Authored by Revere Health

The Dangers of a Misdiagnosed Penicillin Allergy

June 13, 2018 | Allergy and ImmunologyValue-Based Care

Penicillin is an antibiotic that doctors use to treat several different types of bacterial infections, and it works by interfering with bacteria cell walls. Its effects were discovered in the early 1900s and has saved millions of lives since.

Approximately one in 10 people in the United States report a penicillin allergy, but research shows fewer than 1 percent of people are truly allergic.

How do people get mislabeled as allergic to penicillin?

A number of reasons can lead to a misdiagnosed penicillin allergy. For example, you may have been given penicillin in the past and shown adverse reactions. Just like any drug, penicillin can produce unpleasant side effects, but these side effects aren’t necessarily allergic reactions and may be mislabeled as such. These adverse reactions may also be your body’s response to the infection your doctor is trying to treat, not the penicillin.

If you had a true penicillin allergy in the past, it’s also possible that you are no longer allergic. Many people outgrow the allergy within 10 years.

The best way to identify whether you are allergic is through testing.

Why should I test for a penicillin allergy if I’ve already been diagnosed?

Misdiagnoses regarding penicillin allergies are incredibly common. More than 90 percent of patients with the diagnosis aren’t really allergic at all. Additionally, a misdiagnosed penicillin allergy may result in the use of less-appropriate antibiotics and compromise the effectiveness of your medical care.

Avoiding penicillins unnecessarily has several disadvantages, including:

Higher medical costs

A 2003 study analyzing antibiotic costs in hospitalized patients found that the cost for penicillin-allergic patients was 63 percent higher than patients without a penicillin allergy label.

Because most patients with a penicillin allergy are not truly allergic, patients may be spending more on their antibiotics than necessary. This results in higher healthcare spending across the country.

Increased antibiotic resistance

Antibiotics are critical in healthcare. They have been able to lengthen life expectancy, successfully prevent and treat numerous infections, and save lives. However, the overuse of antibiotics—patients with a penicillin allergy label tend to use/need more antibiotics—can cause antibiotic resistance. This means that antibiotics are no longer able to control or kill bacterial growth, which can lead to the spread of infection and disease.

Increased length of hospital stays

A study conducted at Kaiser Foundation hospitals examined patients with a penicillin allergy label. They were prescribed broad-spectrum antibiotics (a type of antibiotic that targets a wide variety of bacteria, but may not be as effective for certain infections) instead of penicillin and averaged 0.59 more days in the hospital than patients without a penicillin allergy.

This is dangerous because if you are not truly penicillin allergic, you may be spending more time at the hospital and therefore more money on healthcare costs unnecessarily. The penicillin-allergic patients in this study also had more cases of resistant bacterial infections.

Increased morbidity and mortality

Because patients with a penicillin allergy label are more likely to develop antibiotic resistance, they are also more likely to develop related morbidities (co-occurring problems) such as:

  • Increased length of mechanical ventilation (used to help or replace spontaneous breathing)
  • Increased need of intensive care and invasive devices
  • Excess surgery
  • Functional decline and need for post-acute care
  • Need for contact isolation (a precaution used to prevent the spread of diseases)

If you have been labeled as penicillin allergic, it’s important that you contact an allergist to conduct a simple skin or oral test, as you may have been misdiagnosed or no longer have the allergy. An accurate diagnosis can help you get the most appropriate and cost-effective treatment for your situation.

Our allergy specialists diagnose and treat patients who suffer from allergic and immunologic disorders. We work with both pediatric and adult patients and use the most comprehensive and up-to-date medical therapies.


“Penicillin: How Does Penicillin Work?” MedicalNewsToday.

“Is It Really a Penicillin Allergy?” Centers for Disease Control and Prevention.

“Just the Facts on Penicillin Allergy.” The American College of Allergy, Asthma and Immunology.

“The Economic Burden of Antibiotic Treatment of Penicillin-allergic Patients in Internal Medicine Wards of a General Tertiary Care Hospital.” US National Library of Medicine.

“Penicillin ‘Allergy’ May Be Inaccurate and Costly.” Medscape.

“The Negative Impact of Antibiotic Resistance.” Science Direct.


The Live Better Team


The Live Better Team

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This information is not intended to replace the advice of a medical professional. You should always consult your doctor before making decisions about your health.