ALLERGY TO BETALACTAMS

Allergy to betalactams is the most common drug allergy in the pediatric population. However, in most patients with a clear positive history the tests results are negative and the diagnosis of allergy is established only in a small percentage of cases. Still, most children labelled as "allergic to penicillin" are not truly allergic, and without a proper study, this label usually perpetuates to adulthood.

These reactions can be classified as immediate and non-immediate. The immediate reactions occur up to one hour after the drug administration and they are mediated by IgE antibodies. The non-immediate reactions usually occur more than one hour after the administration and they are mediated by specific T-cells.

The diagnostic approach for the hypersensitivity reactions is complex and extensive. The clinical history is crucial and the choice of the proper diagnostic tests to perform is based on the symptoms and clinical signs. Currently, the diagnosis is mostly assessed by using skin tests (to exclude an IgE-mediated allergy), and in negative skin test patients by a drug provocation test, considered the gold standard. The skin tests reveal a good sensibility and are used as a first-line procedure in the evaluation of betalactams allergy. Determination of specific-IgE is the most used in vitro test in the diagnosis of immediate reactions. New tests with promising results are been developed, but still require further data and are not routinely recommended in the pediatric population. The drug provocation test is often the only reliable way to establish a diagnosis, and should be considered particularly in cases of children who develop a delayed-onset urticarial or maculopapular rash during treatment with a betalactam.