My understanding is that our understanding of the delayed type allergies are still very limited. And there is no clear medical test for it. Even gluten sensitivity that is not celiac doesn’t have a test. Unfortunately when there is no test and no medication for something it seems it almost doesn’t exist to the medical community. This is where western medicine falls short. It is superb at acute crisis management and I owe my life multiple times to it. But it has a blind spot to viewing people as a whole system and to the management of chronic ills, chronic fatigue syndrome is one that comes to mind. I suspect we are just starting to understand all the biochemistry that underlies many mysterious chronic illnesses.