Can i take erythromycin if i am allergic to both ampicillin & penicillin?

For what?: Ampicillin is part of the penicillin class of antibiotics. While Erythromycin is usually considered an alternative antibiotic with individuals who are allergic to penicillin, here is the key point: we don't know anything about your medical history, what medications you are taking and what you need antibiotics for. Therefore- only a health care provider should prescribe medications for you!

Yes: No problem--no cross reaction--totally unrelated drugs.