Are poinsettias poisonous to pets

Yes, poinsettia plants are harmful to cats.

Specifically, poinsettia contains a milky sap which is called latex (even though it is not the latex which helps in rubber production). Latex irritates a cat's digestive tract. Cats that eat poinsetta for Christmas will need to be treated for irritated mouths and stomachs as well as for nausea and vomiting.