system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do so many people have peanut allergies?

Just saw on the news that a trial was happening in NZ which could lead on to a cure for peanut allergies, and it made me realise that many people around the world all have this common allergy. I guess my question is, why is it so common? It's interesting enough to know that it is widespread, but knowing why would help me make sense of it all. ELI5.
gpt
Nobody's sure. It's more common in developed countries which has led to the ***hygiene hypothesis***, which is basically that our immune systems like to pick fights, and will attack random substances if they can't find real infections - even if they're delicious and harmless like peanuts.