[Immediate reactions to local anesthetics: diagnostic and therapeutic procedures].

Background: Despite the widespread use of local anesthetics and frequently reported adverse reactions, true IgE-mediated allergy to local anesthetics is extremely rare. We report on 80 patients seen in our department for adverse reactions to local anesthetics, and we propose a clinical strategy to confirm or rule out immediate allergy to local anesthetics.

Patients And Methods: We retrospectively analyzed the medical files of all patients referred to our department by their doctor or dentist for suspected immediate allergic reaction to local anesthetics between September 2001 and May 2004. These patients underwent skin tests (prick test and intradermal tests) exploring immediate allergy.

Results: Eighty cases were tested in our department during this period. The most common symptoms were facial edema or dizziness following injection of an anesthetic occurring between a few seconds and more than 48 hours after administration. The causative local anesthetics were of the amide group in 91% of cases and of the ester group in 9% of cases. Seventy-nine patients had negative skin tests, allowing us to eliminate the diagnosis of immediate allergy, and the anesthetic could be reinjected with good tolerability. One patient presented with positive skin tests to lidocaine and cross reactivity to mepivacaine.

Comments: Adverse reactions to local anesthetics are common and are mostly of pharmacological or toxic origin. However, allergic accidents with local anesthetics are rare and are mostly of type IV involving specific T cells. Immediate allergy to local anesthetics remains extremely rare with less than 10 authentic documented cases being published to date. Skin tests offer a reliable method for exploring immediate allergy in our experience and we propose a diagnostic strategy to confirm or rule out immediate allergy to local anesthetics.