This is similar to what I experienced at my naturopath. They drew blood and were able to tell me I was sensitive to gluten!
I used to be really good at science and would've been able to explain different types of antibodies - unfortunately now a lot of my biology knowledge has escaped my brain! But I'll give a simplified overview the way I understand it. There are different types of antibodies which cause allergic reactions. The "igE" antibody is the one that instantly causes you to wheeze, swell up, itch, need a trip to the ER, etc. Those are the obvious allergies! The allergies I am having to food are the "delayed reaction" kind. igA or igG. Those allergic reactions are more subtle and can happen DAYS after the food is ingested. So you may have a general feeling of being unwell but not know why. That's why they do the blood tests - it's the only way to really know!
I don't have Celiac Disease, or maybe I just have the mild form of it. I DO have SENSITIVITY to gluten, which in my opinion would probably turn into something worse down the road! So, I'm glad I caught it relatively early so hopefully my body can heal.
It really stinks around the holidays because everyone around me is eating crap; I know they are not doing their bodies any favors but I have to just shut up and observe. Then after the parties they are sitting around groaning about feeling sick, "stuffed" and sleepy. While I feel just fine. But it does suck to not be able to enjoy the things they try to share with me.