Why is penicillin allergy delabeling important?

Penicillin is the most reported drug allergy in the United States, noted in up to seven-10 percent of the population.  However, over 90 percent of patients who are diagnosed with a penicillin allergy can tolerate it and penicillin-induced anaphylaxis is exceedingly rare (0.015%-0.04%).  Having a penicillin allergy label is linked to worse health outcomes including higher antibiotic costs, longer hospital stays, increased risk of drug resistant microorganisms such as C. difficile and methicillin-resistant S. Aureus (MRSA) and increased side effects from secondary antibiotics.  Due to this, current Allergy Society guidelines recommend proactive penicillin allergy delabeling for all patients.

My patient is convinced they are allergic to penicillin. How do I explain they may not be?

I typically explain to people with low-risk history for a true penicillin allergy (those with delayed and non-progressive symptoms such as a maculopapular rash that lasted for three-four days) that the rash was more likely due to the infection itself or a combination of the penicillin and the infection than a true penicillin allergy. These delayed, benign rashes are common (occurring in five-10 percent of patients who receive amoxicillin) and are not a risk factor for a life-threatening reaction in the future.  For those who are not easily convinced, I also share that many people outgrow penicillin allergy. Data demonstrates that 50 percent of people lose sensitization (positive testing) to penicillin after five years and 80 percent of people lose sensitization after 10 years.  Therefore, even if the history is more convincing for a true IgE-mediated penicillin allergy in the distant past, a referral for evaluation is still reasonable.

My patient has multiple family members who are allergic to penicillin, so they avoid it. What should I recommend?

Penicillin allergy is not genetic so there is no need to avoid penicillin due to a family history.  Many patients will be reassured by knowing that their risk of a penicillin allergy is not greater than the general population. For those patients who remain anxious or require additional reassurance, referral to an Allergy & Immunology subspeciality physician is reasonable.  Given the low likelihood of patients in this category having a true allergy, it is not typically recommended to perform skin testing, but these patients may be offered a one-step amoxicillin oral drug challenge to provide additional reassurance.

What should my patient expect when I refer them to an Allergy & Immunology specialist?

The evaluation each patient receives will vary based on their clinical history. Patients with histories which are not consistent with allergies may be delabeled with patient education only.  Patients whose histories are consistent with a true IgE mediated allergy (such as immediate hives or respiratory distress) are typically recommended to undergo skin testing which includes skin prick testing and intradermal testing to the major and minor allergenic determinants of penicillin followed by a drug challenge if the skin testing negative.

Based on a robust amount of evidence showing that majority of patients are not allergic, it is now becoming increasingly standard for patients with a history of a delayed, benign maculopapular rash or urticaria to undergo an oral drug challenge to amoxicillin without starting with skin testing.  This challenge consists of a one-time dose of amoxicillin and monitoring for 60 minutes.  This is currently more actively encouraged in the pediatric population and something to be considered in adult populations based on varying degrees of evidence. 

Is there anything I can do outside of referring them to an allergist?

Yes! In addition to highlighting all the reasons penicillin allergy delabeling is important to your patients, clinicians in all specialties can be essential in not labeling patients with a penicillin allergy in the first place. For example, patients who have a headache or diarrhea only from amoxicillin (or any medication) are better characterized as having a side effect and this is not a contraindication to future use. While there is emerging literature on primary care physicians and/or other subspecialities successfully delabeling patients, at present the majority of active delabeling is done by an allergists.