Background:

Furosemide is the most commonly prescribed loop diuretic worldwide. Although, its extended use, furosemide rarely induces allergic reactions. Until 2013, only 49 cases of furosemide allergy had been described.

Clinical case:

We have reported on a patient who developed a delayed, erythematous and pruritic skin eruption after the ingestion of furosemide. The implication of furosemide in the reaction was established by a positive lymphocyte transformation test (LTT).

Conclusion:

This is the first reported case of hypersensitivity to furosemide in which this drug was confirmed as the trigger by a positive LTT. LTT could become a decent diagnostic alternative for patients who experience delayed reactions to furosemide.