So i'm using allegra (fexofenadine) allergy pills, and i'm going to a party where there will be some alcohol, what can happen if i drink?

Little interaction: Allegra does not cross from the bloodstream into the brain so it does not cause sedation or other behavioral side-effects. It's an excellent choice as an antihistamine if you plan to consume alcohol. Claritin rarely causes sedation, zyrtec sometimes (~10%) and Benadryl (diphenhydramine) often (25-50%) - so don't mix these with alcohol. I know that because you asked you are planning to drink responsibly.