I learned that some people are allergic to benzocaine or procaine because they metabolise into PABA. But I also heard that parabens in topical creams and even in lidocaine vials can cause reactions. Are ester local anaesthetic allergies and paraben allergies related? And do they cross-react?
Understanding allergies to local anaesthetics can be surprisingly tricky. Patients can report being “allergic to all anaesthetics,” but the real culprit is frequently something far more specific, such as PABA from ester-type local anaesthetics or parabens used as preservatives. These substances share some structural features, but they behave very differently in the body. Because of this, you may hear mixed messages about cross-reactivity, preservative-free formulations, and whether lidocaine is truly “safe” in someone with a benzocaine allergy.