Unfortunately, Christmas trees can be toxic to cats if they chew on or ingest the needles or sap. Some of the symptoms of poisoning include vomiting, diarrhea, drooling, lethargy, and difficulty breathing. If you suspect that your cat has ingested any part of the tree, it's important to seek veterinary care immediately. In addition, it's a good idea to keep your cat away from the tree and to monitor them closely for any signs of illness or abnormal behavior.