The allergic reaction is to alcohol, not a season allergy or something that Allegra will relieve. The theory is that once an alcoholic metabolizes alcohol that the body craves more of the same where as a "normal" person would usually get a slightly out-of-control nauseous feeling and believe that they have had enough. This reaction, therefore, causing the alcoholic to drink to excess at the point of consumption. Which is why the first drink is too many and then a thousand is never enough (sorry I don't like to use slogans/sayings, but it fits here).