Are you, by any chance, allergic to sulfa drugs? My sister had a similar reaction to hydrochlorothiazide (HCTZ), and the doctor said it was because she was allergic to sulfa. My sister had not put her sulfa allergy on her medical history form at the cardiologist's office, because the sulfa reaction had been so long ago. When the doctor prescribed HCTZ, which evidently has sulfa in it, my sister reacted to that.