Cats should not eat oranges because oranges are acidic fruits. Giving them to cats will irritate their stomachs and intestines, causing symptoms such as vomiting and diarrhea. Most cats dislike the smell of acidic fruits like oranges and will run away as soon as they smell them. 
Furthermore, the essential oils and citric acid in oranges are toxic to cats. Citric acid can irritate the stomach, while the essential oils can cause central nervous system problems, as well as gastrointestinal discomfort, leading to symptoms such as vomiting and diarrhea. Long-term exposure or consumption can cause indigestion and even death in cats.
The smell of oranges can irritate a cat's respiratory tract and cause it to sneeze, especially when peeling an orange, where cats will be particularly sensitive.
