In the last years, immediate reactions to quinolone antibiotics have been observed with increasing frequency, mainly urticaria, angioedema, and shock. No test was available because of the high incidence of false-positive results on skin tests. Thus the pathogenesis, value of diagnostic procedures, and cross-reactivity have not been evaluated in a systematic way.

We sought to assess whether these reactions are IgE mediated and whether an in vitro test for quinolone-specific IgE is useful in the diagnosis and understanding of cross-reactivity.

We assayed specific serum IgE to quinolones using epoxy-activated sepharose 6B as the solid phase in 55 patients with immediate adverse reactions; specificity of IgE binding was demonstrated by inhibition tests.

The test yielded positive results in 30 (54.5%) patients who were tested 1 to 48 months after the reaction had occurred. The quinolone-specific IgE seems to disappear more slowly in atopic patients. The cross-reactivity between various quinolones allowed us to identify a common structural motif within quinolones that might be responsible for clinical and serologic cross-reactivity.

A substantial portion of immediate reactions to quinolones appear to be IgE mediated. Cross-reactivity of IgE among different quinolones is frequent and suggests that a common avoidance of quinolones should be attempted in all patients with respective symptoms.