Real Christmas trees can be harmful to cats if they are not properly cared for. Cats are curious creatures and may be tempted to climb the tree or chew on its branches, which can cause injury or damage. Additionally, the tree may contain sharp needles or decorations that could cause harm if ingested. To ensure the safety of your cat, it's best to secure the tree firmly in place and keep it away from areas where the cat has easy access. If you notice your cat showing any signs of distress or illness, seek veterinary care immediately.