Postponed Immediate Hypersensitivity Reaction to Ceftriaxone

Ceftriaxone is a widely used and generally safe 3rd generation cephalosporine. Immediate, IgE-mediated hypersensitivity reactions to ceftriaxone have been reported. We present a case of an elderly woman who received ceftriaxone 3 times over a period of 1 year. During the 1st course 1 year before the current event, the patient developed an atypical eruption on the seventh dose. Three months afterwards (9 months prior to the current event), unaware of the previous reaction, ceftriaxone was administered again. The first dose went uneventfully. Subsequently, being informed on the recent eruption, no second dose was administered. Noticing no hypersensitivity reaction to the unintentional re-challenge, skepticisms rose regarding the allergic nature of the former event. Nine months later (the current event), ceftriaxone was started for the third time. The 1st dose passed event-free, but after the second dose the patient mounted an immediate hypersensitivity reaction in the form of wide-spread urticaria. Postponed hypersensitivity reaction in this patient was explained by a three-step immune response: primary sensitization in earlier exposures, boosting the immune memory by 1st dose, to fast secretion of specific antibody, and the second dose to eliciting the immediate hypersensitivity reaction. We learned that on re-exposure of the sensitized patient the immediate hypersensitivity reaction may be postponed and that tolerance to the first dose of the antibiotic is no guarantee to being tolerant to the second dose.