What part of a plant causes allergies?

yes but depending on the plant the stem and leaves can cause contact allergy too

Yeah it's Pollen because it can produce sneeze in the environment

what i'm talking about is that there are medicine allergies and food allergies too,besides seasonal allergies 🤧

I know what you mean, Did you try Flonase Nasal Spray. That's just 1 type of allergies.