Delayed positive drug provocation tests to beta‐lactams with flare‐up reactions of skin tests sites.

Clinicians working in drug allergy should be aware of this unusual delay, since these may be true drug allergies, confirmed by flare-up of primarily negative skin tests. Delayed positive drug provocation tests to beta-lactams with flare-up reactions of skin tests sites Keywords: beta-lactams; drug allergy; Flare-up; T cells; test EN beta-lactams drug allergy Flare-up T cells test 499 502 4 03/08/21 20210301 NES 210301 To the Editor, Non-immediate allergic drug hypersensitivity reactions (DHR) to beta-lactams are attributed to T-cell-dependent mechanisms, varying from mild/moderate reactions, such as maculopapular exanthema (MPE) or delayed urticaria, to more severe cutaneous adverse reactions (SCAR).1 Patch tests (PT) and/or delayed-reading intradermal tests (IDT) have been proposed for in vivo diagnosis of this allergic phenotype, with the latter being generally reported as more sensitive.1 When skin tests are negative and there is no contraindication, a drug provocation test (DPT) may be performed, to confirm or rule out the DHR. [Extracted from the article]