Allergic reactions to local anesthetic formulations.

True allergic reactions to local anesthetics are rare adverse reactions. At the most, they represent less than 1% of all adverse local anesthetic reactions. When true allergic reactions have been confirmed, the reactions are most commonly the type I anaphylactic and type IV delayed hypersensitivity responses. The type I immediate hypersensitivity reactions are the most severe and may be life-threatening. In the event a potential allergic reaction occurs in a dental office, the dentist needs to properly evaluate the events leading up to the reaction and provide a differential diagnosis. A referral should be given to any patient when an allergic reaction cannot be ruled out as an intravascular injection, toxic overdose, psychogenic reaction, or an idiosyncratic event.