Elimination diets can also be used for allergy symptons, behavior issues and other things. You can eliminate lots of foods and add them back in one at a time, or eliminate one thing at a time and see what happens.

I have periodic bouts of IBS but fortunately for me it's been very easy to identify the culprits, most of the time. I quit eating fast food of any sort, period. Also, anything that is heavy on cooked tomatoes (which are very acrid) , or a tomato cheese combination, are off the plate permanently, like lasagne, or more than one slice of pizza. I know for some people it can take a lot of trial and error to find the culprits. One of my best friends has a lot of triggers, and she was very helpful in pointing me in the right direction. There's a lot of good info out in internet land with likely trigger food lists and so on.