March 23rd, 2009
03:24 PM ET

Am I really allergic to penicillin?

By Miriam Falco
CNN Medical News Managing Editor

About 20 years ago, when I was barely out of college and a struggling journalist, I developed a horrible sore throat. I didn't have a regular doctor, so I had my throat examined in a small clinic in a strip mall. The doctor figured I had strep throat, but the test came back negative. Still, she prescribed antibiotics and sent me on my way. The next morning, I woke up with little red dots all over my body, so I went back to the clinic. The same doc looked at me, said I had hives, harrumpfed that I was allergic to penicillin and gave me a prescription for a different antibiotic. The sore throat eventually went away, but every time since that I've gone to a doctor or dentist and I’ve listed penicillin as one of my allergies. Still, I always wondered if I really had an allergy; I took penicillin frequently during my childhood and never had an allergic reaction.

I came across a recent study published in the Annals of Emergency Medicine that said 80 to 90 percent of people who report being allergic to penicillin are really not.

This new study sought to determine how many patients who came into an Emergency Department (ED) and said they are allergic to penicillin really were allergic. Using two back-to-back skin tests, doctors in the ED at the University of Cincinnati tested 150 patients who reported having a penicillin allergy. 91 percent of these patients tested negative for the allergy.

For Dr. Joseph Moellman, an associate professor at the University of Cincinnati Department of Emergency Medicine, who conducted this study, finding out that taking the additional 30 minutes to conduct these two tests has several important implications. "We see a lot of patients with pneumonia, with sepsis, for which penicillin is a great drug...It's also a lot cheaper." Moellman says the average cost saving is $71. So if, for example, a pneumonia patient is in the hospital for a week, and possibly needs antibiotics every six hours – significant savings can add up very quickly. Plus, using penicillin where it's known to work allows doctors to save the few newer antibiotics we have for illnesses that have become resistant to penicillin.

"This is good information," says Dr. Clifford Bassett, an allergy expert and spokesperson for the American Academy for Allergy, Asthma and Immunology. "The fact that the test is fast and inexpensive is helpful." But he did point out that there has been a shortage of proper testing agents for penicillin. Once these testing agents become more widely available again, Bassett says that this test could be done in other settings too, not just in an emergency room, but also in a regular doctor's practice.

He adds that some previous research suggests that some people who genuinely were allergic to penicillin could lose their allergy if they don't come in contact with this drug for 10 years or more.

Of course neither doctor could explain whether I really am allergic to penicillin. But Moellman explained that sometimes a virus itself can cause hives, and Bassett told me that usually it takes more than 24 hours for a penicillin allergy to become evident. I, for one, plan to get tested to determine whether I truly am allergic to penicillin.

Have you been told you're allergic to penicillin? Would you consider getting tested?

Editor's Note: Medical news is a popular but sensitive subject rooted in science. We receive many comments on this blog each day; not all are posted. Our hope is that much will be learned from the sharing of useful information and personal experiences based on the medical and health topics of the blog. We encourage you to focus your comments on those medical and health topics and we appreciate your input. Thank you for your participation.

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soundoff (46 Responses)
  1. Michael Stanley French

    I took penicillin in my late teens and my hip swelled up as big as a basketball and was so tight I could not bend over. I was told that I was allergic to it and I have listed that on all of my medical papers all these years. I am now 58 and am wondering if I really am allergic or was all these years. Yes I would consider getting tested. Please tell me what do I ask my doctor how to proceed with this.

    March 23, 2009 at 18:53 | Report abuse | Reply
  2. Nancy

    When I was around 6 yrs old I was given penicillin and sulpha
    and went into shock. Later when I was in my 30's I went into shock
    with hydrodiuril (contains sulpha)- one pill only. Not going to test out if it is penicillin or not when I was a child. Too risky.

    March 24, 2009 at 06:50 | Report abuse | Reply
  3. Ohio Betty

    When I was 9, I had to take liquid penicillin over a long period of time ("long" in kid terms ... maybe a couple months??) because of a bout of pneumonia.

