Author: Nkiruka Erekosima, MD, MPH

Why should you care about Penicillin Allergy testing?

As an Allergist-Immunologist, the most common drug allergy that I encounter is penicillin allergy, but there is not enough education/communication to the general population regarding the importance of getting penicillin allergy evaluations.

Approximately 10% of people in the U.S. report a history of penicillin allergy. To me, the keyword here is “history.”  This indicates that at some point, the person either had an adverse reaction to penicillin or was told that he/she is allergic to penicillin. The person may or may not recall when the reaction occurred or the symptoms of the reaction. In my experience, many individuals who report a history of penicillin allergy express that the reaction occurred several years ago and they do not recall the reaction or that they were told by a parent that they had a reaction to penicillin during childhood. In fewer situations, the individual recalls the details of the reaction to penicillin.

It is important to note the following facts about penicillin allergy:

While up to 10% of people in the U.S. report a history of penicillin allergy, studies have shown that more than 90% of those who report a history of penicillin allergy, are not actually allergic to penicillin. This means that 9 out of 10 people who report a history of penicillin allergy are avoiding penicillin for no reason.

Not all symptoms that occur while taking penicillin are true allergic reactions. Infections may contribute to symptoms that are confused with allergy (such as skin rashes).

Even in people with a true allergy to penicillin, over 80% will lose the allergy over a 10 year period after their initial allergic reaction. This means that Penicillin allergy does NOT last forever!

Key fact: When evaluated and tested by an Allergist-Immunologist, over 90% of individuals who were labeled as having penicillin allergy actually have negative allergy test results and can tolerate penicillin.

If there are other alternatives to penicillin, why should you even bother seeing an Allergist for penicillin allergy testing?

I often hear people say “I have other [antibiotic] options, so I don’t think I need to do the penicillin allergy evaluation.”

If you have a history of penicillin allergy and you have not had allergy testing for penicillin allergy, there are some important reasons why you should see an Allergist for a penicillin allergy evaluation.

Penicillins are the safest and most effective antibiotics for treating many infections.

Penicillin allergy testing

Many of the alternative antibiotics used to treat people labeled as “penicillin-allergic” are broad-spectrum antibiotics.

Broad-spectrum antibiotics are active against a wider number of bacterial types and should be used only when necessary. Oftentimes, a broad-spectrum antibiotic is not the most effective antibiotic for a specific infection and when used, it can lead to suboptimal therapy and potentially prolong the illness or symptoms, which can have a negative impact on a person’s quality of life.

From the standpoint of the larger healthcare system, the use of broad-spectrum antibiotics in patients reporting a history of penicillin allergy is associated with higher healthcare costs, increased risk for antibiotic resistance, and suboptimal antibiotic therapy. Correctly identifying those who are not truly allergic to penicillin can help reduce the unnecessary use of broad-spectrum antibiotics.

Therefore anyone who has been told they are allergic to penicillin, but who has not been tested by an allergist, should get tested.

When should you get penicillin allergy testing and how is this testing done?

It is important to know whether or not you are still allergic to penicillin before you get into a situation where you need an antibiotic. The reason is that if you need an antibiotic to treat an infection, you want to ensure that the infection is treated promptly with the most effective antibiotic. This way you avoid getting into a situation where an alternative antibiotic may not be effective as this can potentially prolong the infection or symptoms. Do NOT wait until you need penicillin to get evaluated.

An allergist will work with you to determine if you are truly allergic to penicillin. The evaluation involves obtaining your medical history regarding penicillin allergy, performing a physical examination, and subsequently penicillin skin testing. If penicillin skin testing is negative, oral penicillin or amoxicillin is often administered, followed by an observation period — this is called a drug challenge.

If there is no reaction during the drug challenge, it means that you are not at risk of having a serious immediate reaction to penicillin, and penicillins can be used in your care thereafter. It typically takes about 2 to 3 hours to complete all of the testings.

Depending on a patient’s history, some patients may proceed directly to a drug challenge without prior penicillin skin testing.

Immediate allergic reactions to penicillins typically occur less than 1 hour after receiving a dose of the medication. Symptoms frequently involve the skin and include hives, swelling of soft tissues of the face, hands, and feet; these are usually treated with antihistamines and steroids.

Rarely, more severe symptoms that indicate anaphylaxis may occur. These include swelling of the tongue/throat/lips, difficulty breathing, coughing, chest tightness, wheezing, abdominal pain, nausea, vomiting, diarrhea, low blood pressure, abnormal heart rate, feeling faint, lightheadedness, loss of consciousness. Severe symptoms require immediate treatment with epinephrine.

If your allergy evaluation reveals that you are truly allergic to penicillin, the allergist will help determine what your options are for treatment. If you are not allergic to penicillin, you will be able to use penicillins that are often safer, more effective, and less expensive.


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