Pothos, scientifically known as Epipremnum aureum, is a highly popular trailing houseplant celebrated for its resilience and attractive, heart-shaped leaves. From a botanical perspective, its toxicity stems from the presence of insoluble calcium oxalate crystals, which are microscopic, needle-like structures found throughout all parts of the plant. These crystals are a natural defense mechanism for the plant, deterring herbivores from consuming its foliage. When the plant tissue is chewed or broken, these raphides are released, causing immediate physical irritation to the soft tissues of the mouth and digestive tract.
The primary toxicological action is mechanical and chemical. When a cat or dog chews on a Pothos leaf or stem, the calcium oxalate crystals are embedded into the oral mucosa, tongue, and throat. This penetration causes intense pain and inflammation almost instantly. The body's reaction to this physical insult includes a release of inflammatory mediators, leading to swelling and redness. Furthermore, the plant sap may contain other compounds that contribute to the irritation, though the calcium oxalates are the principal agents responsible for the toxic effects.
The symptoms manifest rapidly after ingestion due to the immediate action of the crystals. The most common signs observed in pets include intense oral pain, evidenced by pawing at the mouth, drooling (ptyalism), foaming, and vocalization. Swelling of the lips, tongue, and oral cavity can occur, which may potentially lead to difficulty swallowing (dysphagia) and, in severe cases, compromised breathing if the swelling is significant. Vomiting may also be present, though it is not always immediate. It is important to note that while the symptoms are acute and distressing, they are typically self-limiting and rarely fatal.
Both cats and dogs are susceptible to the effects of insoluble calcium oxalate crystals. However, due to their smaller size and more curious nature, cats may be at a marginally higher risk of taking an investigative bite. The physiological reaction is fundamentally the same in both species. The severity of the reaction can depend on the amount of plant material ingested. A small nibble will likely result in significant oral irritation but may not lead to further systemic issues, while consuming a larger quantity could result in more pronounced gastrointestinal upset, including vomiting.
As a plant, Pothos employs its toxicity as a survival strategy. For pet owners, this means the plant must be treated as a hazard. The most effective strategy is prevention through placement. Keeping Pothos plants in hanging baskets well out of the reach of curious pets or in rooms that animals cannot access is the safest approach. Providing pets with safe, alternative greens like cat grass (Dactylis glomerata) can help deter them from chewing on houseplants. If ingestion is suspected, promptly rinsing the animal's mouth with water or milk can help remove some of the crystals and provide temporary relief before seeking immediate veterinary care.
