Allergic Response to Metabisulftte in Lidocaine Anesthetic Solution

Frequently, patients present to the dental office labeled as “caine” allergic. While allergic reactions to local anesthetics are rarely reported, less than 1% of the adverse reactions to local anesthetics are true immunologic reactions. If, after a thorough medical history, the possibility of an allergic reaction is likely, then skin testing should be performed. A dental cartridge with vasoconstrictor contains metabisulfite as an antioxidant, while a multidose vial of local anesthetic with vasoconstrictor contains both metabisulfite and methyl-paraben as a preservative. A multidose vial of local anesthetic without vasoconstrictor contains only methyl-paraben as a preservative. Therefore, the intradermal testing should include methylparaben, metabisulfite, and local anesthetic solutions. Skin testing allows the clinician to separate autonomic and toxic responses from the true allergic reactions to local anesthetics so those patients are not labeled as caine allergic.
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