You try avoiding anything that has onion, garlic, chives, shallots, leeks, etc.

"A pickle" is an onion (in their parlance)
Pickle is Branston or Picalili
Caesar salad is idiotform for Caesar salad dressing and they don't know what that is just that they like it so "wots the problem, do you have an alergy?" "NO, my wallet does!" followed by a puzzled look.

And why does BLT have to have mustard? That is a BLTM surely?

Oh the travails of a supertaster.........

Ever tasted Meat? (reference the Horsemeat/Lasagna scandal in the UK) Those masks are there to hide the truth about ingredients, don'tyaknow.