I have a severe allergy to shell fish. my doc just prescribed keflex, because i am allergic to penicillin, too. i took a benadryl, (diphenhydramine) ?

? : There is a certain degree of cross reactivity between Keflex and penicillin. If one is getting an antibiotic and allergic to penicillin , i believe there are better choices i.E zithromax, Clindamycin etc. I am insure why you are being prescribed an antibiotic though in the first place. You did not indicate that you had an infection! you don't take an antibiotic for an allergic reaction.

See detail: Being allergic to shellfish and being allergic to antibiotics are two different things. They are not related. However, as the other doctor indicated, patients that are allergic to penicillin should not (in general) take keflex. Your shellfish allergy needs to be taken seriously and not only should you strictly avoid shellfish, you should carry injectable Epinephrine in case you have exposure.