Dish soap can kill some adult fleas, but it is not safe for your pet’s skin because it can remove the natural oils, making it more prone to infection—especially if there is already irritation from fleas. Dish detergent is also not effective since it kills only adult fleas. Some eggs will wash off during a bath, but this will not address the majority of flea eggs in your home, and you should never bathe your dog with dish soap.