Penicillin Allergy

All drug allergies must be documented on the medication chart, with the patient’s reaction

• The diagnosis of penicillin allergy is often accepted without obtaining a detailed history of the patient’s reaction. As a result, penicillins may unnecessarily be withheld from some patients who do not have a true allergy. This may adversely affect their clinical outcome.   
  
  
• The clinical symptoms of a true Type I allergy to penicillin are urticaria, laryngeal oedema, bronchospasm, hypotension, or local swelling within 72 hours of administration or development of a pruritic rash even after 72 hours. These patients should not receive a penicillin.
  
  
• Patients with a history of intolerance to penicillin e.g. Gastro-intestinal upset, after administration are probably not truly allergic to penicillin.       
  
  
• The frequently cited figure of 10% cross reactivity between penicillins and cephalosporins is thought to be an overestimate.  The true incidence of cross-sensitivity is uncertain. It is thought that first generation cephalosporins have a greater risk of cross-sensitivity than second or third generation cephalosporins.
  
  
• Patients with Type I allergy should avoid cephalosporins and other beta-lactam antibiotics for non-severe infections if a suitable alternative exists.  In life threatening infections, when the use of a non beta-lactam antibiotic would be sub-optimal, consideration can be given to a second or third generation cephalosporin or meropenem under close observation.  Seek advice from Microbiology.