How to tell what are the signs of an allergic reaction to novocaine?

See Allergy: Local anesthetic allergy is very rare, some argue that it does not even exist. If there is a concern about a reaction to a local anesthetic agent see and allergist. They will review your history, perform a physical and if needed they can skin test to the local anesthetic if needed. Based upon those results decision can be made about if one is allergic and how to proceed.