title: Lack of penicillin resensitization in patients with a history of penicillin allergy after receiving repeated penicillin courses.
abstract: BACKGROUND
  Up to 10% of the population reports an allergy to penicillin, yet more than 80% of these individuals lack penicillin-specific IgE antibodies. A negative result on a penicillin skin test is highly accurate in identifying who can safely receive the antibiotic at the time of testing. However, its negative predictive value for future courses is unknown because it is uncertain whether patients with a history of penicillin allergy are at risk of becoming resensitized.
  
  
  OBJECTIVE
  To determine the rate of penicillin resensitization in adult patients with a history of penicillin allergy after they are challenged with repeated courses of oral penicillin.
  
  
  METHODS
  Adult patients with a history of penicillin allergy consistent with an IgE-mediated mechanism were recruited and underwent penicillin skin testing. Those with negative skin test results were challenged with 3 successive 10-day courses of penicillin V potassium (250 mg by mouth 3 times a day), providing their penicillin skin test results remained negative prior to each course. Patients with positive skin test results were not challenged.
  
  
  RESULTS
  Of 53 patients with initially negative skin test results, 46 completed the protocol, and each tolerated all 3 courses of penicillin with negative skin test results throughout. No patients had a converted skin test result from negative to a positive, yielding a resensitization rate of 0% (upper 95% confidence interval, 2.1%).
  
  
  CONCLUSIONS
  Adult patients with a history of penicillin allergy are not at increased risk of resensitization after receiving 3 courses of oral penicillin. Because a negative penicillin skin test result is predictive for subsequent oral administrations beyond the time of testing, adult patients with a history of penicillin allergy can be skin tested electively, which may avoid unnecessary treatment with alternate broad-spectrum antibiotics.
authors.affiliation: The Corvallis Clinic, 3680 NW Samaritan Dr, Corvallis, OR 97330, USA. rtsolen@prodigy.net
authors.forename: Roland
authors.initials: R
authors.lastname: Solensky
authors.forename: Harry S
authors.initials: HS
authors.lastname: Earl
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Gruchalla
mesh_terms: D000328:Adult; D003362:Cost-Benefit Analysis; D004342:Drug Hypersensitivity / Q000175:diagnosis* / Q000276:immunology; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000032:analysis; D008297:Male; D008875:Middle Aged; D010404:Penicillin V / Q000008:administration & dosage / Q000009:adverse effects* / Q000276:immunology; D010406:Penicillins / Q000008:administration & dosage / Q000009:adverse effects* / Q000276:immunology; D011237:Predictive Value of Tests; D012882:Skin Tests / Q000379:methods*
chemical_list: D010406:Penicillins; D007073:Immunoglobulin E; D010404:Penicillin V