Diagnosing β-Lactam Hypersensitivity

Hypersensitivity reactions to β-lactam antibiotics are commonly reported. They can be classified as immediate or non-immediate according to the time interval between the last drug administration and their onset. Immediate reactions occur within one hour after the last drug administration and are manifested clinically by urticaria and/or angioedema, rhinitis, bronchospasm, and anaphylactic shock; they may be mediated by specific IgEantibodies. Non-immediate reactions occur more than one hour after the last drug administration. The most common manifestations are maculopapular exanthemas; specific T lymphocytes may be involved in this type of manifestation. In the diagnostic evaluation of hypersensitivity reactions to β -lactam antibiotics, the patient’s history is fundamental. The allergy examination is based on in vitro and in vivo tests selected on the basis of the clinical features and the type of reaction, immediate or non-immediate. Immediate reactions can be assessed in vitro by serum specific IgE assays and basophil activation tests and in vivo by immediate-reading skin tests and, in selected cases, drug provocation tests (DPTs). Non-immediate reactions can be evaluated mainly by delayed-reading skin tests, patch tests, and DPTs.