Well as we're going to be going to this here March MudGather at WYSIWYG's, I guess I'll offer my 2 cents. (12 cents?)
IMO there's no point trying to avoid all allergens. As shown by the above lists, you would be pretty much left with water. What we do at the Getaway is ask people to let us know regarding allergies and other food restrictions, and try to have ONE dish they can eat at each meal.
I don't seem to be allergic to corn but am allergic or intolerant of corn syrup, and certain other sweeteners. Also sorbitol and maltitol (ugh!). At home, I keep my own bottle of organic ketchup since Heinz switched from sugar to corn syrup.
Also, because of transplant risk factors, I have to be sparing with saturated fat, salt and sugar. These restrictions aren't life threatening, in the short term at least. Still I frequently have to stop eating something because it's notably fatty and salty, or because a sweetener in it is making my skin burn and my chest ache.
As Carol says, prepared dressings and mixes are almost always a problem in these areas. Sure played hell with my own cooking BTW -- prior to all these restrictions I thought Soy sauce and salad dressings made up one of the four basic food groups. (Chicken basted with Kraft Zesty Italian dressing -- yum.)
However -- people don't need to cook to my requirements. (For one thing, I cheat on my diet a bit, a moderate amount of fat and salt won't stop me.... ) We'll bring potluck, and I will probably also bring lots of salad and fruit, maybe some cheese. Also, when I travel I take a CARE package - low salt Triscuits, Jif peanut butter (no corn syrup), some high protein bars, nuts, whatever. I don't want people to drive themselves nuts trying to fix food for me. I'd rather they fixed whatever is easy and fun, and I can have cheese and salad or whatever if it doesn't work for me.
I may not even be able to eat my own potluck! I made a really tasty meat pie this week and then couldn't eat it. I still don't know where the problem was but it made my chest ache and my skin burn. Sigh.... Bill sure enjoyed it though, he got to eat almost a whole meat pie although not at one sitting. :-D