There are two more factors in play here, that cannot be ignored:
3) Better testing, reporting and ultimately awareness of allergies. That funny feeling you get on your tongue from eating an apple isn't normal. It's a very mild allergy. If eating peanuts make you a little nauseous, that's probably also a mild allergy. Of course, knowing that it's an allergy, you truthfully answer "yes" when an airline asks about the allergy, because you'd rather have a different snack, and that leads to...
4) Utter overreaction, because it's "better safe than sorry". Somebody on a plane says they have "a peanut allergy", and rather than put effort into identifying where that passenger is sitting and how severe their allergy is, the entire plane must be treated differently because the allergy might be severe.
Unfortunately, thanks to those two factors, the impact of allergic reactions is greatly increased, as well. There's still only a small handful of kids at a school who are allergic to peanuts, and maybe one is severe enough that he needs to be careful what he touches, but now every parent knows that, thanks to allergies, they have to pack something else as the quick-and-easy lunch. Every informed citizen knows that schools are increasingly restricting lunch options due to allergies, and everybody has a friend or coworker who has some weird allergy. The obvious conclusion is that allergies are becoming more predominant.
After that realization, humans do what humans do best: we rationalize. We may think humans are evolving to be weaker, due to advancing technology reducing the pressure to have a strong immune system. We may blame modern medicine, finding tenuous links between medicines/vaccines and allergies. We may criticize overbearing parents for minimizing their child's exposure, beyond what links have been shown. We may simply gloat over our allergy-free life.
There are several factors and mechanisms at work, but the bottom line is that perceptual changes are outpacing biological ones. That's often a recipe for knee-jerk politics.