top of page

Penicillin Testing and "Challenge" Details

Penicillin Testing


Penicillin and related antibiotics are some of the oldest and most commonly used antibiotics available. They are active against a wide variety of infections and are generally well tolerated. Unfortunately, penicillin allergy is common. Studies show, however, that when people who report being allergic to penicillin are tested for the allergy, nearly 90% are not allergic, and they are able to take penicillin antibiotics without an allergic reaction. This is because this allergy is often temporary.

Testing for penicillin allergy is available, is a relatively simple procedure, and most often leads to a person who thought they were allergic to penicillin to find out that they are not actually at risk.


Components of the Penicillin Allergy Test
Penicillin allergy testing involves the use of various skin testing techniques, including prick skin testing and intradermal skin testing, with different penicillin products.


How Testing Is Performed
Generally, prick skin testing is performed first, which is able to identify the most sensitive penicillin-allergic people. If prick skin testing is positive, then the person is considered to be allergic to penicillin, and no additional testing is done. If prick testing is negative, then intradermal skin testing (very small needles inserted under the top skin layer) is performed with the same materials. Intradermal skin testing identifies more people with penicillin allergy, but it is potentially dangerous in the most sensitive people. This is the reason why prick skin testing is performed first.

If skin testing to penicillin is negative using both prick and intradermal techniques, then the chance of the person being allergic to penicillin is less than 5-10%. The next step will be to give an oral dose of a penicillin antibiotic (ex. amoxicillin) in our supervised medical setting and monitor the patient for at least 75 minutes. This is to ensure that the person can tolerate the antibiotic while we have emergency medicines available.

If any of the above-mentioned tests are positive, then a person is considered allergic to penicillin. In this situation, penicillin and related antibiotics should be avoided. If a doctor determines that there is a special need for penicillin, and the use of other antibiotics will not be sufficient, then penicillin desensitization can be considered. This is complicated and has serious risks, so it is best only to consider this when necessary and in consultation with the allergist.



Will the challenge be done if the patient is sick?

If the patient has a cold, flu, cough, wheeze, hives, worsened eczema, other rash, throat symptoms, vomiting or fever, the test will most likely not be done. Please contact the office to discuss symptoms and reschedule the challenge if needed.

Challenge guidelines and what to expect

  • Please hold all antihistamines for five (5) days prior to the appointment. There is no need to stop asthma medications or nasal steroids. Please call the office if you are unsure what medications to stop.

  • No food should be eaten by the patient two (2) hours before arriving for challenge. Clear liquids or lollipops are okay to allow in those two hours.

  • A challenge appointment can last up to 3 hours, so please plan your day accordingly and bring something to keep you busy.

  • You are responsible for bringing the medication which will be tested to the appointment. This will be sent to your preferred pharmacy when the appointment is confirmed.

bottom of page