A 21-year-old member asked:
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i'm allergic to penicillin, can i take keflex?

2 doctor answers
Dr. Alex Martinez
Specializes in Allergy
Maybe: Penicillins (like amoxil) & cephalosporins (like keflex) are both beta-lactam antibiotics named because of their ringed chemical structure. Allergy to penicillins is sometimes directed against this ring, and an allergic reaction may also occur if a similar antibiotic is taken. It is estimated that about 10% of penicillin-allergic patients are also allergic to cephalosporins like keflex.
Answered on Dec 7, 2019
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Dr. Gary Moss
Dr. Gary Moss answered
28 years experience Allergy and Immunology
Probably: Most doctors are concerned about cross reactivity between penicillins and cephalosporins, including keflex. In actuality, the cross-reactivity is uncommon between these two classes. Also, most people who think that they are allergic to penicillin are not. An allergist can test to see wether you are allergic to penicillin. He could also confirm whether it would be safe to take keflex.
Answered on Dec 7, 2019
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