Abstract
Trimethoprim-sulfamethoxazole (TMP-SMX) is a non-β-lactam antibiotic commonly used in pediatrics to treat infections and as a prophylactic medication. Hypersensitivity to TMP-SMX is generally non-immediate, and immediate allergic reactions, including anaphylaxis, are rare. This case report details a six-year-old girl who experienced anaphylaxis to TMP-SMX. Her skin prick test with TMP-SMX was negative, but she developed anaphylaxis in a drug provocation test (DPT). An additional basophil activation test (BAT) for the TMP-SMX combination tablet was evaluated and was confirmed positive. This case underscores the need for alternative diagnostic methods like BAT, which pose a lower risk than DPT. The findings suggest that BAT could offer a safer diagnostic approach, though more studies are required to validate its use for TMP-SMX allergy diagnosis.