Amoxicillin Allergy or Something Else

I really want to encourage younger healthcare professionals to ask questions, and realize that no matter how experienced you are, there are going to be times throughout your career where you don’t know an answer.  There will also be times where caring professionals disagree.

Case Study:

Day 1:  18 month old boy on zero medications diagnosed with a double ear infection and prescribed amoxicillin twice daily.  Received 1st dose that evening.

Day 2-7: Taking medication as prescribed with zero missed doses.  Symptoms of ear infection much improved over this period.

Day 8:  Mom notices a few spots (some about the size of a dime) all over different parts of the body.  Amoxcillin dose held and taken in for reassessment of rash and to assure ear infection has resolved.  Last dose of amoxicillin on the eve of day 7.  Diagnosis is likely amoxicillin allergy.  Ear infection appears mostly resolved so no further antibiotics warranted.  Amoxicillin discontinued.  Benadryl recommended as needed for the rash and anticipate that rash will begin resolving upon discontinuing the likely offending amoxicillin.  Minimal rash on the face.  No fever, vitals unremarkable.  Rash looks like this:

Amoxicillin Rash - baby boy

Day 9:  18 month old sleeps through the night, looking way worse in the morning with extensive spreading of the rash.  The right eye is nearly closed shut due to the soft tissue swelling around the eye.

Amoxicillin rash day 2

Amoxicillin rash day 2 belly

Due to the worsening condition, an ER visit is made with assessment of the eye and worsening rash.  Vitals, temperature are fine.  Mood, appetite, etc. all relatively normal as well.  Diagnosis is likely “classic” viral infection causing rash.  The ER doctor said there would be nearly zero doubt about the diagnosis had the patient not been on amoxicillin, but he believes it is a viral infection.

Visit to regular pediatrician that day leads to script for prednisolone.  Pediatrician was non-committal on diagnosis, but thought it was hard to ignore the amoxicillin.

Day 10 with use of diphenhydramine and prednisolone, rash is fading and much less pronounced than day 9.

I tend to believe it was an allergic reaction.  He had been numerous other kids this week, so a contagious viral infection does also have some validity.  So, what do you think?  Amoxicillin allergy or intolerance, viral infection, combination, or something else?  If you are in the camp of viral infection or something else, would you dare give amoxicillin again?

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  1. Leo M Lawless

    This child’s rash was rather severe but why treat with both prednisone and diphenhydramine? If it was allergic the diphenhydramine would not only alleviate it but also be diagnostic as to it being allergic.
    Treating again with amoxicillin in this patient would seem too risky but in patients with mild rash treating through it is often the right thing to do unless there are siblings with a history of anaphylactic reactions which then raises the risk of doing so,

    • chri1599

      Good question! – That was an error on my part and I could’ve wrote that more clearly…Diphenhydramine was used on day 8 including before bedtime and did not seem to relieve the rash as obviously it was much worse on Day 9 in the morning. Diphenhydramine was continued as needed if any itching/scratching was occurring, which that symptom never seemed to bother him, so no diphenhydramine was used following the prednisolone script from the pediatrician, hope that was clear 🙂

  2. pinadon

    No way I will give back amoxycillin, not for a while. In the case the body reacts for first time or for second time. Eyes looks like amoxicillin reaction but stomach, let me confuse. Where I live they will treat the baby with prednesol and cream. Thanks a million for the post

  3. gopinath

    I personally feel that it is amoxicillin allergic reaction. No doubt as the allergic symptoms are subsided on treating with prednisolone + Diphenhydramine. If a patient is allergic to amoxicillin , there may be a chance of getting the same with other antibiotics too. Moreover it is a common ADR sensitive reaction of the most of the antibiotics. It is better testing the patient again giving the same antibiotic with cautiously and look for the sensitive reaction. If it is positive, better to try alternative antibiotic by giving a test dose.

  4. Rob

    Tough case. The rash is classic urticaria and could be due to allergy or virus. I would advocate skin pinprick testing. >90% of documented penicillin allergy are false positives ( This is likely to due rashes as kids similar to this case. The allergy testing could rule it out and allow more appropriate antibiotic use in the future.

    As an aside, this patient probably should have had wait & see antibiotics instead:-)

    • Jody Reel

      Thank you for recommending a rechallenge via PCN skin testing. The CDC is actually recommending it in certain instances for antimicrobial stewardship. There is little chance of a severe reaction from it. Additionally, most PCN allergies last 5-7 years, so I would recommend retesting after that if the first is positive.

  5. Tiffany

    I think we should not over look biphasic allergic reaction as well. I do not feel that it would be appropriate for anyone but an allergist to evaluate this child’s potential allergy; his reaction was too severe to risk anaphylaxis with subsequent doses.

