In certain situations, dish soap can be used on your cat. However, it is not something that you should use on a regular basis. Dish soap is useful in removing fleas, skunk spray, and oil-based substances, but since it has a very drying effect, it is something that should be reserved for emergencies only rather than washing on a regular basis. If you are going to use it, you should choose one that is very gentle. For regular washing though, you should really stick to specially formulated shampoos for cats.