It's incredible that people think that kids can't be taught how to work cleanly...My kids know that you don't lick anything when you're working with food, and they seem to do fine. My mother was making gingerbread houses with them once, and she was telling them that they could eat the candy while they were working on the houses. Of course, there I am, mean mom saying "no, don't eat anything while you're working" and she replied "oh, but they can't help it." I told her yes they can, they do all the time unless someone's sitting there encouraging them to do it!
And for anyone who thinks I'm too mean for making them wait to eat anything, they're definitely not sugar-deprived! They eat Puh-Lenty of candy, believe me!
They just know that you shouldn't put your hands up around your mouth while you're working with food.
I was teaching a cake decorating class to a bunch of 9-yr-old girls once, and the first class all they wanted to do was suck the icing out of the bags. I spent the whole time freaking out about sanitation, but they wouldn't listen to me, and they insisted that they COULDN'T HELP THEMSELVES!!! For the next week's class, I mixed an entire container of salt into the practice icing, then told them to go ahead and try it. Amazingly, none of them licked anything that day!
I pointed out to them at the end of the class that they had done really well with not licking anything, and that it proved that they definitely COULD help themselves if they wanted to!