Selecting Skin Testing Reagents to Predict Amoxicillin and Cephalosporin Allergy

Abstract

Objectives

This study assessed the accuracy of a panel of skin testing reagents to detect immunoglobulin E sensitivity to amoxicillin and oral cephalosporins.

Methods

One hundred and eighty-seven children and adolescents experiencing adverse reactions to amoxicillin (or amoxicillin/clavulanate), and/or an oral cephalosporin, that were considered sufficient to preclude further use were studied. Skin testing with penicillin G, commercial benzylpenicilloyl phosphate, penicillin minor determinant mixture (MDM), ampicillin, cefazolin, cefuroxime, and ceftriaxone was performed according to the suspected drug allergy, followed by an oral challenge, repeat skin testing, and prospective follow-up if no reactions were observed.

Results

Fifty-four (33.5%) of 161 patients with suspected amoxicillin reactions and 13 (50%) of 26 suspected cephalosporin reactions had positive skin tests or oral challenges. Positive reactions to only the MDM reagent occurred in 9 amoxicillin- or cephalosporin-allergic patients, to only the ampicillin reagent in 4 amoxicillin-allergic patients, and to only a cephalosporin reagent in 3 cephalosporin-allergic patients. No reactions to oral challenge were severe after negative skin testing. During prospective follow-up, one (0.9%) of 107 patients suspected of amoxicillin allergy who completed our skin testing—oral challenge repeat skin test protocol without a reaction and two (1.8%) patients with borderline reactions subsequently developed urticaria 8-16 months later while taking a course of amoxicillin. Reactions were mild. No test negative patients suspected of cephalosporin allergy developed a reaction with a subsequent course of a cephalosporin. Amoxicillin reactors with positive skin tests or oral challenges (N = 54) received 83 treatment courses of cephalosporins uneventfully in prospective follow-up.

Conclusions

Elective amoxicillin and cephalosporin skin testing and oral challenge protocols are helpful in identifying patients at very low risk for developing subsequent hypersensitivity reactions.