eli5: Allergies. Why did we as a species develop allergic reactions to certain foods, chemicals ext.?

Question

I just don’t get why our bodies would reject nourishment or have a bad “reaction” to something as simple as grass.

In: 2

Answer 1

Ya, why am I allergic to pollen? It’s so bad I feel like nature is trying to burn my eyes out for 2-3 months of the year.