title: Lidocaine Allergy: Do Positive Patch Results Restrict Future Use?
abstract: BACKGROUND
  Adverse reactions from lidocaine are commonly reported. When allergy is suspected, patients may be referred for specific skin testing to confirm the association of their clinical findings.
  
  
  OBJECTIVE
  We aimed to investigate 13 cases of suspected lidocaine allergy to analyze if positive patch results restricted future use as an injectable local anesthetic.
  
  
  METHODS
  A prospective study was conducted from March 2013 to September 2014 at 2 academic hospital-based patch test clinics in Toronto. Patients were tested to the North American Contact Dermatitis Group standard series (Smart Practice, Phoenix, AZ) and, if suspicion for lidocaine allergy was high, a local anesthetic series (Chemotechnique Diagnostics, Malmö, Sweden) was added. Intradermal skin testing to local anesthetics below irritant concentrations was subsequently conducted in lidocaine-positive patients. If negative, a subcutaneous challenge with 1% lidocaine was done.
  
  
  RESULTS
  Thirteen of 756 patients patch tested were positive to lidocaine. Seven patients had relevant reactions to over-the-counter products containing lidocaine, 2 reacted to subcutaneous lidocaine, and 4 had incidental findings. There were no patients with positive results to intradermal testing. Three patients had delayed reactions to the subcutaneous challenge.
  
  
  CONCLUSIONS
  Patients with positive patch tests to lidocaine and negative results to intradermal testing and subcutaneous challenge may be safe to use lidocaine as an injectable local anesthetic in the future.
authors.affiliation: From the *Division of Dermatology, Department of Medicine, Sunnybrook Health Sciences Centre; †Division of Clinical Immunology and Pharmacology, Department of Medicine, University of Toronto; and ‡Department of Occupational and Environmental Health, St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Michael Domenic
authors.initials: MD
authors.lastname: Corbo
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Weber
authors.forename: Joel
authors.initials: J
authors.lastname: DeKoven
mesh_terms: D000779:Anesthetics, Local / Q000009:adverse effects*; D004342:Drug Hypersensitivity / Q000175:diagnosis* / Q000209:etiology; D006801:Humans; D007428:Intradermal Tests; D008012:Lidocaine / Q000009:adverse effects*; D010328:Patch Tests; D011446:Prospective Studies
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine