Applicable for the diagnosis of IgE mediated or immediate hypersensitivity reactions.
Gold standard for testing for penicillin allergy is with three tests, PCN administered three different ways: skin prick, an injection, and an oral therapeutic dose.
Increasing amounts of the drug are administered over time and the current negative predictive value is estimated approximately 98%, with a 2-3% false rate of negative reactions after penicillin challenge, and generally mild cutaneous reactions.
Skin testing with penicilloyl polylysine is the most common reagent used to assess penicillin allergy.
Testing progresses from the first to the second and third test, only if the preceding test was negative.
Some patients with a positive skin test have no reaction to an oral challenge, and some with a negative skin test do.
Some specialist believe that an oral challenge is the best way to check whether people labeled penicillin allergic based on the history of low symptoms are really allergic.
Patients labeled as allergic to penicillin in the distant past because of symptoms not likely related to the drug, such as G.I. upset or a headache, can safely undergo go an oral challenge in less than one hour of observation.
Delabeling patients for it to be allergic to penicillin is safe and cost saving.