Evaluating a dental patient for local anesthesia allergy.

The determination of particular allergens with respect to local anesthetics may present difficulty within the realm of clinical dentistry. A case is presented that dramatizes the difficulties in determining the specific allergen after a patient undergoing several episodes of restorative dentistry with several varying regimens of local anesthesia repeatedly reacted with skin rashes and pruritus approximately 36 hours after treatment. The patient was a 76-year-old man with a complex medical history. A challenge procedure performed with a commercial formulation of local anesthesia resulted in a positive delayed hypersensitivity reaction. An additional challenge procedure with cardiac lidocaine resulted in a negative challenge. A latex-induced delayed-type hypersensitivity reaction was suspected but unproven because the patient declined further allergy testing. Therefore, the conclusion was that the allergen was an unknown substance within the commercial local anesthetic formulation.