    One afternoon, I broke out in a terrible case of hives, which our pediatrician attributed to the penicillin. He said my body had developed an intolerance to it, and I shouldn't have penicillin again.

    That was 36 years ago. I'd love to be tested to see if I'm allergic now.

    I haven't been on an antibiotic since some sinus surgery four years ago, but it would be nice to know I could use penicillin for exactly the reasons mentioned (cost and preserving other antibiotics for penicillin-resistant problems).

    March 24, 2009 at 11:08 | Report abuse | Reply
  4. Judy Griffing

    I have been told that I am allergic to penicillin. I would like to get tested but I don't know where to go.

    March 24, 2009 at 11:11 | Report abuse | Reply
  5. DB

    I've been diagnosed as being allergic to sulfa. Unfortunately, that allergy is probably real, since I felt gradually worse for days after taking the medication twice in four years for an infection. At a week after the medication was started the second time, I was feverish, fatigued, and only then just beginning to show a petiechiae style rash all over the body. My eosinophil count (normally between 0 and 3 %) was 13.4%. I'd be willing to be skin tested to see if it's still an active allergy.

    On the other hand, I worked with a lot of patients when I was in an ED. Conversations often went like this:

    Me "Are you allergic to any medications?"

    Patient "Yes, antibiotic X"

    "What happens when you take antibiotic X?"

    "I get stomach cramps and bad diarrhea."

    "Umm...that's not an allergy, that's an unpleasant side effect."

    A lot of patients don't know the difference between allergies and side effects, and those fine-print inserts only help a little and take a long time to read.

    March 24, 2009 at 12:32 | Report abuse | Reply
  6. Andrew

    Was always told I was allergic to pennicillin since day 1. I have a heart murmur that I needed to take special antibotics for every dentist appointment. I recently went and got tested (22 years after being told I will always be allergic) and no allergy whatsoever. This included 2 skin tests, 2 injections and a 10 day oral challenge. The allergist is prepared for an emergency and it is in a controlled environment. Total visits cost : $120 + $70 for the meds. Worth it so I can now use penicillin instead of overly expensive other antibiotics.

    March 25, 2009 at 13:28 | Report abuse | Reply
  7. JD

    I desperately need to be tested since I have a strong family history of severe penicillin allergy (close family member goes into anaphylactic shock if exposed). My pediatrician would not prescribe it to me for this reason. It would be nice to know if I could use it, if needed. Much cheaper than any of the alternatives.

    March 25, 2009 at 16:55 | Report abuse | Reply
  8. Nicole

    When I was 5 or 6 I had terrible recurring bouts of ear infections. They always put my on the pink liquid Amoxi-drops (Amoxicillin). After a few years I never had the problem (or amoxicillin) again. Then in college I ended up with some chest infection and since I was definitely allergic to sulfu they put me on Amoxicillin. After about the 6th day I broke out in the biggest hives I have ever seen. They were inside my mouth, in my ears, everywhere. Drs told me that I had developed an intollerance from the heavy doses during my childhood. I have not actually had plain old penecillin, but I was advised to stay a way from any of the -cillin drugs.

    March 27, 2009 at 12:42 | Report abuse | Reply
  9. Dolly Rickerman

    My 10 year old son, who has had amoxicillin before, broke out in hives on his 9th day of treatment (the 10th day was his last day to get the medicine). He was being treated for a sinus infection. His pediatrician said that he had an allergic reaction to the amoxicllin and that he should never be given any penicillin. He wants my son to be tested again in a year with a full allergy test...why does he have to wait a whole year?

    April 1, 2009 at 22:10 | Report abuse | Reply
  10. Julianne

    I am currently fourteen-years-old.

    Two years ago had severe allergy to something. My doctor percribed me amoxicillin. A few minutes after taking the first dose, I broke out in hives. My dad (a paramedic, and has a nurses degree), said that maybe I was allergic to the medicine. So, I took it a second time. Again, I got hives. He said I was allergic and my parents have written it in for things I am allergic to on forms and such.

