I have many food allergies and what you describe is the reaction I get, sometimes followed by a migraine. I was allergic to beef and didn't eat any for years and have slowly introduced it back into my diet. I have noticed that I have been eating too much of it and I am starting to have the same old reaction to it. I guess I couldn't be happy with just a little bit of beef once a month or so.
I am also allergic to corn and had not had popcorn in a number of years and bought some microwave popcorn recently, still can't handle that. I gave the rest of the box to my daughter. It was that or throw it away, because it was so good. I never thought I could get used to going to a movie with out popcorn, but I did.
I have had allergies for years, but had the RAST test when I was tested for the food allergies about 15 years ago. This type of test is more expensive than the skin test and is done through blood work. It was certainly helpful for me.
You could probably try process of elimination of certain foods, especially if you have UC, you don't need to upset your system any more than necessary. Have you talked to your doctor about the possibility of food allergies?