Drug allergy de-labelling with a direct oral challenge in outpatient hospital visits

Abstract Although direct oral challenge has been adopted by numerous clinicians worldwide in the context of drug hypersensitivity, drug allergy de-labelling remains largely confined to inpatient or outpatient hospital-based care,mostly for penicillins. In this study, we aim to perform direct oral drug challenge (DODC) in outpatients with low-risk allergy to drugs (not only penicillin) in outpatient visits in a specialized allergy clinic. We conducted a prospective single-centre study from May 2022 to January 2024. Inclusion criteria were age ≥14 years and a label of drug allergy. Exclusion criteria were anaphylaxis or severe cutaneous adverse drug reactions or prior skin tests to the suspected drug. The culprit drug was given as a standard single dose in an outpatient hospital visit. In total, 304 patients were included. Penicillins were the most frequent culprit drugs with 228 (75%) patients. The other drugs involved in allergy labelling were as follows: nonsteroidal anti-inflammatory drugs (NSAIDs) in 31 (10.2%) patients, cephalosporins in 10 (3.3%) patients, other antibiotics in 15 (4.9%) patients, analgesics in 7 (2.3%) patients and corticosteroids in 4 (1.3%) patients. Nine (3.0%) patients had a reaction to other drugs. Among the whole cohort, 295 (97.0%) had no reaction during DODC. Nine patients presented with a mild reaction including three with an immediate reaction and six with a delayed reaction. In conclusion, allergy de-labelling to all drugs in patients with low-risk allergies can be safely conducted in outpatient visits. However, a risk stratification needs to be clarified with a validated tool for patients’ selection.