If I polled a room today and asked how many individuals were allergic to penicillin or one of its siblings – such as amoxicillin – up to a quarter of those people would raise their hands. You may even be one of them. But have you ever wondered if that was true?

September 28 is National Penicillin Allergy Day, which celebrates the day Alexander Flemming discovered penicillin in 1928. The discovery of penicillin was so significant that it merited a Nobel Prize in 1945, and it’s no exaggeration that penicillin has save millions of lives.

More people report an allergy to penicillin than any other drug – up to 25 percent of the population. However, up to one-third of those individuals are unable to pinpoint their specific reactions, which isn’t surprising, considering as many as 75 percent of those reported reactions happened before they were 3 years old.

Many reported reactions – such as headache, diarrhea or even a family member with penicillin allergy – aren’t even the result of true penicillin allergies. Rash is the most commonly reported reaction, but it can be difficult to differentiate between rashes caused by an allergy or those caused by viruses, which are extremely common in young children.

So what’s the big deal? The solution seems simple: Avoid penicillin and we’ll be fine, right? Not exactly. The antibiotics used in place of penicillin are often less effective than penicillin antibiotics and carry a higher chance of infections such as Clostridium difficile, a serious diarrheal illness that can require hospitalization.

On top of that, the allergy is associated with longer hospital stays as well as drug-resistant bacterial infections such as methicillin resistant Staphylococcus aureus (MRSA) and vancomycin resistant Enterococcus (VRE), which can be difficult to treat.

What allergy  ‘challenges’ reveal

Up to this point in the article, you may have noticed that I use the term “reported allergy” instead of “allergy.” I do this because less than 5 percent of people who report penicillin allergies would truly be allergic if tested.

The American Academy of Allergy, Asthma & Immunology and the American College of Allergy, Asthma & Immunology recommend actively challenging reported penicillin allergies.

These testing “challenges” can range from simply discussing reported reactions to skin pricks– in which a qualified physician injects a small amount of penicillin or one of its derivatives in the top layer of skin and looks for a reaction. Another challenge involves administering a dose of a penicillin to gauge a true reaction. All this testing can be performed safely, in an office setting safely. Less than 4 percent of individuals challenged have had reactions – usually mild ones such as a rash – with no reports of serious reactions, such as anaphylaxis.

Those who experience true reactions to penicillin can benefit from challenging. After five years, up to 50 percent will no longer be allergic to penicillin on testing, and this number increases to 80 percent after 10 years.

Challenging a reported penicillin allergy is well worth it, with some patients reporting savings of nearly $2,000 per person, per year, in healthcare costs.

Ask your physician or healthcare provider about your penicillin allergy and see if you would benefit from a direct challenge or referral to a board certified allergist. Freeman Health System is proud to be the region’s only hospital offering penicillin challenges for low-risk hospitalized patients.

References

Castells M, Khan DA, Phillips EJ. Penicillin allergy. N Engl J Med. 2019;381(24):2338-2351.
National Penicillin Allergy Day. NPAD. Published June 28, 2017. Accessed September 25, 2024. https://nationalpenicillinallergyday.com/

Stone CA Jr, Trubiano J, Coleman DT, Rukasin CRF, Phillips EJ. The challenge of de-labeling penicillin allergy. Allergy. 2020;75(2):273-288.

Macy E, Contreras R. Health care use and serious infection prevalence associated with penicillin “allergy” in hospitalized patients: A cohort study. J Allergy Clin Immunol. 2014;133(3):790-796.

Khan DA, Banerji A, Blumenthal KG, et al. Drug allergy: A 2022 practice parameter update. J Allergy Clin Immunol. 2022;150(6):1333-1393.

Cooper L, Harbour J, Sneddon J, Seaton RA. Safety and efficacy of de-labelling penicillin allergy in adults using direct oral challenge: a systematic review. JAC Antimicrob Resist. 2021;3(1):dlaa123.

Sullivan TJ, Wedner HJ, Shatz GS, Yecies LD, Parker CW. Skin testing to detect penicillin allergy. J Allergy Clin Immunol. 1981;68(3):171-180.

Blanca M, Torres MJ, García JJ, et al. Natural evolution of skin test sensitivity in patients allergic to beta-lactam antibiotics. J Allergy Clin Immunol. 1999;103(5 Pt 1):918-924.