Buxus sp.
Buxaceae
Boxwood; Box Tree; Box; Common Box; European Box; Turkish Boxwood; Dudgeon Boxwood; Buxus; Buxus spp.; Buxus sempervirens
Butyraceous, butter-like oil, and toxic alkaloids including buxine, cyclobuxine, and cycloprotobuxine. The plant has a pronounced negative effect on horses and other grazing animals, while dogs and cats most commonly develop gastrointestinal signs.
In dogs and cats, signs may include mild to severe gastroenteritis, vomiting, diarrhea, abdominal pain, cramping, drooling, lethargy, depression, and general gastrointestinal discomfort. In horses and grazing animals, symptoms may be much more severe and may include colic, diarrhea, weakness, seizures, convulsions, respiratory failure, respiratory arrest, collapse, and death.
Boxwood, Buxus spp., also known as Box Tree, Common Box, European Box, Turkish Boxwood, and Dudgeon Boxwood, is commonly used in landscaping as an ornamental hedge around houses, gardens, walkways, and formal borders. It is one of those plants that has become so familiar in residential and commercial landscaping that its toxic potential is often overlooked. The plant is noted for both its toxicity and its long historical use in traditional medicine.
Boxwood is native to western and southern Europe, southwest Asia, and northwest Africa. Introduced to the United States long ago, it has widely escaped cultivation and become naturalized in some areas. It can be found as far north as New York and as far south as Puerto Rico. Its dense evergreen foliage, tolerance of pruning, and ability to form tight hedges have made it a standard landscape plant, which also means pets, horses, and livestock may encounter clippings, fallen leaves, hedge trimmings, or accessible shrubs.
As with many toxic or potentially poisonous plants, the degree to which an individual animal is affected depends upon the part of the plant consumed, the amount consumed, the condition of the plant material, and the individual animal’s susceptibility to the toxin at hand. Some animals are considerably more susceptible than others, with horses being the most notable concern. ASPCA lists Boxwood, Buxus spp., as toxic to dogs, cats, and horses, with alkaloids identified as the toxic principle. In dogs and cats, the expected signs are vomiting and diarrhea, while in horses the listed signs include colic, diarrhea, respiratory failure, and seizures.
To date, there has been no record of human mortality from overconsumption of Box Tree. However, the constituent parts of the plant to which its toxic effects are attributed, including a butyraceous or butter-like oil and the alkaloids buxine, cyclobuxine, and cycloprotobuxine, can and have killed grazing animals such as horses. Pet Poison Helpline likewise notes that Boxwood is highly toxic to animals, particularly horses and livestock, even though recorded human deaths are lacking.
A highly toxic dose for horses has historically been described as approximately one and a half to two and a half pounds of leaves, or roughly a small percentage of body weight. The initial symptoms would be severe gastroenteritis, including vomiting in species capable of vomiting, diarrhea, obvious abdominal pain, discomfort, and colic, followed in more severe cases by convulsions, respiratory failure, respiratory arrest, and death.
Dogs and cats are less commonly associated with life-threatening Boxwood poisoning, in large part because members of Buxus tend to have a bitter, unpleasant taste that limits consumption. A dog or cat that chews a few leaves or hedge clippings may develop vomiting, diarrhea, abdominal discomfort, lethargy, or depression, but serious intoxication in household pets appears uncommon. That does not make the plant safe; it simply means the ordinary pet exposure pattern is usually gastrointestinal rather than fatal.
The risk changes substantially for horses and grazing animals. Horses may consume larger quantities when clippings are discarded into a paddock, when shrubs are accessible along a fence line, or when desirable forage is limited. Because the toxic effects in horses can progress beyond gastrointestinal upset into seizures, respiratory failure, and death, Boxwood should not be planted where horses can browse it, and trimmings should never be thrown into horse pastures, livestock pens, or areas accessible to grazing animals.
Not only toxic, the Box Tree has also found much use over the years for medicinal purposes. The alkaloids are believed to deter certain pathogens that would otherwise promote disease. To treat rheumatism and syphilis, the wood was boiled down to a decoction; to treat epilepsy and the pain of a toothache, the volatile oils were used for their sedative and narcotic effect. It also found use in early veterinary medicine as an anthelmintic to expel intestinal worms by drying and grinding the leaves to a powder and administering them orally.
Despite the well-known health risk to horses, powdered Box Tree leaves were historically used to rid them of the parasitic larvae of the botfly. In folk medicine, Boxwood was also held in high regard as an acceptable remedy for the bite of a rabid animal. These historical uses are important because they show the plant’s pharmacologic activity, but they should not be confused with safety. A plant can have medicinal history and still be dangerous when eaten by pets, horses, or livestock in uncontrolled amounts.
The practical prevention rule is straightforward: keep pets and grazing animals away from Boxwood leaves, hedge trimmings, fallen foliage, and discarded clippings. Dogs and cats that chew shrubs may develop gastrointestinal illness, while horses and livestock face a much more serious risk if enough plant material is consumed.
Immediate Response to Boxwood Ingestion
- Remove the Source: Prevent further ingestion by removing the pet, horse, or livestock animal from the Boxwood plant, hedge, clippings, leaves, branches, trimmings, or any area containing discarded plant material.
- Remove Plant Material from the Mouth: If ingestion was recent and it is safe to do so, remove visible plant material from the mouth and flush the mouth thoroughly with water.
