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Doctor insights on: I'm Allergic To Penicillin Can I Take Cephalexin 500mg

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Is it possible for you to take cephalexin if you r allergic to penicillins?

Is it possible for you to take cephalexin if you r allergic to penicillins?

Yes: Cross reactivity between the two classes are low so Cephalexin is not contraindicated in penicillin allergy patients. You should have your prescribing physician to follow you for any signs of reactions and get proper treatment. ...Read more

Dr. Milton Alvis Jr
285 doctors shared insights

Keftabs (Definition)

Keftabs is a first generation cephalosporin which is a kind of cephalosporin type drug (anti-bacterial ...Read more


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Can I take cephalexin if I am highly allergic to penicillin? I have not taken penicillin since I was very young. Reaction of hives convulsions

Can I take cephalexin if I am highly allergic to penicillin? I have not taken penicillin since I was very young.  Reaction of hives convulsions

Penicillin allergy: You have what is known as an immediate hypersensitivity reaction to penicillin derivatives and should never be given one, since this is life-threatening. There is said to be cross-hypersensitivity reactions to cephalosporins in 5% of pen allergic persons, and 0.1% of these have a severe reaction. My advice would be not to take a cephalosporin antibiotic unless there was no alternative. ...Read more

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I'm allergic to penicillin, can I take keflex?

I'm allergic to penicillin, can I take keflex?

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. ...Read more

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Allergic to penicillin can I take keflex?

Likely, not certain: The majority of people who are told they are allergic to penicillin are not actually so (they get rashes for other reasons, e.g.). Of those that are allergic, about 70% or more will lose the allergy after about 10 years. If you are still allergic, there is about a 10% chance of cross-reaction to 1st-gen cephalosporins like keflex. An allergist can perform testing to judge your risk for a reaction. ...Read more

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If i'm allergic to penicillin is it safe to take keflex pulvales?

If i'm allergic to penicillin is it safe to take keflex pulvales?

No: If you are truly allergic to penicillin, you should avoid all penicillin derivatives and the first generation cephalosporins. Keflex is a first gen. Cephalosporin and may cross react with penicillin. See a board certified allergist to help you determine if penicillin is a true allergy for you. ...Read more

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I m allergic to penicillin keflex azithromiacin my daughter has scarlet fever and i m worried about what i can take if i get it ?

I m allergic to penicillin keflex azithromiacin my daughter has scarlet fever and i m worried about what i can take if i get it ?

Don't panic: Scarlet fever is an acute febrile illness, primarily affecting children, caused by group a beta-hemolytic streptococci. Clinical manifestations include fever, sore throat, and fine sand-paper like rash caused by a toxin produced by the strep. Although penicillins are antibiotics of choice, there are other antibiotics that are effective. Your doctor will know. A throat culture is helpful. ...Read more

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Is it a bad idea for someone allergic to penicillin safely take keflex, a cephalosporin?

Yes: Cephalexin (keflex) is a first generation cephalosporin and a very close cousin to penicillin. Though it is not 100% true that all penicillin allergic individuals are also allergic to cephalexin, there is a high likelihood of that happening. ...Read more

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I'm allergic to penicillin. Was prescribed cephalexin for folliculitis. Stop taking it 3 days ago. Now I have hives all over. Delayed reaction?

Possible: A small % of people who are allergic to penicillin may also react to cephalosporin such as cephalexin. However, if your reaction did not occur until about 10 days after you started to take the medication, this may well be a true allergic reaction specific to cephalexin. ...Read more

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I started taking cephalexin. As I have had mild allergic reaction to penicillin , should I expect serious allergic reactions to this medicatiion?

I started taking cephalexin. As I have  had mild allergic reaction to penicillin , should I expect  serious allergic reactions  to this medicatiion?

Mostly not: The incidence of cephalexin allergy in patients with penicillin allergy is in the single digit % and likely not much different from patient without a history of penicillin allergy. However if you had a severe anaphylactic reaction to penicillin, I would suggest an allergy consult just to be safe . ...Read more

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If I got an allergic reaction from cephalexin, does that mean I am also allergic to penicillin?

