I'm allergic to penicillin, will other antibiotics work against a streptococcal b infection?

Either...: Macrolides such as Azithromycin for a mild infection, or Clindamycin for a more serious one. Cephalosporins affect about 10% of people allergic to penicillin, and so may also be a reasonable choice.

Yes: There are a number of effective antibiotics that your doctor can choose. Most patients who think that they are allergic to penicillin are not. Even patients who had a reaction in the past usually lose the allergy. An allergist can test to see if you are allergic.