Live Christmas trees are considered to be mildly toxic to pets. Fir tree oil can irritate to the mouth and stomach, causing excessive drooling or vomiting for your pet. Tree needles are not easily digested, either, and can possibly lead to GI irritation, vomiting, or obstruct the gastro tract of your animal. Pine needles can also be ingested and puncture intestines, and pine is highly toxic to cats, potentially causing liver damage and death.
Artificial trees can also be dangerous when eaten—the toxins from the artificial material and intestinal obstruction being the main concerns. When you are decorating for the holidays, don’t forget to keep other pet-poisonous plants, such as Mistletoe and Holly, out of reach from your furry friend.
Also note that many times pets likely won’t consume mass quantities of tree material—meaning it’s not enough to make them sick. However, still continue to monitor them for any changes of behavior excessive licking, salivating, appetite, activity, water consumption, vomiting and diarrhea. And call your vet right away if anything seems wrong.