Is it possible that acetaminophen allergy makes my pain worse?

Unlikely: Allergic reactions to Acetaminophen (apap) occur in less than 1% of cases and symptoms are typical for allergic reaction, such as causing itchy, red rash/hives or anaphylaxis (allergic reaction affecting several organ systems). Pain in abdomen or extremity can be caused by apap in 1-10% of users, mechanism unknown. More likely, pain increase in area being treated is due to lack of effect by apap.