Try using a Neti pot to help clear your nasal passages where the allergen could be hiding.
Rinsing out your nasal passages is a good way to keep allergies at bay. Also be sure to wash your hands after coming inside the house because allergens can be on your hands then could be passed to your nose when you touch your face.
If something is in the air that affects your allergies you'll also need to shut out those allergens by closing the windows even on a nice day.
Get an air purifier which should also help with the allergens.