What's common to pie crusts and deep fried battered foods? [closed]

A member of my family gets migraines when he consumes certain foods. I'm trying to nail down which component of these foods is the trigger. What do pie crusts and deep fried battered foods (eg onion rings, fish and chips) have in common?

It's really puzzling me since there are so many similar foods that don't cause migraines for him, such as other fried foods (whether in oil or in butter) and other baked goods. And to make matters even more confusing, not all pie crusts and battered fried foods trigger him. I've looked through some lists of common dietary migraine triggers and none of them seem to fit. Gluten seems to be fine for him.

I made an all-butter pie crust tonight (just flour, butter, salt, and water) to see if it went over better than store bought crust, but alas, it triggered a migraine. I'm going to try making an all shortening one next.

What could be a common denominator in these foods? Any thoughts on this would be appreciated!