Penicillin Allergy


Penicillin Allergy, Penicillin Adverse Drug Reaction

  • See Also
  • History
  • Reaction
  1. How old were you when you had the reaction?
  2. Did Type 1 Hypersensitivity Reaction symptoms occur?
    1. Anaphylaxis
    2. Hypotension
    3. Laryngeal edema (Wheezing or Stridor)
    4. Angioedema
    5. Urticaria
  3. How soon after the medication did the reaction start?
    1. Within one hour suggests Type 1 Hypersensitivity
  4. Was the Penicillin given orally or parenterally?
  5. Did the reaction resolve after stopping the medication?
  6. Have you taken related medications and did you react?
    1. Amoxicillin or Augmentin?
    2. Cephalosporin
  • Management
  1. Cephalosporins have cross reactivity with Penicillins
    1. Cross reactivity was originally over-estimated as high as 10% in the 1960s
      1. Attributed to cross contamination
      2. Co-production of Cephalosporins and Penicillins in the same factory
    2. Cephalosporin reaction when Penicillin Allergy
      1. Penicillin Allergy and allergy to first and Second Generation Cephalosporins: 1%
      2. Penicillin Allergy and allergy to Third Generation Cephalosporins: Negligible
      3. Aminopenicillins (Amoxicillin and Ampicillin) allergy
        1. Cross-reactivity to first and Second Generation Cephalosporins: High
        2. R1-side chain of Aminopenicillins are similar to first and Second Generation Cephalosporins
        3. Reaction rate is as high as 27% for Cefadroxil
      4. Campagna (2012) J Emerg Med 42(5): 612-20 [PubMed]
    3. Penicillin Allergy when Cephalosporin allergic: >25%
    4. Cephalosporin cross reactivity risk factors
      1. Type I Hypersensitivity to Penicillin
      2. Positive Penicillin skin test (5% risk)
      3. First or second generation Cephalosporin
      4. Atopic Dermatitis
  2. Reaction not consistent with Type I Hypersensitivity
    1. Consider Penicillin Skin Testing for allergy
    2. Continue to avoid Penicillins unless otherwise directed by allergy Consultation
    3. Cephalosporins may be used
      1. Some recommend penicillin Skin Testing before use
      2. Kelkar (2001) N Engl J Med 345:804-9 [PubMed]
  3. Type I Hypersensitivity Reaction
    1. Obtain Penicillin Skin Testing for allergy
    2. Penicillin skin test negative (80-95% of cases)
      1. Cephalosporins may be used (1.3% risk of reaction)
      2. Continue to avoid Penicillins unless otherwise directed by allergist
    3. Penicillin skin test positive
      1. Avoid Penicillins and Cephalosporins
      2. Risk of Cephalosporin reaction: 4.4%
      3. Consider cephalosporin Desensitization
  • Complications
  1. Documented Penicillin Allergy is associated with adverse events due to alternative antibiotic use
    1. Confirm allergy and document actual Penicillin reaction
    2. Results in overuse of broad spectrum agents
    3. Associated with longer hospital stay and increased C. Diff and MRSA Infections
    4. Macy (2014) J Allergy Clin Immunol 133(3): 790-6 +PMID:24188976 [PubMed]