eli5: How can you eat something you’re entire life and then suddenly become allergic to that food / food type overnight?

Question

eli5: How can you eat something you’re entire life and then suddenly become allergic to that food / food type overnight?

In: Biology

Answer 1

This is due to many factors. For example, grain today contains more gluten than in the past. Or: we get older and the immune system changes. Or: an intestinal disease changes the intestinal flora.