Los anestesicos locales se administran ampliamente, son seguros, efectivos, capaces de aliviar el dolor, de hacer posibles los procedimientos quirurgicos y tienen minimo riesgo de toxicidad. Verdaderas alergias a los anestesicos locales son raras. La mayoria se relacionan con los esteres. Son el resultado del metabolismo de los esteres a acido para-aminobenzoico (PABA). Alergias a las amidas son raras. Algunos casos se han relacionado con el metilparabeno, el cual es un preservativo de la lidocaina. Este reporte muestra un caso de alergia a las amidas, relacionado con el metilparabeno. ABSTRACT Administration of local anesthetic solutions have been widely used in dentistry as safe, effective drugs which relieve pain and enhance surgical procedures with a minimal risk of toxicity to the patient. True allergies to local anesthetics are rare, with most of them being associated the metabolism of ester agents into para-amino benzoic acid (PABA). Allergies to amide agents are also very uncommon, although a few reported cases have been related to methylparaben, which is an added preservative to a multidose vial of lidocaine. This article presents a case report of patients with allergy to amide local anesthetic related to methylparaben.