I suffer from the same problem! I'm 49, been this way since a kid, I thought it was from growing up in a family with disgusting eating habits, and I generally did NOT get along with them.
But, I did see something on TV about it being a form of OCD. I have been living with my elderly mother and think I will just about lose my mind if I hear her "smack" her mouth ONE MORE TIME !!! (let alone eat around her) I want to move out but will feel guilty leaving her alone.
I have earplugs, but she gets offended. I am buying some clear ones I saw at a drug store, maybe she won't notice.
My kids eat just like their dad, and when we were together, I'd wait to see what room he was eating in, and go in the opposite direction. Now that they are adults, thank God, we don't eat together that often.
I've OFTEN said something to people in a store, smacking their gum, especially if they are working! It's a terrible way to live...being hyper-sensitive to disgusting people. God help me. (and those of you with the same "problem". thanks for letting me get this off my chest!