Penicillin or Amoxicillin Allergy

Have you ever thought much about your penicillin allergy label? Did you experience hives/rash when young thought to be due to penicillin or amoxicillin and since have been telling doctors that you have a penicillin allergy? If that is the case, then you likely are not actually penicillin allergic. In the United States, Penicillin allergy is confirmed in less than 10% of patients who report penicillin allergy^1,2. 

Of note, there is potential harm of carrying the penicillin allergy label. This includes receiving an overly broad antibiotic treatment that can result in undesired outcomes such as C. difficile infection or antibiotic resistance. Also, the antibiotic regimen chosen in place of penicillin could be less effective.

I personally have de-labeled a number of patients who carried the penicillin allergy label and the process is usually pretty simple. For most patients, the route to de-label penicillin allergy includes coming into the office and taking Amoxicillin under supervision. My standard approach is a 50 mg dose followed by 450mg about 30 minutes later. A monitoring period is done after the final dose.

In cases where severe symptoms were encountered after penicillin antibiotic exposure, allergy testing may be warranted prior to any potential oral challenge. A positive allergy test could preclude trying the challenge.

References:

1. 1. Joint Allergy Task Force on Practice Parameters. Drug allergy: an updated practice parameter. Ann Allergy Asthma Immunol 2010;105:259-73.

2. Staicu ML, Vyles D, Shenoy ES, Stone CA, Banks T, Alvarez KS, Blumenthal KG. Penicillin Allergy Delabeling: A Multidisciplinary Opportunity. J Allergy Clin Immunol Pract. 2020 Oct;8(9):2858-2868.e16. doi: 10.1016/j.jaip.2020.04.059. PMID: 33039010; PMCID: PMC8019188.)