Before modern hygiene and housing standards, children died in droves of infections in the West. Now few do, but instead they are increasingly bothered by allergies, which are immune-system malfunctions. The current view among researchers is that there is a connection here. Live in dirt, and you will get infections that may kill you, but you won’t get allergies.
The Skeptikerpodden podcast has an interesting interview with bacteriologist Agnes Wold that touches upon about this issue. It made me wonder.
The kids who get allergies today: are they the ones who would have survived 200 years ago, or are they the ones who would have died? Or would there be no strong correlation between the outcomes if it could be tested?