Sensitivities and allergies are odd things.
25 years ago, I had a co-worker with fraternal twins, one boy, one girl. Both were lactose intolerant (a sensitivity). Each was fully allergic to other's milk substitute. One drank soy milk, one drank almond milk. Fortunately the cartons included different strong colors, and the household color matched cups, cereal bowls, etc. so accidents didn't happen. It worked for them, but having to stock multiple milks, and to cook with none of them and so on, was tiresome and draining.
I myself am sensitive to galangal. I'm normally okay when it is used to flavor a broth, but more than that, as ginger might be used in a dish, and I am in for some unpleasantness. Oddly, I'm not sensitive to ginger, to which galangal is a closely related. To add insult to injury, I love galangal and a favorite Thai dish is Beef with Galangal and Citrus Leaves, which I allow myself just once every few years and as a solo dining experience, know what will rapidly follow.
Several years ago I read about a theory that the increasing sensitivity to gluten is due to the huge amount of hybridization that occurred in wheat during the 20th century. The wheat humans had been eating and adapted to for thousands of years, has in a few decades doubled or more in genetic complexity. There's lots more there to react to.