Citrus oil is toxic to cat. Poisoning can occur through ingestion as well as through high levels of skin contact. Cats that have come into contact with citrus oils will have a strong citrus smell to their skin. Affected animals may drool excessively. They may also appear weak and listless or appear depressed, and may not be able to stand. Hypothermia is another common sign, meaning that your pet may feel colder to the touch than usual.