Pinpoint #515

The Solution is: Things that people are allergic to

The category "Things that people are allergic to" unites all five clues through a shared association. Each clue connects differently: Cats → Cat allergy (dander/saliva proteins), Nuts → Peanut/tree nut allergy, Eggs → Egg allergy (egg whites), Pollen → Seasonal pollen allergy. The abstract nature of the connection means more clues are typically needed before the category becomes apparent.