This article was originally posted in the Montreal Gazette.
Penicillin allergies are common. Supposedly. If you took a random selection of patients, perhaps 10 per cent would say they were allergic to penicillin. But most of them aren’t. In fact, if you take people with a self-reported penicillin allergy and subject them to testing, over 90 per cent will not have a documented allergy. There are in fact a lot of people walking around out there who think they are allergic to penicillin when they aren’t. It’s bad for the system, bad for the patients, and we need to get better at de-labelling false penicillin allergies.
The issue with a penicillin allergy is that it disqualifies you from taking a wide array of medications. Amoxicillin is off the table but in many patients so are antibiotics like cephalosporins, which are similar enough to penicillin that cross reactivity is possible. The likelihood of cross reactivity is fairly low, less than 10 per cent, but the fear of provoking an allergic reaction often forces physicians to prescribe other antibiotics. Though this may seem reasonable and harmless, bypassing common antibiotics for other drugs like vancomycin not only raises costs but also contributes to antibiotic resistant organisms like VRE.
De-labelling — removing a listing of a penicillin allergy from a patient’s file — is the obvious answer. Often a detailed history will reveal that the allergy is not really an allergy. For example, if a patient was prescribed antibiotics and then developed nausea or diarrhea, that is not an allergy — it’s a side-effect.
All drugs have side-effects. But an allergy is when your body produces a specific IgE antibody in response to the presence of the medication. Some allergic reactions can be minor, but severe reactions can result in anaphylaxis. Throat swelling that blocks the airway or a sudden drop in blood pressure can be life threatening unless someone can administer epinephrine quickly. Some patients may not know the details of their supposed allergic reaction. If it happened when they were children, they may be relying on poorly remembered comments made by their parents. But in many cases, a detailed history can go a long way in clarifying and identifying patients who probably don’t have a true allergy.
In many cases, a confirmatory test will be necessary. Skin testing can be done by an allergist to confirm or exclude the possibility of a penicillin allergy. But a recent study in the Canadian Medical Association Journal showed that in low-risk patients, penicillin allergies can be de-labelled even in primary care settings. The study was conducted in a sexually transmitted infection clinic where, for obvious reasons, antibiotic prescriptions are common and penicillin allergies complicate the treatment plan. They identified low-risk patients and performed an oral penicillin challenge. Essentially, an oral challenge involves giving patients an antibiotic like penicillin to determine if an allergic reaction occurs. If there is no reaction, there is no allergy. If an allergic reaction does happen, the medical personnel are there to administer epinephrine and other emergency aid if necessary.
The study was able to de-label the penicillin allergy in the 28 patients who enrolled, though two patients were considered high risk and had to be referred to an allergist for testing. Still, the study demonstrates the feasibility of an approach to remove the allergy label in low-risk patients. In an STI clinic like this one, the benefits of being able to use common antibiotics rather than second-line agents are clear. The practice also need not be limited to antibiotics. While penicillin allergies are the most commonly reported drug allergies, being able to eliminate other possible but unproven allergies, like to Aspirin, would be very helpful in many circumstances.
Too often, poorly described diagnoses carry forward in patient charts and rarely get reassessed. Allergies are one such example. Time, accessibility and practicality are often limiting factors. But removing these labels is important and well worth the extra time and resources it takes to get it right.
