Use of diphenhydramine for local anesthesia in "caine"-sensitive patients

Emergency physicians regularly encounter patients who require local or topical anesthesia in the course of their emergency department (ED) treatment for lacerations, abrasions, or mucosal surface pain. Rarely, patients disclose a history of allergy to lidocaine and its chemical analogues, and the physician is faced with the problem of achieving adequate anesthesia without the use of these drugs. Research studies and anecdotal reports have suggested that diphenhydramine hydrochloride (Benadryl) may be useful as a substitute. We describe three cases of patients with histories of "caine" allergy who required local anesthesia for laceration repair. Infiltration with a 1% diphenhydramine solution provided adequate anesthesia without noticeable adverse effects. We feel that diphenhydramine has a place in emergency medicine practice as a second-line local anesthetic agent.