veterinarian is likely to recommend a visit to the office based on the symptoms described. Your veterinarian will ask questions regarding any opportunities for inappropriate eating and prescriptions or supplements your dog may be taking. Horse chestnut interacts with several other medications and chemicals so this information may be helpful in determining the course of treatment. A biochemistry profile, complete blood count, and urinalysis will be ordered to reveal toxins and imbalances. Any stomach contents from vomiting will also be analyzed in order to add credence to the preliminary diagnosis. Material from the horse chestnut tree may be observed in the vomit, further confirming the diagnosis.

It is always wise to contact your veterinarian before starting treatments to get specific instructions for your pet and to determine if either the amount eaten or the reaction to the toxin warrants a visit to the veterinarian’s office. If only small amounts of plant material were consumed by your pet, the symptoms will generally be related to gastrointestinal upset. If your pet has not yet vomited and the ingestion was recent you may be given instructions on the proper way to induce vomiting. This is to prevent as much of the toxin from reaching the bloodstream as possible. In the case of larger ingestions, hospitalization is generally recommended. Although there is no current antidote to aesculin poisoning, supportive measures can help reduce symptoms and speed healing. IV fluid treatment will be administered at the veterinarian’s office to prevent dehydration and medications such as Imodium or Pepcid AC may also be recommended for their gastroprotective properties. Anti-emetics may also be given to reduce the severity of any vomiting.

In most cases the prognosis for horse chestnut poisoning is good. Gastric effects usually disappear within a few hours and neurological symptoms generally clear up within a few days with proper supportive treatment. If your pet continues to vomit even after the poison has cleared the system withholding food until the vomiting and diarrhea have ceased for at least 12 hours may be recommended to give the dog’s stomach muscles time to recover from the violent gastric spasms. Because this toxin can cause injury to your dog’s kidneys an appointment may be recommended to ensure that the functioning has not been negatively affected.