    April 3, 2009 at 14:37 | Report abuse | Reply
  11. Theresa

    Several years ago I went to the doctor and was prescribed pencillian, I started to get better during the 10 day regimen. However about day 7 I started having extreme joint pain I could barely move, day 8 I broke out in a rash all over on day 9 I called the pharmacists to see if these new symptoms were an allergic reaction, he said yes to stop taking the medicine (I had one day left). Since that epsiode I have always told my doctor that I am allergic to penicillian but recently when visiting the doctor for an ear infection I was asked how long it had been since I tried pencillian, I wondered why the on-call doc asked me, I see the answer from this arrticle. I could not remember but I think it has been more than 10 years ago. I will have the office visit test done soon to double check!

    April 3, 2009 at 17:26 | Report abuse | Reply
    • crescenza2

      Theresa, because you had extreme joint pain, this sounds like a serum sickness type of reaction which is not a normal penicillin allergy. You need to speak to an allergist and find out if you can ever take penicillin again, regardless of what a skin test says. Serum sickness type reactions are not the same as allergies.

      November 10, 2015 at 11:26 | Report abuse |
  12. Sharon

    I have been considered allergic to penniclin since I was between 6-8. I had massive ear infections in which I would be going to the ER every week (stupid military doctors wouldn't let get tubes in my ears, as I am still plauged with them today) I remember always getting sick immeaditly after taking the meds (and it was liquid pennicilin and amoxicilin as well) today I am now allegric to all antibotics to a point to where I have bad spasms and my throat will start to swell, so no I have no plans to get retested...to scary to think about (I will just stick with the on sulfa drug that does work...yes the side effects are bad, but not near as bad as being violently ill and feeling like I cant breathe)

    April 9, 2009 at 05:28 | Report abuse | Reply
  13. negmyblog

    At around age 3 my son was given pennicilin for some infection. Within a few hours he developed hives...We took him to the ER and we were asked what he had taken...with that, they decided he was allergic to pennicilin.

    About a year later we moved out of the US. My son got sick and the pediatrician (an old man...) prescribed him pennicilin...When we realized what he had done, we called him immediately and argued with him that we were told and had already told him that my son was allergic...His response? "I'm the doctor, so just give him the medicine I gave you...he'll be fine..." Slightly frightened we gave him his "pennicilin" terrified that something would go wrong...NOTHING DID...Our old pediatrician doctor obviously knew much more than the other doctors we had previously seen.

    To this day when asked I always tell the doctors he is allergic to pennicilin ONLY because in the US there are so many restrictions on parents from Child Protective Services...that we worry that if we don't tell the doctors and something does go wrong, some CPS agent will call us negligent and take our child away...Do we believe he is allergic at this point? Not really...Our old doctor out of the country obviously knew well...

    I would love to have my child tested.

    April 14, 2009 at 06:00 | Report abuse | Reply
  14. Tim

    I have also been told that I am allergic to penicillin since I was a pre-teen. I am now almost 41 and would love to be tested. I had to see an on call Dr recently who asked me how I knew I was allergic to penicillin. He then proceeded to tell me that same thing that a lot of people have been told that they are allergic and are really not.

    April 16, 2009 at 11:42 | Report abuse | Reply
  15. Kathy

    I have had allergies to food andf medicine since I was in my 30's. Once when I was in the hospital the doctor gave me penicillin knowing I was allergic to it. I had a wrist band with the info as well as on my chart, I was give the penicillin and after that I blew up with hives and my lips were swollen. Thank GOD I was in the hospital at that time so they gave me medicine to counter react the penicillin immediately . It was not a good expericence..After about 15 years, I tried Ceftin, which has penicillin in it, and I had no reaction. So I do wonder if this is true that after ten years it is ok. I am also HIGHLY allergic to SHELLFISH, which I am not ready to try and find out if I am still allergic. This allery to Shellfish almost kiled me. I have been recently tested for allergies and it's a never ending saga of when do these allergies pass, so I don't have to be so afraid of what can happen if I do eat or receive medicine that I am allergic to.

