Does Eosinophilia While on Intravenous Antibiotics Portend a Hypersensitivity Reaction?

Eosinophilia occurs commonly in patients on antibiotics, but whether it is a risk factor for development of a hypersensitivity reaction (HSR) is unknown. To assess the frequency of and risk factors for antibiotic-induced eosinophilia — and subsequent HSRs — investigators in Boston studied a cohort of patients receiving outpatient intravenous antibiotics.

Of 824 patients, 210 (25%) developed eosinophilia (defined as an absolute eosinophil count ≥500/mL). Vancomycin, penicillin, rifampin, or linezolid use was associated with a higher risk for developing this condition. Sixty-four (30%) of the 210 patients subsequently manifested signs of an HSR. Compared to patients without eosinophilia, those with eosinophilia had a significantly higher likel…