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Penicillin/Amoxicillin Allergy

Penicillin and amoxicillin are important medicines that treat infections caused by bacteria (germs). Many people are thought to have an allergy to penicillin/amoxicillin, but once tested, less than 1% of people are truly allergic to penicillin/amoxicillin.

If your child is not allergic to penicillin/amoxicillin and they do not take these medicines because of a suspected allergy, it can lead to more problems.

What is a penicillin/amoxicillin allergy?

A penicillin/amoxicillin allergy is a serious reaction caused by your body to the antibiotic medicine penicillin or amoxicillin.

What are signs of a penicillin/amoxicillin allergy?

A serious allergic reaction can happen within minutes, or within 24 hours, and include:

  • Hives
  • Itching
  • Fever
  • Swelling of face, tongue, or body
  • Shortness of breath or wheezing
  • “Anaphylaxis”: Low blood pressure, loss of consciousness, seizure, trouble breathing, feeling dizzy or light-headed

Other serious forms of penicillin/amoxicillin allergy can take longer to happen, such as:

  • Stevens-Johnson syndrome: eye redness, mouth sores, blistering and peeling of skin
  • Serum sickness: fever, joint pain and swelling, rash, nausea
  • Liver or kidney injury (conditions called “DRESS” or nephritis)

Why is it important to know if my child has a true penicillin/amoxicillin allergy?

Penicillin/amoxicillin are the best and safest treatment for many infections. For people who have, or think they have, an allergy to penicillin/amoxicillin, they will need to take different types of antibiotic medicines (compared to penicillin/amoxicillin). Antibiotic medicines other than penicillin/amoxicillin:

  • May not treat the infection as well as penicillin/amoxicillin
  • May have more harmful side-effects on the body compared to penicillin/amoxicillin
  • May make other medicines used to treat bacteria less effective
  • May cost more
  • May lead to longer hospital stays

Are all reactions after antibiotic medicines due to allergies?

No. Penicillin/amoxicillin and other antibiotic medicines can cause common side effects, such as:

  • Headache
  • Mild nausea
  • Diarrhea
  • Vaginal itching

If penicillin/amoxicillin is given to treat an infection (such as an ear infection) while the child also has a particular virus, it can lead to a spotty rash one week or more after starting the antibiotic medicine. Because this type of rash does not happen without the virus, it is not considered an allergy to the antibiotic medicine. So penicillin/amoxicillin can be given to the child safely in the future.

Should my child be considered allergic to penicillin/amoxicillin if they have a family member with an allergy to penicillin/amoxicillin or other antibiotic medicines?

No. Allergies to medications are not genetic and do not “run in the family”. Having a family member with an allergy to penicillin/amoxicillin or other antibiotic medicines is not a reason to think your child also has an allergy to penicillin/amoxicillin.

How can I know if my child is truly allergic to penicillin/amoxicillin?

Talk to your child’s healthcare provider about their penicillin/amoxicillin allergy history. If the provider thinks there is low risk for allergy, your child can be tested with an oral challenge. An oral challenge is when your child is watched closely in the hospital or clinic to see if a reaction happens after giving them amoxicillin by mouth.

If your child is at high risk, an allergist (doctor specializing in allergies) will need to review more with you and your child. They may do a skin test and/or an oral challenge. The allergist may then decide to give penicillin/amoxicillin to your child.

If my child is truly allergic to penicillin/amoxicillin, what can be done?

  • Your provider will prescribe another type of antibiotic medicine to treat your child’s infection.
  • If a penicillin antibiotic medicine is needed, an allergist can give it gradually in the hospital under close supervision (“desensitization”).
  • Have your child wear a medical alert necklace or bracelet, in case they or you are not able to tell a healthcare provider that they have a penicillin/amoxicillin allergy.
  • As many as 80% of people with a true penicillin/amoxicillin allergy can outgrow it by 10 years after their last antibiotic medicine reaction. An allergist should be consulted if considering penicillin/amoxicillin in an older child or teenager who had an allergy identified earlier in life.


This information is not specific to your child but provides general information. If you have any questions, please talk further with your child’s inpatient doctor.

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This page is not specific to your child, but provides general information on the topic above. If you have any questions, please call your clinic. For more reading material about this and other health topics, please call or visit Children's Minnesota Family Resource Center library, or visit

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