Antibiotic Allergy Testing

Also known as: drug allergy testing, antibiotic allergy testing.

What is penicillin allergy testing?

Penicillin allergy testing is a method for allergists to determine if a patient has a penicillin allergy. This is the only standardized drug allergy test available. There are no other antibiotic allergy tests. It is important to test for penicillin allergy because approximately 10% of the population reports they have a penicillin allergy, but of those patients, more than 90% do not actually have a penicillin allergy. Part of this is because it is likely a person will lose their penicillin allergy over time. Even if a patient had a severe allergic reaction (anaphylaxis), 5 years out from the initial reaction approximately 50% have lost their penicillin allergy, and 10 years out from the initial allergic reaction, about 80% have lost their penicillin allergy.

What happens during the procedure?

Penicillin testing has a very good negative predictive value, which means that if the test is negative, it is likely that the patient does not have a penicillin allergy. Often if the test is negative, a challenge with a penicillin medication is done in office, as this would confirm that there is no penicillin allergy. The test involves several skin pricks, which are plastic devices that introduce the allergen into the skin. If this is negative, intradermal injections are done, which involves a small needle that injects the allergen under the skin. If this is negative, then a challenge to penicillin is usually done. Blood tests for penicillin allergy are not accurate and should not be used to determine if a patient has lost their penicillin allergy.


Is any special preparation needed?

You will need to stop all antihistamines for 5-7 days prior to the visit.

What are the risk factors?

There is a small chance of allergic reaction with the testing and with the challenge. These symptoms can include hives, swelling, difficulty breathing, nausea, vomiting, stomach cramping and/or diarrhea. The patient will be monitored closely for any of these symptoms, and given medication promptly to reverse these symptoms if they occur.

Reviewed by: Amy S Feldman, MD

This page was last updated on: January 17, 2022 11:45 AM