Cephalosporin allergy.

Allergic reactions to cephalosporins may occur because of sensitization to cephalosporin determinants shared with penicillin or to unique cephalosporin haptens. The exact nature of the haptenic determinants resulting from the degradation of currently available cephalosporins is incompletely understood. Cephalosporin skin testing or specific IgE immunoassays have limited clinical utility. Patients with a history of allergy to cephalosporins or penicillin may be at increased risk for a reaction to cephalosporins. Skin testing for an allergy to penicillin may be helpful in patients with a history of penicillin allergy who have a clinical indication for cephalosporin use. Most of these patients have negative tests and should not be at increased risk for a reaction to cephalosporins.