Good question.
I wasn't around 30 years ago, but here are some of my guesses:
1) the internet makes it much easier to hear about stuff that happened all the time previously but nobody really heard about it
2) increasing population = increasing number of people with allergies
3) we eat a lot of genetically modified or chemically treated crap and might not understand potential hereditary/long term effects
sorry for any poor wording. i'm not feeling very well right now and am not thinking as clearly as i should be
Sorry you're not feeling well. Hope you get better soon.
I think your guess #1 hits close. These allergies may have always been around, but fewer people were aware of them.
My own 2¢: Clean water supply, widely available antibiotics, and public immunization have made dangers from life threatening infectious diseases, such as polio, fade away. As a result, our fears get replaced by new, previously unnoticed health dangers.
Today cancer is a big source of fear and loathing. In a world where people didn't live to their 70s and beyond because they died of diptheria, measles, or tuberculosis, who worried about cancer?
I remember a bunch of kids in school allergic to PB and bee stings... We used to be able to bring PB to school but my kids can not bring it...
Thirty or forty years ago, schools weren't scared to death of parents who filed law suits. They ban peanut butter sandwiches only because they're scared of the liability costs.