Why am I allergic to Penicillin?

Why am I allergic to Zithromax but not Penicillin?

• All my doctors are puzzled about this since Zithromax is actually meant for people who have a lot of allergies including ones to penicillin yet I'm not allergic to pencillin... I'm really interested if any one knows why this could be?

• Answer:

  I don't know why your doctors would be puzzled by this. Zithromax, like you said, is often prescribed to those who ARE allergic to Penicillin. Meaning that most people are allergic to one, and not the other. Just because you are allergic to the one most people aren't.....that doesn't mean you should automatically be allergic to both. They are two different kinds of antibiotics. Penicillin (like Ceclor and Amoxacillin) is a cephalosporin, while Zithromax, or azithromycin, is a macrolide. That's why it is possible to be allergic to one and not the other. Although generally people are allergic to Penicillin and not Zithromax (like myself) it is not unheard of to be the opposite.