  6. melissa

    It’s a possibility that you are dealing with both a virus and allergy which is why the reaction is so severe. Typically a reaction is seen by day 3 to 4 which is why this is so odd. The absence of any face symptoms at first was puzzling. Response to prednisone clearly states some kind of inflammatory reaponse. This kid doesn’t get amoxicillin back until seen by an allergist who isn’t usually going to see them until they are 2. I guess omnicef and azithro are your new friends.

  7. Chad

    This isn’t at all the classic -cillin or drug food rash. This plus the center discoloration indicates viral/infectious. ER docs see amazing amounts of skin problems and are often more of a peds expert than an actual pediatrician. If the next C&S comes back indicating a -cillin, I’d dispense it with confidence. Unlikely, tho, given increasing amox resistance out there.

  8. Jessica

    I discovered this while googling and while I am not I doctor, my then 13 month old daughter had a similar reaction to this, if not more severe and we are also still stumped as to whether it was actually an allergic reaction. It started on day 7 of amoxicillan with your class allergic reaction rash. Pedi saw her and confirmed. She slept all night and woke up serverly swollen. Within an hour she started developing larger spots similar to the boy in these photos, but by the time we got to the ER she looked like she had been beaten with a bat because blood vessels under her skin began to burst creating bruises all over her body. The first doctors we saw thought virus, then the derm on call (even though there was no raised rash) finally made the call and said amox reaction. No one is very confident with the diagnosis because it was so atypical. She was treated with 3 days of prednisone. I found this page because I am trying to read about links to allergic reactions among siblings. I have a 6 month old suffering from chronic ear infections and have avoided amoxicillan out of fear. I’m not sure we can keep avoiding it though because no other drugs seem to kick it.

  9. Emma

    I actually had this exact scenario this week with my daughter! Except the feared allergic reaction was really scarlet fever. Totally differect rash presentation, non-itchy, pinpoint, sandpapery rash instead of classic urticaria,which should have clued me in. When it’s my own kiddo, though, I always get a second opinion! And she’s still on her amoxicillin,without problems.

    • Eric Christianson

      Crazy…always that much more scary when its your own!

  10. Michelle Z

    My son finished amoxicillin day 10. First noticed a very fat lip. Then noticed what looked similar to a mosquito bite. The lip increased in size while eating his breakfast. Called the doctor got an appointment and less than an hour later feet had rash and swelling. Saw Doctors and was told 5ml benedryl twice a day. Did that, oatmeal bath and a hydrocortisone rub down. Fell asleep and woke screaming and scratching. An additional dose of benedryl and another hydrocortisone rub down. Day 11, bottom lip down, top lip swelled to the point of no creases, both feet and hands swollen, rash is raised and circular is the most prominent pattern. Called doctor and they phoned in prednisone. Within 4 hours raised rash was almost flat, turned sort of grey in the middle of the red and pink outlines. Swelling better in feet but can still not wear shoes.
    This is the second time he has had amoxicillin in his life (almost 3). The first he did have this but much more minor and was said to be viral. Now has it as an allergy on his record.
    Have pictures to document these 2 days and post treatment.

  11. Dominique

    This child’s rash looks exactly like my son’s rash on day 9 of a 10-day course of amoxicillin at the age of 15 months. Rash came on slowly over 24 hours but was eventually accompanied by facial swelling and swelling of the hands and feet. Was treated with Benadryl then on day 10 with prednisone in the ER. The rash flattened, darkened, and faded to purplish grey then took a couple of days to disappear. We were told amoxicillin allergy then and I would not be comfortable administering it unless we had a negative allergy test.

  12. Jess

    My son had same rash and swelling after being on amoxicillin for 7 days. Our pediatrician is calling it Serum Sickness – severe allergic reaction to amoxicillin.

  13. Neelum

    I think it is amoxcillin allergy. It may not be text book correct but the timing indicates it to be amoxcillin rash. Further more human biology is complex. Amoxcillin big broad spectrum it might have killed some other microbe off whose dead bodies caused the immune system to react in this way or it may be reaction to sulphur group in amoxcillin itself. I would be hesitant in giving the baby amoxcillin or other pencillins unless there is no option left.

  14. Stephanie

    My son had the same reaction after the 9th day of taking Amoxcillin he started with a small rash the next day more patches appeared by early the next morning his body was covered in hives and welts. My sons feet, hands, eyes, ears were all swollen. Took him to his pedia dr. Started the steriod the rash flattened and started going away.
    I would include pictures but not sure how to attach them to this forum.

  15. Jackie

    3 of my 4 children had this same rash on amoxicillin along with joint swelling.All three occurred on day 7/8 on the antibiotic and was the second time they had been on it. Benadryl had no effect on the rash. My first son had no medication and it cleared in 4-5 days. My second son had been given a steroid and it cleared it within two days. My oldest son has been on amoxicillin three times since with no reactions.


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Written By Eric Christianson

October 29, 2014

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