Pencil Cactus Poisoning in Dogs

The Euphorbiaceae family of plants has many branches that cause a toxic reaction when trimmed and the sap spills out, or in the case of pets, when the plant is bitten into. Most of the documentation available refers to human poisoning by pencil cactus, but the risk is indeed there if you have this plant in your garden within reach of a curious pet.

The pencil cactus will cause immediate pain when bitten into which serves as a deterrent for large ingestions of the plant. However, the dermal, and particularly the ocular damage that has been recorded in humans can easily be related to the animal species if exposed to the plant’s toxic sap. Many gardeners will plant the pencil cactus in their yards in order to deter wildlife; some wildlife may be wise to the dangers of the plant while others will suffer the consequences of contact. 

The euphorbia tirucalli is a cactus-like tree but does not have the spiny needles characteristic of a true cactus. Milky sap can be released from any part of the plant, resulting in symptoms like stomach pain upon ingestion or burning of the eyes if the exposure is of an ocular nature.

The pencil cactus plant is a member of the genus Euphorbiaceae. There are over 1600 species of this family worldwide. The pencil cactus, known as Euphorbia tirucalli, is toxic to humans and dogs worldwide as it contains a milky substance capable of causing serious gastrointestinal, ocular, and dermal injury.

Of the Euphorbiaceae genus, the pencil cactus, or Euphorbia tirucalli, is thought to be one of the most dangerous when it comes to exposure. Despite this, the effects on your pet may be of a mild to moderate toxicity if your dog is warned off with a single bite as opposed to a large ingestion. You may see the following signs of distress in your pet if he comes into contact with the pencil cactus.

Ocular Contact

• Pain
• Swelling
• Redness
• Ulceration
• Temporary or permanent blindness (some humans have experienced permanent blindness)

Dermal Contact (there can be a delay in dermal symptoms)

• Burning
• Blisters
• Rash accompanied by pain
• Irritation to the skin

Ingestion

• Stomach pain
• Vomiting
• Nausea
• Diarrhea

Types

There are thousands of types of plants in the Euphorbia genus. The pencil cactus is also commonly called the following names.

• Milkbush
• Pencil tree
• Finger tree
• Rubber Euphorbia
• Indian spurge tree

• It is thought that diterpene esters are the noxious substance in the sap which is also called latex
• The sap has acidic properties
• The pencil cactus has excessive amounts of sap
• The plants grow well in many conditions allowing for spread
• The taste is unappealing which is why most exposure cases are limited to dermal and ocular
• Your pet may rub the sap from his paw into his eyes
• Your dog can ingest the sap from biting the plant or from licking the sap off the fur

The history that you can provide about the exposure to the pencil cactus will be an important part of the diagnostic process. If you witnessed the event, or have returned home to find your pencil cactus broken and chewed with sap oozing out of the plant, bring a sample of the plant to the clinic to aid in the diagnosis. Be careful to handle the pencil cactus with care and caution as there have been numerous reports of eye irritation from this particular Euphorbia species upon handling. If you have an estimate of the time that the plant may have been explored by your pet, this will be helpful information as well. It should be noted that dermal exposure to the plant can sometimes result in a delayed reaction but it is best not to wait for symptoms to appear before taking your pet to the veterinarian in any case of plant ingestion or exposure.

The veterinary team will perform examinations of dermal, ocular and oral types. Your dog may need an extensive eye examination to verify if there has been corneal damage or burning that needs immediate attention. Blood and urine tests will also be done to see how your dog is handling the toxic effects of the pencil cactus poisoning, and to check for any underlying conditions that may be affected by the event.

Your dog will be carefully attended to by the veterinary team as they determine the extent of the pencil cactus poisoning. The therapy may include the following steps.

Dermal

Your dog’s skin and fur will be gently washed to remove the sap from the skin. If pain is present, medication may be administered.

Ocular

The veterinary will use a solution to wash the eye and soothe the pain. Because ocular exposure can be extensive there may be a need for further testing by a specialist. This is determined case by case and depends on the amount of latex sap that reached the eye directly.

Oral

Most incidences of pencil cactus poisoning do not involve heavy oral exposure but if your pet did ingest the plant and is vomiting continuously, there is risk of dehydration. Some dogs who eat quantities of the plant despite the pain and taste may need intravenous for the administration of pain medication for the stomach or antiemetics for extreme nausea. Fortunately, this is a rare occurrence.

The recovery of pencil cactus in dogs is most often due to a dermal or ocular contact. The prognosis is good unless the sap has caused damage to the eyes that may require time to heal. There is the risk of permanent damage to the eyes, and if this is the case, patience on your part as your pet adjusts to a new lifestyle will be necessary. The veterinary team will be available to assist you with questions you may have when attending follow-up appointments. Removal of this plant from your garden may be the best choice; at the very least block access to this plant for all children and animals.