You might find this article (especially the comments) informative. You want to be reading Art Ayers’ comments (he’s the author). He talks repeatedly about gradually adapting your gut flora to foods you can’t tolerate. If you avoid them completely, the bacteria needed to digest them die off, and the intolerance becomes more severe. If you eat too much too soon, there isn’t enough bacteria to digest it completely, and symptoms result. In the case of lactose intolerance, probiotic bacteria are able to exchange lactose digestion genes with indigenous bacteria, resulting in lactose tolerance.
When I tried introducing Greek yoghurt, I got some bad symptoms, but I was eating way too much way too soon after avoiding all dairy for over 6-weeks. It’s much more likely that lack of relevant bacteria was the problem, and not some sort of immune response. True allergies are rare, gut flora issues aren’t. I’ve decided to test this theory by starting dairy kefir at maybe 1-2 tbsp per day until I can tolerate it. Here’s a post from the comments I linked above.
after probably over a month or so with kefir, sauerkraurt, pickles, goat yogurt, cider vinegar, cultured butter(may be others i cant remember)
I CAN EAT CHEESE!!!!!!! i digested smooth sailing raw goat feta and cheddar 🙂 happy girl. so much easier to rack in my calories with cheese