Immediate-type allergic reactions to local anesthetics

Adverse reactions to local anesthetics are frequently reported, but true allergic reactions are very rare.1,2 Adverse reactions are commonly related to vasovagal reactions, dose-related toxic effects, and the side effects of epinephrine within local anesthetics.3 Usually, skin prick tests and intradermal tests of potential causative agents are performed to diagnose allergies. Evaluations of allergic reactions to local anesthetics based on such skin tests have been reported previously.1,2 Recently, the number of drugs containing local anesthetics, including over-the-counter medicines, has increased. Therefore, the number of individuals that have become sensitized to local anesthetics might have increased. However, there are few recent reports about allergic reactions to local anesthetics. Thus, we investigated our recent results of skin test reactions to local anesthetics. We conducted a retrospective study of the cases of 67 patients (16 males, 51 females; median age: 51 years; range: 19e90 years) who suffered adverse reactions to local anesthetics and underwent skin tests between January 2008 and December 2015 at the Department of Dermatology, University Hospital, Kyoto Prefectural University of Medicine. The study protocol was approved by the university ethics committee and was conducted in accordance with the Declaration of Helsinki. The skin tests of local anesthetics included skin prick tests, intradermal tests, and subcutaneous challenge tests. The skin prick tests were performedwith 1:1000,1:100, and 1:10 diluted solutions and undiluted solution, together with positive (histamine dihydrochloride; 10 mg/ml; Wako Pure Chemical Industries, Osaka, Japan) and negative (saline) controls. Wheals weremeasured at 15min after the application of the test solution. A positive response was recorded when the mean wheal diameter was more than half of that of the positive control. Intradermal tests were carried out with 1:1000, 1:100, and 1:10 diluted solutions and undiluted solution (0.02 ml), together with a negative (saline) control. The sizes of areas of redness and wheals were measured at 15 min after the injection. A positive response was recorded when the mean wheal diameter was 9 mm or the mean area of redness was 20 mm. Following the intradermal tests, subcutaneous challenge tests were conducted. Undiluted local anesthetic (from 0.1 to 1.0 ml) was injected below the lateral surfaces of the patients' arms. The local findings observed around the injection site and the subjects' general symptoms and vital signs were examined after 30 min. The majority of reactions occurred during dental procedures (n 1⁄4 47), followed by minor surgical procedures (n 1⁄4 10), mucosal