- Identify the Animal Exposed: Determine whether the exposed animal is a dog, cat, horse, cow, goat, sheep, or other grazing animal, because the risk is much more pronounced in horses and livestock than in ordinary dog and cat exposures.
- Estimate the Amount: Determine whether the animal only chewed a few leaves, swallowed hedge clippings, ate a large amount of foliage, or had access to a pile of trimmings. Large ingestion and access to clippings are more concerning.
- Watch for Early Signs: Monitor for vomiting, diarrhea, abdominal pain, cramping, lethargy, depression, colic, weakness, or signs of gastrointestinal distress.
- Contact Veterinary Help: Consult a veterinarian, emergency veterinary clinic, ASPCA Animal Poison Control, or Pet Poison Helpline if symptoms are present, if the amount is unknown, if a horse or livestock animal was exposed, or if a pet is young, elderly, pregnant, very small, or medically fragile.
Inducing Vomiting and Decontamination
- Getting Plant Material Out Matters: If a dog has recently swallowed Boxwood, removing remaining plant material from the stomach may reduce continued exposure to alkaloids and gastrointestinal irritants. In appropriate dog exposures, vomiting may be one of the least disruptive ways to remove recently ingested leaves or clippings before additional toxin is absorbed.
- Inducing Vomiting in Dogs Only: If ingestion was recent and the dog is alert, breathing normally, able to swallow, and not showing weakness, collapse, seizures, severe depression, repeated vomiting, respiratory distress, or neurologic signs, a veterinarian or animal poison-control professional may recommend inducing vomiting with fresh 3% hydrogen peroxide.
- Cat Warning: Hydrogen peroxide should not be used to induce vomiting in cats unless a veterinarian specifically directs it. Cats are more prone to irritation and complications from hydrogen peroxide, and home vomiting attempts may create more risk than benefit.
- Do Not Induce Vomiting in an Unstable Animal: Vomiting should not be attempted in any animal that is weak, collapsed, sedated, having trouble breathing, unable to swallow normally, already vomiting repeatedly, seizing, showing neurologic signs, or otherwise unstable.
- Veterinary Decontamination: If a large amount was ingested, if symptoms are already present, or if the exposed animal is a horse or livestock animal, a veterinarian may consider gastric lavage, activated charcoal, cathartics, fluid therapy, or other decontamination and stabilization measures depending on the species, amount, timing, and clinical signs.
Dogs and Cats: Supportive Care
- Expected Course: In dogs and cats, the likelihood of death or serious negative effects is rare. Most often, symptoms are limited to lethargy, vomiting, diarrhea, abdominal discomfort, and gastrointestinal upset.
- Hydration: Ensure the pet receives adequate fluids to reduce the risk of dehydration caused by vomiting or diarrhea.
- Gastrointestinal Monitoring: Pets with repeated vomiting, persistent diarrhea, blood in stool, abdominal pain, refusal to eat, weakness, or dehydration should be evaluated by a veterinarian.
- Symptomatic Care: The vast majority of dogs and cats are expected to make a full recovery with symptomatic treatment once further ingestion is prevented and gastrointestinal signs resolve.
Horses and Grazing Animals: Emergency Concern
- Higher-Risk Species: In grazing animals, especially horses, the effect of Boxwood toxins is much more pronounced and potentially lethal.
- Serious Signs: Colic, diarrhea, weakness, seizures, convulsions, respiratory failure, respiratory arrest, collapse, or severe depression should be treated as emergency signs.
- No Reliable Antidote: Unfortunately, there is no specific or reliable antidote for Boxwood poisoning. Treatment is largely symptomatic and supportive.
- Veterinary Treatment: Veterinarians may use treatments that have proved valuable in other plant alkaloid poisonings, along with respiratory support, seizure control, fluid therapy, gastrointestinal support, and monitoring as needed.
- Prognosis: Recovery will depend largely on the severity of the poisoning, the amount ingested, the time to treatment, and the individual animal’s susceptibility to the toxins.
Landscape and Pasture Prevention
- Do Not Feed Clippings: Never throw Boxwood trimmings, hedge clippings, or pruned branches into horse pastures, livestock pens, or areas accessible to grazing animals.
- Fence Line Risk: Keep Boxwood hedges outside areas where horses or livestock can browse through fencing or reach fallen leaves.
- Pet Access: Dogs that chew shrubs, puppies, and curious pets should be kept away from Boxwood hedges, especially after pruning when loose leaves and clippings are abundant.
- Remove Fallen Material: Clean up clippings, fallen leaves, and storm-damaged branches promptly to reduce accidental ingestion.
Prognosis and Recovery
- Dogs and Cats: Prognosis is generally good when exposure is limited and signs are restricted to vomiting, diarrhea, lethargy, or mild gastrointestinal upset.
- Horses and Livestock: Prognosis is more guarded in horses and grazing animals because severe poisoning may progress to seizures, convulsions, respiratory failure, respiratory arrest, and death.
- Severity Depends on Exposure: Outcome depends on the amount consumed, animal species, individual susceptibility, timing of treatment, and whether severe neurologic or respiratory signs develop.
- Prevention: Prevent further access to the plant, remove any plant material still in the mouth, clean up clippings, and seek veterinary care promptly when significant exposure is suspected.