People with a penicillin allergy on their medical record are not given penicillins (or often their relatives the cephalosporins) when they have infections. Instead, the antibiotics prescribed may be broader-spectrum, less effective, and/or more toxic.
Penicillin alternatives may be less effective or more toxic
One recent national study from more than 100 US hospitals with almost 11,000 patients demonstrated that if you have a reported penicillin allergy, you are five times more likely to be prescribed clindamycin than if you do not have that label. Clindamycin is an antibiotic that is highly associated with the potentially life-threatening Clostridioides difficile (C. diff) gastrointestinal infection. A study using comprehensive United Kingdom data recently confirmed that people with a documented penicillin allergy have a 69% increased risk of C. diff.
When patients undergo surgery, a penicillin relative (cefazolin) is often used to prevent an infection at the surgical site. However, according to this study, in patients labeled with a penicillin allergy, cefazolin is routinely avoided in place of a less effective substitute, resulting in a 50% higher risk of surgical site infections for people with a documented penicillin allergy.
Confirming or ruling out a penicillin allergy through penicillin allergy testing could justify the risks of avoiding beta-lactams (the drug class that includes penicillins and cephalosporins), or potentially avert them by allowing doctors to prescribe beta-lactams when they are needed. Even some patients with severe penicillin allergy histories are able to take penicillins safely again, because penicillin allergy often does not persist for life. In all, about 95% of people tested for penicillin allergy in the US are found not to be allergic.
What does penicillin allergy testing entail?
Penicillin allergy testing often begins with an allergy history. In order to know if testing is appropriate, the clinician needs to know some details about the reaction, such as: When did it happen? What were the symptoms? How were you treated?
If appropriate, the next step may be the penicillin skin test. This test involves pricking the skin and introducing a small amount of allergen. Anyone with a positive skin test to penicillin — there’s usually itching, redness, and swelling at the site of the test — is allergic and should avoid penicillin.
People who have no reaction to the skin test can undergo the amoxicillin challenge. In this test, the clinician gives the person amoxicillin (a type of penicillin), and observes for signs and symptoms of an allergic reaction for at least one hour.
Allergists routinely perform penicillin allergy testing. Other types of doctors, nurses, nurse practitioners, and even pharmacists can be trained to perform penicillin allergy skin testing in the US. The amoxicillin challenge test can also be done by a variety of healthcare providers, as long as they are comfortable diagnosing and treating allergic reactions.
New clinical tools may help evaluate likelihood of a true penicillin allergy
There are increasing numbers of clinical tools that can help your primary care doctor,
