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Doctor insights on: Allergic Reaction To Keflex

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I had a severe allergic reaction to keflex. Can i trust taking other antiobios in the future without being pre-tested? How to know if allergic again?

I had a severe allergic reaction to keflex. Can i trust taking other antiobios in the future without being pre-tested? How to know if allergic again?

Many options: Antibiotics are in a number of chemical classes. With a severe reaction to Keflex (also called cefazolin), you should avoid antibiotics in the cephalosporin and probably the penicillin class, as there is a higher chance of cross reactivity. Typically, we will give antibiotics in a different chemical class rather than testing. For you, examples may be clindamycin, Ciprofloxacin or vancomycin. ...Read more

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Dr. John Chiu
2,573 doctors shared insights

Allergies (Definition)

Allergies occur when your immune system is triggered by envirionmental factors it should ignore--for example, pollen in the air, or dander on a cat or dog--and creates cells to fight against them. An allergic reaction typically causes itching, congestion, or drainage, and ...Read more


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My 2 1/2 year has an allergic reaction to keflex has hives all over body how much Benedryl can I give her she is 28 lbs ?

My 2 1/2 year has an allergic reaction to keflex has hives all over body how much Benedryl can I give her she is 28 lbs ?

Benadryl (diphenhydramine) dosing: Benadryl (diphenhydramine) is effective between 0.5 to 1.0 mg/kg per dose every 8-12 hrs. Based on pt being 28 lbs then a tspn of benadryl (diphenhydramine) 12.5mg/5ml will give pt 12.5 mg which is about 1 mg/kg. ...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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I was given Keflex around 3 months ago for Hidradenitis. I had an allergic reaction and stopped taking it . I've had hives ever since. Why is that?

I was given Keflex around 3 months ago for Hidradenitis. I had an allergic reaction and stopped taking it . I've had hives ever since. Why is that?

Not Keflex: HIves is a particular kind of rash, and rarely lasts more than a few days. And any rash due to cephalexin (Keflex) allergy would not last more than 1-2 weeks after stopping the drug. So whatever the cause of your current rash, it probably isn't hives and cephalexin isn't the cause. If you're taking any other medications, you might be allergic to one of them. Discuss with your doctor. ...Read more

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Why would i suddenly have so many med allergies (hives, etc?) allergic to nsaids, opiates, keflex, and more. All within a couple yrs. Why?

Why would i suddenly have so many med allergies (hives, etc?) allergic to nsaids, opiates, keflex, and more. All within a couple yrs. Why?

It is uncommon: First you need to describe what kinds of problem you have had with each of the drugs since some may not really be from an allergy. Becoming "allergic" to drugs with unrelated chemical structure in 2 years is also rare. You need to consult an allergist to help you sort this out. ...Read more

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How can you know if have an allergic reaction to cephalexin ?

How can you know if have an allergic reaction to cephalexin ?

Timing, symptoms: There are different kinds of reactions one can have to antibiotics. There are many factors in the history which help diagnose this (timing of the reaction in proximity to the antibiotic, oral/iv, past history, family history). An allergist can perform testing to help confirm Cephalexin allergy if necessary. ...Read more

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Cephalexin side effects and safety? Allergic reaction risk?

Cephalexin side effects and safety? Allergic reaction risk?

Urticaria: Cephalexin is an oral antibiotic, belongs to the class of 'cephalosporin'. People who are allergic to 'penicillin" in general, will have cross sensitivity reaction to cephalosporin as well. The drug reaction can vary from mild urticarial rash to severe anaphylaxis, which will be life a threatening situation. Sometimes cephalosporin can give 'drug induced fever' as well. Good luck ! ...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?

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?

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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Had an allergic reaction to cephalexin though i took it before and was fine. I discontinued use and prescribed macro bid for a uti. Similar symptoms.?

Had an allergic reaction to cephalexin though i took it before and was fine. I discontinued use and prescribed macro bid for a uti. Similar symptoms.?

Antibiotic allergies: Many people react to two+ medications. If you just took the Cephalexin and had the reaction, your current apparent reaction to the Macrobid could be a continuation of the Cephalexin reaction.Sometimes, if the reaction is a mild rash and you aren't very sick, the best thing to do is take an antihistamine and continue the drug. Call the doctor who prescribed both meds for you, or an allergist. ...Read more

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Tue..I was prescribed cephalexin 4 cellulitis. This morn I noticed red spots in multiple places on body. Allergic reaction / course of action?

Tue..I was prescribed cephalexin 4 cellulitis. This morn I noticed red spots in multiple places on body. Allergic reaction / course of action?

Allergic reaction: Not being able to see the rash I have to conclude that this is an allergic to the cephalexin and you should stop it immediately. The good news is that this does not mean you are allergic to other cephalosporins or pencillins according to more recent findings. Contact your doctor to get the right drug for you. ...Read more

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How long until i see the effects of prednisone for an allergic reaction to cephalexin , severe rash?

How long until i see the effects of prednisone for an allergic reaction to cephalexin , severe rash?

A few days: You should start seeing improvement hopefully within a few days. Using a topical steroid cream with the oral steroid can also help quicken recovery. If it is not improving, let your physician know. ...Read more

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Is there another drug combination for diverticulitis besides Flagel? I am also taking Bactrim due to allergies to Cipro, (ciprofloxacin) Keflex and Penecillin.

Is there another drug combination for diverticulitis besides Flagel? I am also taking Bactrim due to allergies to Cipro, (ciprofloxacin) Keflex and Penecillin.

Antibiotic allergies: You need the help of an ID doctor-since they are experts in antibiotics. First, I would want to 'define' ur allergies further-because sometimes a patient is labeled as 'allergic' & they aren't really allergic at all. That is really important. If ur truly allergic to penicillin, cephalosporins & cipro (ciprofloxacin) which is a fluoroquinolone, ur options are quite limited for oral therapy. Doxycycline might help. ...Read more

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My doc gave me keflex to take prior to an upcoming procedure but im alergic to penecilian (sp). Should I be concerned about a possible reaction?

My doc gave me keflex to take prior to an upcoming procedure but im alergic to penecilian (sp). Should I be concerned  about a possible reaction?

Maybe: Reportedly about 10% of penicillin-allergic patients will also be allergic to Keflex or other cephalosporins. If you develop a rash or difficulty breathing on penicillin, you should probably ask your doc for an alternative antibiotic. ...Read more

Dr. John Chiu
1,030 doctors shared insights

Allergic Reaction (Definition)

Sensitivities to substances, called allergens, that come into contact with the skin, nose, eyes, respiratory tract, and gastrointestinal tract. They can be inhaled into the ...Read more