Sulfa allergy: Which medications should I avoid?

How can I tell if a medicine contains sulfa? Should I simply avoid those with ingredients that have the prefix "sul" or "sulfa"? . . Avoiding only medications with the prefix "sul" or even "sulfa" is not a good rule of thumb if you have a sulfa allergy. The term "sulfa allergy" is most often used to describe an adverse drug reaction to antibiotics that contain sulfonamides. Generic names or brand names of medications that contain sulfonamides may not start with "sul" or "sulfa." . . read more.