Penicillin allergy

author 1, author 2 January 01, 2025 #hypersensitivity #drugs

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Penicillin allergies are frequently reported but overall rare. More commonly is represents a mislabel during childhood from medication intolerances and/or confounding reactions from the infection being treated. While skin testing can be used, the gold-standard diagnostic test is a direct oral challenge.

Our patient's PEN-FAST score is ****
There is no validated clinical tool for risk of allergy in children.
After discussing these risks and others including more rare complications such as we have agreed to pursue a direct amoxicillin challenge with 1 hour of observation

pearls

  • ? not sure if in evidence but some staff tends to wait 6 months prior to challenge since index reaction
  • if reaction was recent, ie. 4-6 weeks ago, the risk of false negative with skin testing is higher.

Toronto approach for adults

  1. if severe reaction history or recent (<1 year) => skin test first. If non concerning history and distant, direct to challenge.
  2. if reaction is delayed, wait for IDT delayed read assuming it is not a high risk reaction (ie SJS TENS)
  3. if negative go forward with challenge. otherwise hold off.