Alcohol intolerance can cause immediate, unpleasant reactions after you consume alcohol. The most common signs and symptoms of alcohol intolerance are nasal congestion and skin flushing. This condition is sometimes inaccurately referred to as an alcohol allergy. Alcohol intolerance is caused by a genetic condition in which the body is unable to break down alcohol. The only way to prevent alcohol intolerance is to avoid alcohol altogether.
In some cases, what may seem to be alcohol intolerance is caused by a reaction to something else in an alcoholic beverage — such as chemicals, grains or preservatives. In other cases, reactions are caused by combining alcohol with certain medications. In rare instances, reactions to alcohol can be a sign of a serious underlying health problem that requires diagnosis and treatment.