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Most People with a penicillin allergy can safely take cephalosporins
Rod Moser, PA, PhD posted:
Medical providers have always been taught that if you are allergic to penicillin, you have a greater chance of also being allergic to a large class of antibiotics called cephalosporins (Keflex, Suprax, Omnicef, Cefzil, Ceftin, etc.). Not wanting to cause the patient another, potentially-serious adverse reaction, many clinicians automatically eliminate cephalosporin use in patients who report a penicillin allergy. A study of 156 penicillin-allergic patients reported at the American Academy of Allergy, Asthma, and Immunology, found that 80 people tested negative to penicillin allergy, and only ONE PATIENT out of 156 experienced a possible, mild adverse reaction.
TIP #2: Not all adverse reactions to drugs, even rashes, are ALLERGIC. Amoxicillin ? a penicillin derivative ? is notorious for causing a non-allergic, skin rash in some people. Clinicians typically will avoid giving it again, but to eliminate cephalosporins as an alternative drug may not be prudent.
TIP #3: Viruses often cause rashes, especially in children, so if a child is taking amoxicillin and develops a rash, it does not necessarily mean it is from the drug. However, if a child develops HIVES, this is most-likely a penicillin allergic response.

TIP #4: Not all adverse reactions are ALLERGIC reactions. Getting a tummyache or diarrhea while taking an antibiotic does not mean you are "allergic" to it.

Always inform your medical provider of possible allergies AND adverse drug reactions so that a reasonable, informed decision can be made regarding the use of the same or similar medications in the future.
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marg01 responded:
Good to know. This is the first time I've read the information about Amoxicillin. I have a rather allergic son (several food allergies and some environmental as well.) When my son was five I took him to his Pediatrician to get him updated on his vaccines. While we were there the doctor noticed he had impetigo in his nose. She prescribed Amoxicillin. It would be his first time taking any kind of antibiotic. I asked if I should bring him back when he was better to get his vaccines, she said no, it wasn't a problem and gave him MMR in one arm and another multidose shot in his other arm. I can't remember off hand what that contained - Polio comes to mind. Anyway, he developed some swelling on his right arm which I thought was normal. After several days that swelling developed into flat, red, non-itchy marks that started on his arms and trunk and then continued down his legs and finally his face (none on his hands or feet). So when this started happening I called the Pediatrician to ask for her to see him, describing what was happening. The nurse I spoke with told me there was no way they would be able to figure out what was going on and basically refused to see him. I was miffed. I researched and was thinking it was either a reaction to the MMR or Amoxicillin. I called his allergist and talked it over and we decided to consider him allergic to Amoxicillin. The marks subsided after a week. Maybe he's not allergic after all... I may bring him in for more testing!
MidwestGal responded:
Living proof. I am allergic to penicillin (severe hives and rash) but I can take Keflex without any issues.
Rod Moser, PA, PhD replied to MidwestGal's response:
Thanks for the comment....

Our computer at work still sounds a warning alarm if I try to prescribe Kelfex to a penicillin-allergic patient. Incidentally, many penicillin-allergic patients when given a allergy test for this drug, are NOT allergic to penicillin. They have have gotten a non-allergic rash as a child while taking it, and it was just assumed they are allergic.

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