Is there a penicillin allergy test?

By: Michael J. Flais, MD

Michael J. Flais, MD

Penicillin allergy is the most common medication allergy, affecting up to 20% of the population by adulthood. This is unfortunate because penicillin antibiotics have a number of advantages over other types of antibiotics as they are generally more effective and better tolerated than other classes of antibiotics. Non-penicillin antibiotics may increase the likelihood of antibiotic resistance and may have increased risks of side effects or complications such as c. difficile (C Diff), a bacteria that can cause severe diarrhea. 


Most individuals who had an adverse reaction to penicillin develop what is considered a mild rash, such as hives.  Severe adverse reactions to penicillin, such as anaphylaxis, are extremely rare. Thankfully, most allergies to penicillin resolve. Of those people who experienced what is considered a mild adverse reaction while using penicillin, approximately 90% may no longer have the allergy. The likelihood of an allergy to penicillin resolving increases over time.   

At Colorado Allergy and Asthma Centers, we can help to determine if someone still has an allergy to penicillin.  Depending on the severity of the person’s reaction to penicillin, and how recent the reaction was, they may undergo allergy skin testing to penicillin, followed by an antibiotic challenge if skin testing is negative. If a person had a mild reaction to penicillin, then they will likely be considered low risk and might undergo the antibiotic challenge without the need for allergy skin testing. A penicillin challenge involves ingesting a small amount of a penicillin type antibiotic, such as amoxicillin. If the small amount is tolerated then a larger amount of the antibiotic will be given. In many cases, the challenge can be performed with only one dose of the antibiotic. 

If you or someone you know has an allergy to penicillin, schedule an appointment to determine if the penicillin allergy has resolved.    

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