Food is such a huge part of social encounters/ functions, and the culture in general.
Food is possibly the primary (at least secondary?) pleasure of travel.
People can get really religious about food choices, whether for or against.
When you really can’t eat something due to allergies or autoimmune disorders and the like you may become envious of those diets done more for moral reasons or even as a lifestyle choice. At least it won’t kill you acutely or slowly if you let it slip!
You will be met with a lot of skepticism.
Those who don’t have food issues or are not aware can get really high and mighty and all scientific on you about placebo effect and double blind studies.
There are still a lot of holes in our mainstream knowledge about allergies. Even some doctors.