    April 21, 2009 at 10:05 | Report abuse | Reply
  16. Elizabeth

    I have a 3 year old son. On his first birthday, he aquired some terrible flu, with a temp of 105 that I could not get to stay down. His pediatrican prescribed penicillin, and just after his first dose, broke out in red dots (hives?) which began on the bottom of his feet and began to spread up his legs. Doctor said he was allergic to penicillin, but I would be interested in testing him to know for sure, as long as there were no negative effects from the testing.

    April 27, 2009 at 21:30 | Report abuse | Reply
  17. Yellow

    I've been told I was allergic to penicillin from birth, but at this time they were not sure I was allergic to penicillin or if it was the other medication I was taking. I was always ill as a child and penicillin was the one thing that was never an option for me just because of my mothers fear of me being allergic to it. At the age of 2 or 3; not to sure on the age, I became very ill, and my normally doctor was not able to see me. The other physician I was told to see gave me a very low dosage of penicillin even though on my medical chart it states I was allergic to it. Instead of getting better I became more ill and broke out in a large rash. The rash covered me from head to toe and my mother didn’t know what to do. She took me to emergency and explain to them what I had been given and what had happen. I remember her telling me that the doctors in emergency told her if she knew I was allergic why did she let the doctor give it to me and even to this day she does not know, but after this incident she made sure to make a note of telling the doctors over and over about my reaction to it. To this day I still have to state that I am allergic to penicillin, but because a lot of things I was allergic to as a child my reactions are not as bad as an adult I think I would consider being tested only if my doctor thinks it’s best, other than that I’ve gotten this far in life with out having to have any form of a penicillin dosage so I think I should be fine if I never do.

    May 25, 2009 at 20:12 | Report abuse | Reply
  18. Highly allergic

    Yes, some people are deathly allergic to penicillin. I am 53 years old today. When about 10 years old, I took the medicine in pill form. Two days later the reaction started. It lasted for about 7 to 8 weeks. Basically I had severe swelling in the form of a welt that covered my entire body for that duration. The itch could never be satisfied as its in your blood. I sat around for days & weeks with ice packs all over my body, couldn't sleep, taking drugs like benadryl every 4 hours, about 10 pills at a clip. After a couple weeks I gradually lowered the benadryl dosage by 1 pill a week. As an adult, my sister had a drug, amoxcillin, and reacted worse than me. She too was highly allergic though she had taken the drug as a child. She swelled so badly, that she actually became paralyzed–the blood gets into the bones and eventually the joints. The joints swelled so badly she became paralyzed and hospitalized for weeks. This is not a drug to mess around with if you might have an allergy to it.....

    May 28, 2009 at 18:35 | Report abuse | Reply
  19. Laurie

    I was tested at Kaiser Permanente several years ago and am happy to report that I am Not allergic to penicillin. I still have not taken it to really know if it is OK to take. If you have ever been told that you are allergic to Penicillin, you should get tested as it opens up a whole group of medications available. I hope that the scientists find ways to test other drugs as I'm allergic to several antibiotics.


    June 6, 2009 at 11:26 | Report abuse | Reply
  20. Margie

    In my 30s, mainly, I got a lot of colds, sinusitis, etc. I often got a few red bumps, mainly on my inner arm, after taking antibiotics. I thought they were hives. When I reported this to the prescribing doctors (or pharmacists, if the doctor's office was closed), they told me to stop taking it and try something else. I had this reaction to Ceclor (cephalosporins), sulpha, and penicillin (or penicillin-related drugs). I also ended up in the hospital with severe diarrhea and horrible stomach cramps from Augmentin (which some say was a side effect and some say was an allergic reaction).

