Is your Penicillin allergy real?

General
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We hear it all the time: ‘I’m allergic to penicillin.’ Most patients repeat it without a second thought, usually because someone once told them so. But the truth is, penicillin allergy is one of the most over-reported drug allergies. Infections themselves can cause rashes or reactions, and these often get mistaken for drug allergies. The result? Patients miss out on first-line, effective antibiotics and end up on broad-spectrum ones instead.

While 10% of the people report a penicillin allergy, fewer than 1% are truly allergic (CDC factsheet). This post is about what we as healthcare professionals can do when a patient presents with a self-reported penicillin allergy.

Summary of risks of penicillin allergy label
Summary of risks of penicillin allergy label1950×917 168 KB

Try to evaluate allergy through….

  • Patient history
  1. Setting- Home, EMD/office, or hospitalization
  2. Symptoms- Clinical features, labs, pathology, pictures
  3. Date of reaction
  4. Concurrent medications (e.g., NSAIDs) or coincident infections
  5. Subsequent exposures and outcomes, if any
  6. Drug details- name, route, dose, timing (immediate < 6h or delayed)
  7. Management- epinephrine, steroids, antihistamines
  8. Time to resolution
  • Further work-up (If history suggests a possible IgE-mediated reaction)
  1. Skin testing- Detects allergen-specific IgE using standardized reagents
  2. Drug challenge- Supervised administration (often amoxicillin) in low-risk patients

When can you delabel?

  • Based on low-risk history: if patients’ history shows other symptoms (GI upset, headache, vague childhood rash), reaction was mild and > 10 years ago, or non-IgE-mediated symptoms such as delayed mild rash without systemic features.
  • Moderate or high-risk history (IgE-mediated or unclear): delabel patients only with negative skin test results who tolerate the drug challenge.
  • Delabel patients who tolerate one full dose of penicillin antibiotic.

Severe cutaneous/systemic reaction history: never re-challenge. Keep label.
Note: In cases where tolerability was induced temporarily, allergy label still remains.

Here’s the link for a detailed read: Evaluation and Management of Penicillin Allergy- JAMA Review

Share your experience if you have come across such patients in your practice.
Happy delabeling!

MBH/AB

Penicillin: Add your Pointers to this Antibiotic!