With the number of changes in farming and GMO products, production soil, other effects of industrial farming, etc, etc, it's not surprising. More diversity in marriage and resulting younger generations can also change/increase allergy profiles as well, since you may now have reactions to things that effect either parent or to a greater extent.

It's complicated, to say the least. Also, you can go most of your life with smaller reactions to something before it starts to get bad. (Discovered legume allergy at 40yo)