Algorithm for Suspected Penicillin Allergy in Patients Undergoing Surgery 


• Cephalosporins may be prescribed to patients with reported penicillin allergy if physicians use 

the clinical decision support algorithm below. 
• If the reaction to penicillin occurred more than 10 years ago, the likelihood of a reaction to 

a cephalosporin is low due to diminished lgE levels.
• Only 10% of all patients who report a penicillin allergy are diagnosed as skin-test positive: Of 

those who are skin-test positive, there is only a 2% cross-reactivity rate with cephalosporins for 

patients who have a true penicillin allergy 2 (i.e. 0.2% of all patients reporting allergy). 
• Overall there is less than a 1 in 100,000 risk of anaphylaxis with a cephalosporin in patients 

reporting a penicillin allergy. 


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