Immediate allergic reactions to betalactams: facts and controversies

To analyse the available data in the field of immediate allergic reactions to beta-lactams, with particular emphasis on more recent studies, and to comment on the future role of this group of antibiotics.

The world of beta-lactams has become more complex than initially thought, due to the increased number of chemical structures available, the wide variety of indications for their use in treating different infectious diseases, and possibly also due to the interaction of other as yet undetermined factors. Benzyl penicillin, the original inducer of allergic reactions, has now largely been replaced by amoxicillin and, to a lesser extent, by cephalosporins in inducing IgE-mediated allergic reactions. These structures often share extensive cross-reactivity, eliciting clinical reactions to many compounds, especially amongst penicillins. In other circumstances selective responses are observed which are restricted to one group or one single compound, as occurs in the group of cephalosporins. The application of new determinants for skin testing and the use of adapted in-vitro studies have enabled these findings to be confirmed in detail.

Results indicate that evaluation of immediate reactions to beta-lactams requires the use of several determinants for both in-vitro and in-vivo testing, and which must reflect the relevant drug involved in eliciting the response. This tendency will be strengthened in the future if use of benzyl penicillin continues to decrease as a drug to which populations are exposed.