there can be a cross-sensitivity: people who are allergic to penicillin could also be allergic to cephalosporin antibiotics (the class of drug for cefdinir). in my experience this rarely happens and i do use cefdinir in penicillin allergic patients unless their history reveals a severe (anaphylaxis) reaction in the past to penicillin. i have also found that many people who think they are allergic to penicillin are really not when they are tested. the bottom line: your doctor should prescribe it with caution and a warning but in many cases it would be just fine. recent studies have found that penicillin-allergic patients can take cephalosporin antibiotics safely but there is never a 100% certainty.
can i take cefdinir if i am allergic to penicillin?