Penicillin Allergy

Aka: Penicillin Allergy, Penicillin Adverse Drug Reaction

1. See Also
   1. Penicillin
2. Reaction History
   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
3. Management
   1. General
      1. Cephalosporins have cross reactivity with Penicillins
         1. Rate of Cephalosporin allergy
            1. Patients without Penicillin Allergy: 2%
            2. Patients with Penicillin Allergy: 8%
         2. Cephalosporin reaction more severe in atopics
      2. Cross reactivity risk factors
         1. Type I Hypersensitivity to Penicillin
         2. Positive Penicillin skin test (5% risk)
         3. First generation Cephalosporin
   2. Reaction not consistent with Type I Hypersensitivity
      1. Continue to avoid Penicillins
      2. Cephalosporins may be used
         1. Some recommend penicillin Skin Testing before use
         2. Kelkar (2001) N Engl J Med 345:804-9
   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
      3. Penicillin skin test positive
         1. Avoid Penicillins and Cephalosporins
         2. Risk of Cephalosporin reaction: 4.4%
         3. Consider Cephalosporin desensitization
4. References
   1. Kelkar (2001) N Engl J Med 345:804-9
   2. Salkind (2001) JAMA 285:2498-505