Monstera plants, while popular for their lush foliage, contain insoluble calcium oxalate crystals that can be toxic to pets if ingested. Symptoms may include mouth irritation, vomiting, and lethargy. If your pet ingests Monstera plant material, remove it from their mouth, rinse with water, and give milk or a calcium-rich antacid. Monitor your pet and seek veterinary attention if symptoms persist. To prevent toxicity, keep Monstera plants out of reach of pets, supervise them around plants, and train them not to chew on them.