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Wednesday, Sept. 20, 2023

World Penicillin Day

Penicillin allergies could be inaccurate

My doctor told me 40 years ago that if I took penicillin again I would die!”

“I was told not to take penicillin because my mother was allergic to penicillin.”

“I was told I cannot take cephalosporin antibiotics like Keflex because I am allergic to penicillin.”

In practice I have encountered many inaccurate, outdated and old wives’ tales about allergy to medications, but most of all to penicillin. Penicillin is the most commonly claimed drug allergy by patients. According to Dr. David Khan at the University of Texas Southwestern Medical School in Dallas, 10% of the population claims to be allergic. Over 95% of those who claim to have penicillin allergy do not have penicillin allergy and can be “de-labeled” as being allergic to penicillin. Most people labeled as allergic to penicillin were never allergic to begin with, especially for those labeled in childhood. So, to celebrate the 95th anniversary of the discovery of penicillin by Sir Alexander Fleming, the world’s first antibiotic, let’s clear the air about penicillin allergy.

There are two interesting facts that longterm studies have shown. Even if one truly had a penicillin allergic reaction, 50% of people with a true penicillin allergy lose that allergy in five years, and 80% of those will lose that allergy in 10 years. But despite those factoids, in our era of electronic medical records, this inaccurate allergy will be flagged in the chart forever unless someone takes the initiative to confirm or deny it. And who has time for that?

Actually, allergy-immunology specialists do. It is important to remove inaccurate medication allergies because this can unnecessarily restrict patients from using basic and standard-of-care medications they need. This also means they may get an inferior and more expensive substitute. And in the case of penicillin, using the new stuff may not be as effective as our 95-year-old friend penicillin. Here are a few examples of the harms of the fake penicillin allergy.

In obstetrics, Massachusetts General Hospital found women with a reported penicillin allergy were less likely to receive appropriate antibiotics and received clindamycin and vancomycin more often instead. These “big gun” antibiotics have more side effects and are less effective for premature rupture of membranes, leading to a tripling of the risk of endometritis. There was also a 10% higher rate of C-sections. Penicillins are the preferred antibiotic for Group B Strep (GBS), a common gynecological bacteria.

Regardless of the specialty, patients with penicillin allergy labels are more likely to be treated with suboptimal alternative antibiotics, have more costly health care, have more extended hospital stays, and are more likely to develop side effects and complications from the “big gun” antibiotics used like MRSA and Clostridium difficile.

So how do we in allergy-immunology remove penicillin allergy? Typically, we take a history and try remembering what occurred all those years ago. If it has been many years and the reaction was mild, we would have you take amoxicillin in the office and be observed for one and a half to two hours. If there is more concern and a more severe reaction, we can do a penicillin skin test and then do the amoxicillin test. Either way, years of misunderstanding can be cleared up in two to three hours. If you are allergic, we can also list medications that are cross-reactive and safe to take and those that are not safe today based on molecule structure.

The best way to find a fellowship-trained allergist is to check the American College of Allergy, Asthma and Immunology’s website at www.acaai.org/find-an-allergist.

Dr. Anand Bhat is a fellowship-trained allergist at Highland Clinic.


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