A diuretic that does not contain a sulfonamide group can be used safely in someone with a sulfa allergy. In addition to ethacrynic acid (Edecrin) these include amiloride, triamterene, spironolactone, and eplernone. It is also unclear whether or not there is significant cross-reactivity, between someone with an allergy to a sulfa antibiotic and a sulfa diuretic, so other medications may be safe as well. Talk the options over with your doctor.