Adverse responses to local anaesthetics.

Progressive challenge was used to investigate twenty-seven patients with a history of an adverse response to local anaesthesia. True allergy was detected in only one patient. The method does not exclude reactions to additives and preservatives in local anaesthetics. If preservative-free local anaesthetics are used for subsequent exposure in patients with no response to progressive challenge, subsequent exposure is safe. The possibility that some of these patients may be reacting to preservatives in the solutions cannot be excluded by such testing. Where possible preservative-free local anaesthetic preparations should be used for subsequent anaesthesia.