No matter how thoroughly yourcat or dog licks the food dish, it’s not clean enough to use again without washing. That goes for water dishes, too. In some homes I’ve seen water dishes with the beginnings of algae colonies forming on the sides and the bottom. Who’d want to drink from that?
Pick up your pet’s food dish after every meal, then wash and scrub with hot water and soap. The water dish should get the same treatment on a daily basis.
Better still, run them through the hottest cycle of the dishwasher to get them really clean and sterilized. Stainless steel or heavy plastic “crock-style” dishes are best for frequent cleaning: They last forever and stand up well to the abuse a pet can dish out. I have seen stainless steel pet dishes that still look pristine after more than two decades of use. That’s good news for everyone!