Allergic to Penicillin? The Answer is Likely “No.”

By Rhiannon Collette

Think you or your child may be allergic to penicillin? You may need to think again.

A new study suggests that millions of Americans falsely believe they have penicillin allergies, and that misunderstanding may be putting them at risk and contributing to the rise of dangerous antibiotic-resistant bacteria.

An estimated 10 percent of people in the United States report being allergic to penicillin, but scientists believe that the number of people with a true allergy is likely much lower, and are now encouraging people who think they have an allergy to consider getting allergy testing to make sure.

Often, people falsely believe they are allergic to penicillin because they experienced a reaction, such as nausea, diarrhea or skin rashes, after completing a course of the commonly prescribed antibiotic. These reactions often are unrelated to the medication, according to the study.

“A common issue is when a child has a viral infection that does not warrant antibiotics, but they receive the medication anyway, and then they develop a viral rash, which is misdiagnosed as a penicillin allergy,” said Dr. Peter Jung, pediatrician and co-founder of Blue Fish Pediatrics in association with Children’s Memorial Hermann.

He and other members of Blue Fish Pediatrics  typically refer children who are suspected of having a penicillin allergy to receive professional care from an allergist who can order testing to confirm whether an allergy is actually present.

Dr. Susan Pacheco, MD, UTHealth pediatric immunologist/allergist affiliated with Children’s Memorial Hermann Hospital said true allergic reactions to penicillin are relatively rare.

“If there is a concern about a true allergy the child should be always referred to an allergy specialist for further evaluation and testing,” Pacheco said. “Based on the history and presentation, combined with testing if indicated, the allergist can determine if this was an allergic reaction.” If indicated, a skin prick test with the antibiotic, and oral challenge test or a combination of both may be performed.

The relatively painless skin prick test is the gold standard for allergy testing and can be done in the allergist’s office. During the test, the skin is pricked or scratched and exposed to a potential allergen, and then observed for signs of a reaction. The tests typically take around 30 minutes and produce immediate results.

Even if you were diagnosed with a penicillin allergy years ago as a child, it’s still important to get tested again, in part because penicillin allergies can wane over time. The study, published in the Journal of the American Medical Association (JAMA), found that 80 percent of patients with penicillin allergies eventually became tolerant of the antibiotic.

It’s important to determine whether you are truly allergic to penicillin, Dr. Jung said. Even though other antibiotics are available to those who cannot take penicillin, these alternatives are often more expensive and may carry more side effects.

Additionally, these “broad-spectrum antibiotics” increase the risk of developing antimicrobial resistance, including methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile (C. diff), which can both cause potentially life-threatening infections and complications.

“Antibiotics are important drugs that are necessary to treat certain infections, but it’s also imperative to use the right ones at the right time,” Dr. Jung said. “That’s why I believe it is so important to be judicious in the utilization of antibiotics.”

Concerned about a possible penicillin allergy? Speak to your doctor about your symptoms and ask about skin prick testing to confirm the presence of an allergy.  To find a doctor for you and your family, call (713) 222-CARE (2273) or click here

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