So this is not exactly true. There was a scientific study done in which they had a divided a group of babies who had eczema (and were thus prone to peanut allergies) into a two groups. One group was exposed to peanuts during early development while the other half were not. There were significantly more peanut allergies (and more severe allergies) in the group who was not exposed to peanuts. In other words, by trying to protect our kids from allergens, we've made them more susceptible.
Additionally, there has been a recent uptake in the number hospitalizations due to self-harm. This points to an actual increase in mental illness as opposed to just an increase in understanding of mental illness (although one could try to argue that we are better at getting the children to the hospital). I believe there's a pretty good case that social media and the internet has played a major role in modern rates of recorded mental illness.
The source for both of these theories and the data behind them are The Coddling of the American Mind by Greg Lukianoff and Jonathan Haidt.

On one hand the scientist in me screams [citation needed] despite actually giving a potential source on claims. On the other hand, I can feel that might be right because I never ever heard of anyone, even on the Internet, from where I live, being allergic to nuts, given how we eat that shit all the time and the most popular type of cheap candy is basically a bunch of peanuts encased in sugar. (and ironically peanut butter is super expensive, wanna show your clout? Prove you can afford to use Nutella regularly)

Kinda curious about other allergies though, my sister loved pineapples but at some point she developed a rather killer allergy to it, just touching a whole pineapple barehanded is enough to make her skin break in hives, and did met a few people who developed gluten intolerance allegedly "from overdoing it" (their words).