Allergic reactions to cephalosporins

Allergic manifestations The cephalosporins should be avoided or used with caution in individuals allergic to penicillins (about 5 to 15% show cross-sensitivity). In contrast, the incidence of allergic reactions to cephalosporins is 1-2% in patients without a history of allergy to penicillins. 

Note Penicillin and cephalosporins share a common beta-lactam structure. People who are allergic to penicillin are approximately 4 times more likely to develop an allergic reaction to a cephalosporin than those people who have no penicillin allergy. (From 5 to 16% of patients allergic to penicillin develop allergic reactions to cephalosporins)... 

All cephalsoporins have a 7-amino-cephalosporanic group (cephem nucleus). They differ by a C7 and a C3 substitution. The cause of allergic reaction to cephalosporins can be the cephem nucleus itself, but this seems to be rare. Allergic contact dermatitis from cephalosporins is uncommon and mainly occurs in healthcare, pharmaceutical and veterinary professions. 

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