Guest Blog by Brian Bizik, PA-C

Things that don’t exist in medicine:

  • Accurate chief complaints
  • Patients who give the same history to the nurse and the provider
  • Accidentally dropping the lisinopril (not norco) in the toilet

and…amoxicillin allergy!

Got you with that last one, huh?

Yes, along with Bigfoot and the Yeti, amoxicillin allergy really does not exist. OK, it exists, but for all practical purposes it is not something you are likely to see much. Let me make my case:

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  • Pharmacist Christopher Bland publishes in the Open Forum Infectious Diseases journal that 98% of those with a documented PCN or amoxicillin allergy in their chart did not have a PCN allergy when given an allergy test.
  • In the Journey of Allergy and Clinical Immunology, Labrosse et al. tested 133 children with documented PCN allergy – 3 ended up being positive. Yes, 3.
  • A summary by the American Academy of Asthma, Allergy and Immunology found that 94% or more of those with a clinically documented amoxicillin allergy can tolerate the medication without a problem (reference for this below).

The problem is that since many of the times that we give an antibiotic the infection is viral, the common viral exanthem that follows is labeled as an amoxicillin or penicillin rash. This diagnosis then follows the patient for life.

This is dangerous and costly.

A very nice summary study in the British Medical Journal (Blumental et al. 2018) found that PCN allergy in the chart led to a 69% increase in the risk of getting MRSA and 26% increased risk for C. difficile.

It is important to remember that a true amoxicillin allergy is usually sudden, starting within an hour or so after dosing and presents with hives. Following this phrase there are often longer lasting issues like skin blistering or peeling.

Send patients for testing Multiple studies have shown that testing for amoxicillin allergy is inexpensive (around $300 total in the US) and can save thousands on more expensive (and more broad-spectrum) antibiotics and save on additional treatment for C. diff and MRSA infections.

A tool for you! In JAMA Internal Medicine, 2020;180(5):75-752 Trubiano and his team developed an easy tool to use in your practice. The tool, called PEN-FAST, allows you to ask a few questions and through the answers discover if it’s okay to Rx a PCN or amoxicillin medication. The four features associated with having a more likely allergy were:

  • The reaction was five or fewer years ago (2 points)
  • The patient had angioedema or anaphylaxis with the reaction (2 points)
  • Severe cutaneous skin reaction (2 points)
  • Treatment was needed for the reaction itself (1 point)

If the patient in question has 3 points or less, the likelihood of having an actual reaction to a prescription you might give was around 3%. The authors propose that these four questions can safely allow us to prescribe amoxicillin to those with an allergy listed in their chart. And that doing so saves money and additional problems down the road.

With so many options for dealing with allergies, ThriveAP includes lectures that make it simple. From cardiology and orthopedics to ENT and dermatology, ThriveAP includes a balanced curriculum to help any new grad advanced practice provider catch up to speed. For more information, please reach out to


Brian Bizik, MS, PA-C, is a Physician Assistant with 18 years of clinical experience. He is a frequent speaker for ThriveAP. Currently, Brian is the Respiratory Care Coordinator for the Terry Reilly Health Centers in Boise and Nampa, Idaho.  Brian is also the current Conference Chair and Past President of the Association of Physician Assistants in Allergy, Asthma and Immunology and past member of the Idaho State Asthma Collaborative.  


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