How to tell why i always have nasal allergies the day after i drink beer?

Hard to say: Alcohol has histamine releasing properties, and following drinking some people may have congestion. This is not really allergy. However some people may have true allergy to components of any beverage, whether beer or anything else, and develop allergic responses. I would avoid exposure to it, or talk to your doctor about a referral to an allergist. If you have trouble not drinking beer, get help.