Cats must not eat mustard. Mustard is a very irritating food for cats. Eating it will damage the taste system and gastrointestinal digestive system. Eating a large amount of mustard can cause symptoms such as foaming at the mouth, vomiting, and diarrhea. Owners should be careful not to feed their cats any spicy food at home.

If you keep a cat, you must be responsible for it. You cannot use a cat to "test poison" just because you want to see its reaction. Cats’ gastrointestinal tracts are different from those of humans, and there are many taboos for cats in human food.