I am allergic to penicillin and sulfa drugs. I am worried that if I become ill in the future, I may not be able to be cured because of these allergies.

Ken B.

I encounter concerns about antibiotic allergies often. Many times, when a patient states that he or she is allergic to penicillin, testing would prove that this is not really the case. Sometimes, patients believe they are allergic to penicillin because their parents noted a rash when they took the drug as a child. But in many instances, the rash was from the illness that prompted use of an antibiotic in the first place. Unfortunately, it is difficult to determine in an office setting who is truly allergic, and we usually choose the simplest approach -- avoiding that class of antibiotics.
There is a tremendous selection of antibiotics available to physicians. However, this multitude of choices is limited to a handful of classes of drugs. Drugs in any one class may have a similar risk of allergy and other side effects. If you had a severe allergic reaction to penicillin, it may be unwise to give you any drug from the entire class of penicillins and as well as the cephalosporins (a class very similar to the penicillins), as there is a risk of allergic cross-reactivity between these two groups. (Cephalosporins include cephalexin, or Keflex, and cefaclor, or Ceclor.) Only a few antibiotics are in the sulfa class, so that may not be a big deal at all. Still, not using penicillins, cephalosporins and sulfa drugs would eliminate close to 100 choices from the antibiotic armamentarium.

Even in your case, there are still quite a few antibiotic choices left. Most infections that you would develop later in life could be treated with the fluoroquinolone class. This class includes ciprofloxacin (Cipro), levofloxacin (Levaquin) and the newer drugs moxifloxacin (Avelox) and gatifloxacin (Tequin). We could also use the tetracycline class and the macrolides erythromycin (E-mycin), clarithromycin (Biaxin) and azithromycin (Zithromax). There are also other choices from other classes that would be safe for you to take.