And that's the good news. Research on manual dish washing done at Ohio State University shows that food left on dishes after washing can harbor bacteria. But lipstick left on glasses seemed to have "antimicrobial properties."
Some other findings for your dining pleasure:
Fork prongs are especially dangerous because they can protect old food particles and thus bacteria.
Dried milk in glasses grew the most bacteria. But they don't understand why milk sticks to glass so successfully.
Wash dishes before the food dries.
The purpose of the research was to test restaurant dish-washing procedures as unclean utensils or dishes can lead to food poisoning. One final finding: scalding hot water was not as crucial as soaking the dishes in ammonia-based sanitizers after they were washed.