Yes, eating styrofoam is not good for your kitty. If he or she eats enough of it an obstruction can form which will need to be surgically removed. Plus, some styrofoam is treated with chemicals that help it dissolve and breakdown faster, which can be toxic to your kitty. Keep all styrofoam far away from your cats and have them seen by a vet immediately if they stop eating, vomit or have a painful belly after ingestion. Please let me know if I can be of further assistance. If this has been helpful, please hit the green accept button. Good luck!