There are food allergy tests that you can take, too. I've done the ALCAT test, and it was very helpful. It's a blood test, and provides a big list of red/yellow/green foods.

e.g. Red = likely to cause a strong negative reaction.

I found it to be extremely helpful in finding things that were causing issues.

Kale, Cumin, etc. Things that I would not have easily identified on my own.