Do 90% of people outgrow a penicillin (antibiotic) allergy or never develop one?

From the Guidelines

Yes, it is true that approximately 90% of people who report having a penicillin allergy either never had a true allergy or have outgrown it. This is supported by a recent study published in the Journal of Allergy and Clinical Immunology in 2022 1, which found that when evaluated for penicillin allergy, 90% of individuals who reported a history of reacting to a penicillin class antibiotic tolerated penicillins and were therefore labeled allergic unnecessarily.

Key Points

• The penicillin allergy mislabel is not benign and can lead to the use of less effective, more toxic, or more expensive antibiotics, compromising optimal medical care and increasing costs 1.
• Patients with a history of penicillin allergy are more likely to develop vancomycin-resistant Enterococcus, Clostridium difficile, or methicillin-resistant Staphylococcus aureus, and have longer hospital days and higher medical costs, compared with nonallergic controls 1.
• Removing the penicillin allergy label, such as via negative penicillin skin testing and challenge, leads to improved antibiotic selection with decreased use of broad-spectrum antibiotics 1.

Recommendations

• Patients who believe they have a penicillin allergy should consider discussing allergy testing with their healthcare provider, as testing can help determine whether the allergy is real or not 1.
• A proactive effort should be made to delabel penicillin allergy whenever possible, and strong efforts should be made to educate patients and clinicians about the benefits of delabeling 1.

From the Research

Penicillin Allergy Prevalence

• Approximately 10% of the US population reports an allergy to penicillin, but clinically significant IgE-mediated or T lymphocyte-mediated penicillin hypersensitivity is uncommon (<5%) 2.
• The rate of IgE-mediated penicillin allergies is decreasing, potentially due to decreased use of parenteral penicillins, and because severe anaphylactic reactions to oral amoxicillin are rare 2.
• IgE-mediated penicillin allergy wanes over time, with 80% of patients becoming tolerant after a decade 2.

Evaluation and Management of Penicillin Allergy

• Direct amoxicillin challenge is appropriate for patients with low-risk allergy histories 2.
• Moderate-risk patients can be evaluated with penicillin skin testing, which carries a negative predictive value that exceeds 95% and approaches 100% when combined with amoxicillin challenge 2.
• Many patients report they are allergic to penicillin, but few have clinically significant reactions, and evaluation of penicillin allergy before deciding not to use penicillin or other β-lactam antibiotics is an important tool for antimicrobial stewardship 2.

Outgrowing Penicillin Allergy

• Studies indicate that ∼98% of patients who report penicillin allergy are not acutely hypersensitive 3.
• A significant percentage of patients who were once allergic to penicillin may no longer be allergic, with one study suggesting that 80% of patients become tolerant after a decade 2.
• The exact percentage of people who have outgrown penicillin allergy or never had one is not explicitly stated in the provided studies, but it is clear that a large proportion of reported penicillin allergies are not clinically significant 3, 2.