    At any rate, one doctor asked me to see a dermatologist and get tested. The only test they had for these antibiotics was for penicillin. I had the skin test in his office and, to my surprise, tested positive - and I only had a few hives!!! I was surprised because I thought I probably had been overcautious when I reported a few red bumps to the doctor. At that time, I took warnings to patients about side effects pretty literally (the patient info. included with the medicine), although, like in these cases, I felt I was being overly cautious. BOTTOM LINE: What the pharmacists and doctors generally told me seemed more believable AFTER I TESTED POSITIVE FOR A PENICILLIN ALLERGY. What they always said was that AN ALLERGY THAT MANIFESTS IN A FEW HIVES ONE TIME MIGHT MANIFEST IN AN ANAPHALACTIC (sp.?) REACTION (POTENTIALLY LIFE-THREATENING OR FATAL) ANOTHER TIME.


    June 16, 2009 at 21:45 | Report abuse | Reply
  21. Jerry

    So what if I'm allergic to PCN? There are enough other options that it doesn't matter one bit.

    July 31, 2009 at 16:31 | Report abuse | Reply
  22. Robert Austin, TX

    Similar to the author, I was given Polycillin at a University Health Center
    in the early 1970's, and when I developed a dotted rash on my forearms
    a few days later, the physician told me the rash confirmed I was allergic, discontinued the medication and told me to never take Polycillin nor
    Penicillin again. I followed his advice, and would love to be tested these some 35 years later to find out if I am actually (still) allergic to this useful and practical family of drugs.

    August 13, 2009 at 05:22 | Report abuse | Reply
  23. sarah jones

    i am allergic to penicillin.. waht other type of medication can i take?

    August 18, 2009 at 18:43 | Report abuse | Reply
  24. Jean

    Yes, I would consider being tested. I developed an allergic reaction to Penicillin in 2006 and have since added Amoxicillin, Clindamycin and Bactrim to the list, having reacted to each of those. I am concerned that I am running out of antibiotics to take in the event of a serious health issue.

    August 25, 2009 at 14:46 | Report abuse | Reply
  25. georgie

    I had Penicillin after having my Appendics out at 11, I had a severe reaction to it that made my throat swell and stopped me breathing. Since then I have always listed all medical docs saying that im allergic. I'm 44 now and have never had it until a doctor (not my normal Dr.) has just prescribed Amoxicllin for a sinus infection, which after reading the leaflet has Penicillin in it, I have already taken a tablet, so i'm having to check to see if I have a reaction!

    March 16, 2010 at 06:53 | Report abuse | Reply
  26. Geneva

    I was given piperacillin-bactam Iv on the 5th day I had a red area under breast . area with itching. I was given 40 mg solu medrol every 8 hours for 9 tines then skipped a day and given 3 more 40mg doses iv. Did I have an allergic reaction or was it caused by something else. Now they won't give me anything with penicillin. I have taken penicillin for 63 years and no problem

    April 7, 2010 at 18:10 | Report abuse | Reply
  27. Theresa Pierce

    As an infant I was sick chronically with ear infection and Toncilitis. Penicillin was used to treat. I broke out in hives so they used tetracycline. So I went through my 45 year telling my doctors that I was allergic to Penicillin. Just resently, through allergy testing, penicillin was NOT one of the things that showed as something that I was allergic to. I am going to sit down with my doctor and discuss what to do from here. Thank you sooo much for your article. It helps alot!!

    April 27, 2010 at 10:13 | Report abuse | Reply
  28. ML Boland

    I took Augmentin for 3 weeks due to a stubborn sinus infection. 8 days after finishing the medication, a rash developed all over my body. I saw the doctor the next day, who gave me a cortisone shot and prednisone tablets, and said I am allergic to penicillin. Can a rash develop 8 days after stopping the medication? Am I really allergic to penicillin?

    May 1, 2010 at 20:20 | Report abuse | Reply
  29. Formica Sheets 

    i suffer from sinusitis and there is no permanent cure for this disease"*'

    October 20, 2010 at 06:41 | Report abuse | Reply
  30. Electric Oven ·

    i really hate sinusitis, the feeling of having a stuffy nose and headache is really annoying '

    November 9, 2010 at 15:16 | Report abuse | Reply
  31. aj

    So as a new born doctors said i was allergic to Penicillin and Sulfa. My mom said my feet turned blue and purple. But I have been taking Amoxicillin and had no reaction... hmm

    February 22, 2011 at 14:55 | Report abuse | Reply
  32. Lesa Ruddell

    I :love: this! I cant begin to describe the detail and care that must have went into this. This is a big 🙂 in my books!

