I have certain things I would rather avoid, but i won't list them. In my own mind they are 'unsafe foods'. Rationally, I know they are safe as my girlfriend and family eat all the things that I have issues with, all the time. And they have NEVER been ill. But i still can't eat them!
Best thing to do if ou have ever been ill after a specific food is to go bit by bit. Have small amount of it a month later and then a bit more a week or so after that until your mind learns that it is safe again.
A lot of non-emets have certain alcohol spirit avoidances i.e. something they drank way too much of as a teenager, which made them ill. And now they cant touch it. It's all mind over matter and just hearing the name of the drink can make them nauseous!