Furosemide, one of the most used diuretic drugs, rarely induces type-1 allergic reactions It is included in the non-aromatic sulfonamides but a cross-reactivity mechanism between this group and the sulfonamides antibiotics, has not been clearly demonstrated. A 24-year-old woman, 10 minutes after the intake of one pill of Seguril 40mg experienced oral itching, generalized urticaria, facial angioedema, dyspnea and hypotension. She recovered after the administration of parental adrenaline, methyl-prednisolone and dyphenhydramine. An skin prick test with furosemide (10 mg/ml) was negative. The intradermal skin tests were positive to furosemide (1 %) as well as sulfamethoxazole (0.03 mg/ml), with 10 atopic and non-atopic negative controls. The patient rejected the performance of an oral challenge test with sulfamethoxazole. IgE-mediated reactions to furosemide are infrequent, but it could be the cause of life-threatening reactions. We have reported a case of anaphylaxis after the oral administration of furosemide with a demonstrated hypersensitivity mechanism through the positive intradermal skin test. The previous administration of the drug could probably the mechanism of sensitization, but the positive intradermal test to sulfamethoxazole would open the hypothesis of a cross-reactivity between non-aromatic and antimicrobial sulfonamides. It could be necessary an oral challenge test with furosemide in allergic patients to sulfamides.