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Are You Really Allergic to Penicillin?

If you are allergic to penicillin, you’re not alone. Penicillin allergy is the most common drug allergy in the US, affecting 10 percent of the population. That percentage is even higher in the patient population with estimates of around 25 percent of inpatients having a penicillin allergy on their medical record.

“Even though you might have a penicillin allergy on your record, you may not actually be allergic to penicillin. Over 90 percent of people who have a listed penicillin allergy, when tested and challenged, do not have that allergy,” says Dr. Paige G. Wickner, MD, MPH, of the Division of Rheumatology, Immunology and Allergy at Brigham and Women’s Hospital (BWH).

Common Causes of a False Penicillin Allergy

The large number of inaccurate penicillin allergy listings is high for many reasons. One common cause of an erroneous listing is if a patient took penicillin during a childhood illness and a rash appeared. Even though the rash may be unrelated, the child would still have a penicillin allergy added to their record. Additionally, penicillin allergies may disappear over time. The risk of an allergic reaction to a penicillin allergy decreases at a rate of 10 percent a year.

Many patients may need penicillin or a related medication as treatment, but they can’t receive it due to a listed penicillin allergy. 

“The large number of patients with a listed penicillin allergy is problematic to patients and providers for many reasons,” says Dr. Wickner. “Many patients may need penicillin or a related medication as treatment, but they can’t receive it due to a listed penicillin allergy. This can result in increased morbidity, increased lengths of hospital stay, non-first-line antibiotic treatment, and higher costs to patients and the healthcare system.”

What Should You Do If You Think Your Penicillin Allergy is Wrong

“We encourage patients to see an allergy specialist to clarify their penicillin allergy. It’s best for a patient to have testing in an outpatient setting when they are feeling healthy rather than in an inpatient setting,” says Dr. Wickner.  

You may visit an allergy specialist at BWH through the Immunology and Allergy Services. You can request a referral from your primary care physician. Allergy specialists can perform a penicillin skin test and/or challenge to determine whether you have a penicillin allergy. Healthy outpatients can expect the appointment to take approximately two hours.

If the skin testing and challenge are negative, the penicillin allergy can be removed from your record. 

An allergy specialist begins the test by taking a history of your allergy. If they suspect you do not have an active penicillin allergy, they may run a penicillin skin test and challenge. This two-part test starts with the provider placing minimal amounts of penicillin onto the surface of the arm. 

An allergy specialist and a team of nurses will then monitor you for a reaction. If you do not react, the provider will proceed with the challenge and administer a dose of penicillin. You will be monitored for an hour after the dose to determine the outcome of the challenge.

If the skin testing and challenge are negative, the penicillin allergy can be removed from your record. If the challenge is positive, then the provider will confirm your penicillin allergy and provide you with information on penicillin-based medications that you must avoid.  

- Allie H.