Think you have a penicillin allergy? The good news is you may not!

Penicillin Allergies

Roughly 10% of the population believes they have a penicillin allergy. The truth is that fewer than 10% of people with a reported penicillin allergy actually have one. This topic has garnered significant attention recently after a large review article published by the Journal of the American Medical Association highlighted this important issue. The article – jointly endorsed by the American Academy of Allergy, Asthma and Immunology, the Infectious Diseases Society of America, and the Society for Healthcare Epidemiology of America – urges individuals who have been diagnosed to confirm with a certified allergist for a variety of reasons.

Even if someone had a true allergic reaction to penicillin, this particular allergy often dissipates after about ten years. Once someone has confirmed with an allergist that they are no longer allergic, the patient often times has better future treatment of infections, fewer dangerous side effects of the antibiotics used in place of penicillin, and overall lower cost of care. Penicillins tend to be safer to use than the antibiotics which are used instead in those who are labeled as allergic.

Patients can get mislabeled as allergic to penicillin in a number of ways. They may have experienced drug-related side effects like, headaches, nausea or diarrhea, which are not true allergic reactions. Alternatively, they may develop a rash. While rashes can be a sign of an allergic reaction, many rashes that occur with amoxicillin or penicillin are actually caused an underlying viral illness. One visit to a board-certified allergist can help determine of the allergy is still present.

Our 3 board-certified allergists are happy to help confirm if you have a penicillin allergy. You can schedule an appointment by calling us at (651) 641-6134.

So, what do you need to know about Penicillin?

1. What is penicillin?

The penicillin family of antibiotics contains over 15 chemically related drugs (e.g. penicillin, ampicillin, amoxicillin, amoxicillin-clavulanate, methicillin) that are given by mouth or injection for the treatment of many bacterial infections. It is one of the most frequently used classes of antibiotics in the world.

2. How common in penicillin allergy?

Approximately 10% of patients report an allergy to penicillin. However, most patients (greater than 90%) may not truly be allergic. Most people lose their penicillin allergy over time, even patients with a history of severe reaction such as anaphylaxis.

3. How do I know if I am still allergic to penicillin?

A highly sensitive penicillin skin test is available to diagnose penicillin allergy and can be used to determine if you are allergic to penicillin. An allergist / immunologist can perform this testing, and if it is negative, there is a very high chance that the allergy is no longer present.

4. Is penicillin allergy genetic?

There is no predictable pattern to inheritance of penicillin allergy. You do not need to avoid penicillin if a family member is allergic to penicillin or drugs in the penicillin family.

5. Do I need to see an allergist / immunologist if I already know that I am allergic to penicillin?

Even if you think you are allergic to penicillin, allergies change over time and it is worth discussing your history with your allergist / immunologist who may suggest testing to help clarify your allergy history.

6. I was told that I was allergic to amoxicillin, do I still need to see an allergist / immunologist?

Amoxicillin is in the same family of antibiotics as penicillin. Your allergist / immunologist can review your history and perform skin testing to help you understand if you are still allergic to amoxicillin. This skin testing is similar to penicillin skin testing.

7. Is skin testing painful and what are the risks?

A skin prick test, also called a scratch test, checks for immediate allergy and is the first step in skin testing. Skin prick testing is usually not painful. You won’t bleed or feel more than mild, momentary discomfort. Intradermal skin testing is the second part of the evaluation and involves injecting the skin. The test, if positive, will cause local itching and redness with swelling at the site where the test is performed. Systemic reactions such as hives can occur but are very rare and allergist / immunologists are prepared to treat such reactions.

8. Do I need to avoid other drugs if I am allergic to penicillin?

This largely depends on your history and an allergist / immunologist can help clear this up. It is generally recommended that you avoid all drugs in the immediate penicillin family (amoxicillin, ampicillin, amoxicillin-clavulanate, dicloxacillin, nafcillin, piperacillin-tazobactam as well as certain drugs in the cephalosporin class (a closely related class to penicillins). Although the cephalosporins are close relatives of penicillins and share a structure called the beta-lactam ring, the risk of a cross-reactivity reaction between penicillins and cephalosporins remains <5%. Therefore, even with a true allergy to penicillin, there is an excellent chance you could tolerate cephalosporins.

Modified from a recent Q&A published by the American Academy of Allergy Asthma and Immunology: https://www.aaaai.org/conditions-and-treatments/library/allergy-library/penicillin-allergy-faq