I've become overly cautious about sharing food recently (just a mild way of saying I'm paranoid about it), as I have a severe nut allergy, and most of the people wanting my food or handling it of their own accord are 7-10 year olds who also love peanut butter.
While I'm sure most of the time I'd be perfectly fine eating a bag of chips after they've taken a few handfuls, it's just never worth it to me. Same with foods that are stamped with "may contain nuts". Sure, that cookie might be absolutely stellar, but it's never ever going to be worth my life on the off chance it actually has come into contact with some pecans.
I feel like crap about it though. They're always offering me treats, or trying to share their own food and I have to consistently turn it down; only for me to later snap at them when they try to take a handful of pretzels without asking. I really don't mind pouring you a bowl, but please don't just reach in there, it worries me. :/
So yeah... same with people not washing their hands. I know you're not intentionally dirty, but I don't know what could have been on that doorhandle you touched. I never eat anything unless I've washed my hands first, so do the same and we're golden.
(Anyone else around here have an extremely severe food allergy? Am I being ridiculously overcautious here?)