If I got an allergic reaction from cephalexin, does that mean I am also allergic to penicillin?

No: There is indeed crossreactivity, but: -if you are allergic to cephalosporins like cephalexin, and have had penicillin with no problem in the past, most patients can continue taking penicillin without problems. -if you have not had penicillin since this reaction to cephalexin, you should see a physician who could to test you to penicillin, ideally an allergist. ...Read more

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I'm allergic 2 penicillin/prescribed cephalexin 4 a cellulitis infection in my arm from a iv. How fast would a serious reaction occur if allergic ?

I'm allergic 2 penicillin/prescribed cephalexin 4 a cellulitis infection in my arm from a iv. How fast would a serious reaction occur if allergic ?

Minutes to hours: A small proportion of penicillin allergic patients can have an allergic reaction to cephalexin. Drug allergic reactions can occur in minutes to hours if already sensitized. It is possible to develop serious allergic reactions after several days of being on the medication and in some cases even shortly after stopping the med. Allergy testing is available for penicillin but not cephalexin. ...Read more

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I have a whitehead abcess beside a broken tooth. When i was a child I broke out from penicillin. And I dont know if i can take cephalexin.. Can I?

I have a whitehead abcess beside a broken tooth. When i was a child I broke out from penicillin. And I dont know if i can take cephalexin.. Can I?

Abscess/Cephalexin: This sounds like a dental abscess. Use warm compresses frequently to encourage it to drain. Allergy to Penicillin is often over diagnosed so at some point look into it further. Cephalexin is not considered a good alternative if you have a Penicillin allergy. A medication called Clindamycin would be a better choice. Be sure to see your dentist to manage your abscess and your broken tooth. ...Read more

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ER doctor prescribed me Keflex for possible mastitis and UTI knowing I'm allergic to penicillin. I am on day 3 and have an itchy rash on arms and legs?

ER doctor prescribed me Keflex for possible mastitis and UTI knowing I'm allergic to penicillin. I am on day 3 and have an itchy rash on arms and legs?

Possibly allergic: Cephalexin (Keflex) and related antibiotics (the cephalosporin group) are chemically similar to penicillinl. Although penicillin allergic persons usually can take them without problem, occasional cross reactions occur -- i.e. you may be allergic to the cephalexin. Check with the doctor who prescribed it. ...Read more

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I am allergic to keflex & penicillin. Is neosporin still ok to use on my skin?

Neosporin: People have a tendency to assume that neosporin does not cause side effects because it is a widely available and frequently used nonprescription product. However, this is simply not the case. In fact, many healthcare providers now recommend that people avoid products with neomycin (including neosporin), as neomycin is more likely than most other antibiotics to cause allergic reactions. ...Read more

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Always fine w penicillin, but had extreme allergic reaction reaction to keflex! does that mean I am now also allergic to penicillin for sure?

Always fine w penicillin, but had extreme allergic reaction reaction to keflex! does that mean I am now also allergic to penicillin for sure?

Not necessarily: While penicillin and Cephalexin (keflex) share some features, allergy to one does not necessarily to one mean that you are allergic to the other. See a board-certified allergist/immunologist to sort things out. ...Read more

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Was recently dx'd with lupus & am allergic to Keflex. Heard that lupus patients tend to have strong reactions to penicillin, should I avoid penicilin?

Avoid penicillin: I am not aware of the connection between allergy to PCN and lupus, You need to avoid PCN if you are allergic to keflex. ...Read more

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I got allergy from penicillin 45 yrs ago when I was 8 yrs, since then I have not used it. Now due to UTI I am given keflex. Shd I take it. Advice plz?

I got allergy from penicillin  45 yrs ago when I was 8 yrs, since then I have not used it. Now due to UTI I am given keflex. Shd I take it. Advice plz?

Usually okay.: We were taught for years that there is about a 10% risk of being allergic to cephalosporins (like Keflex) in people who were allergic to drugs in the penicillin family. Later research has said that is a myth, and there is less than a 1% risk depending on the type of cephalosporin. See http://www.ncbi.nlm.nih.gov/pubmed/21742459. Talk to your doctor about your fears, though. ...Read more

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