    September 9, 2011 at 16:53 | Report abuse | Reply
  33. Guillermina Aholt

    Hey, this is a Great read. I have undersood this sort of perspective, previous to this and you are excellent. I really like what you have articulated here, really like what you are stating and the way in which you say it. You make it enjoyable and you still care to keep it smart. I cant wait to read more in the future from you. This is actually a terrific web site. Keep up the beautiful work.

    September 21, 2011 at 00:02 | Report abuse | Reply
  34. Carrol Amy

    I wish half of the bloggers on the internet had your writing ability and willingness to provide value to us visitors! Just fantastic, and thank you! A+

    February 6, 2012 at 10:05 | Report abuse | Reply
  35. Kori

    It is a big deal. I'm allergic to every antibiotic that comes in pill form at this time. They are doing a test at my new allergist today to see if I'm truely allergic. Otherwise, I will have to be given IV antibiotics from now on. That will be fun.

    February 16, 2012 at 00:57 | Report abuse | Reply
  36. Jennifer

    My story is almost the same! Had no problem taking penicillin as a child and hadn't really needed to take it as an adult until I had a really bad sore throat in my 30's. Went to a jack-in-the-box-doc, tested for step and came back negative, prescribed amoxicillin anyway and 3 days later hives on my mid section that spread to the rest of my body shortly after. I always wondered if I too was REALLY allergic to penicillin as well.

    This past week my daughter just got treated for asthma at the hospital. They put her on amoxicillin (among other meds) and they wanted her to keep going and finish them up at home. I was being REALLY careful, using gloves and washing my hands...but I guess not good enough as the hives are back! So, I think I have my answer as I've never had hives other than these two instances. I just hope they go away faster than the last time! Last time I had them up to 5 weeks!!!

    February 21, 2012 at 23:09 | Report abuse | Reply
  37. Alvaro Zumot

    Most people will have some problem with allergies or allergic reactions at some point in their lives. Allergic reactions can range from mild and annoying to sudden and life-threatening. Most allergic reactions are mild, and home treatment can relieve many of the symptoms. An allergic reaction is more serious when severe allergic reaction (anaphylaxis) occurs, when allergies cause other problems (such as nosebleeds, ear problems, wheezing, or coughing), or when home treatment doesn't help.

    June 7, 2013 at 01:50 | Report abuse | Reply
  38. Jen

    Diagnosed with a penicillin allergy at age 10. Tongue swelled. Took a penicillin test last week at an allergist. Now age 35. Test was negative. I can now take penicillin with no reaction.

    July 16, 2015 at 02:21 | Report abuse | Reply
    • crescenza2

      Did they give you an oral challenge as well as a skin test. Usually they will give you one pill in the office to see if you react right away. Also, they want you to report if you get any type of rash within the next few weeks after taking the pill (delayed reaction).

      November 10, 2015 at 11:29 | Report abuse |
  39. Trish

    I definitely know my 4 year old is allergic to it as she goes into anaphylactic shock and even becomes unconscious and non responsive and my doctors are well aware of this as she is red flagged on the system but yet just the other day my doctor prescribes her an antibiotic but I was told not to get it until she started really complaining of a sore ear, so I went and looked it up and it was a different name instead of putting keflex doc probs didn't think I would look it up or question it but I can tell you when I found out it was penicillin based I was furious as even trying it with her isn't a chance I am willing to take

    August 4, 2015 at 02:50 | Report abuse | Reply
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  43. Ney

    Alergia à penicilina é muito grave e serio. Adorei esta materia e parabenizo ao blog por tê-la publicado.

    January 27, 2020 at 14:07 | Report abuse | Reply

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