[Delayed hypersensitivity reactions to drugs: Group Report of the Drug Allergy Committee of the Mexican College of Clinical Immunology and Allergy (CMICA).]

Background: Adverse drug reactions are defined as unexpected reactions, either derived from the pharmacokinetics of the treatment (Type A) or as a host immune response (Type B), resulting in harmful or undesirable manifestations in the patient following the administration of pharmacological therapy. Type B reactions are less defined and are considered a result of hypersensitivity to pharmacological treatment, categorized as immediate (within 1 to 6 hours after exposure) and delayed or non-immediate (occurring 6 hours after exposure).

Objective: A review to describe the immunological mechanisms of delayed hypersensitivity reactions to drugs.

Methods: A search of major medical databases on delayed hypersensitivity reactions to drugs was conducted. The review was limited to articles published in the period between 2013 and 2023, taking into consideration articles written in English and Spanish.

Results: The terms defining delayed hypersensitivity reactions to drugs, their classification, clinical manifestations, diagnosis, treatment algorithms, and prognosis.

Conclusions: Adverse drug reactions represent a challenge for the specialist physician, with a complex pathophysiology. A prompt diagnosis and treatment focused on the drug phenotype and its immunological expression are required to provide a multidisciplinary approach.