Penicillin: am I really allergic?

Did you know that most people who think they are allergic to penicillin, are really not?

In fact, it is estimated that only about 10 to 20% of people who believe they are penicillin-allergic are, in fact, allergic.

As physicians, we so often hear from patients that they have been told they have a penicillin allergy, because their “mom said they had some of a reaction to a penicillin medication when they were young”. The result of this is that the individual has had to avoid penicillin antibiotics all their life.  In some cases, more expensive or even less effective antibiotics have been prescribed for their infections.

Many times reactions to penicillin are labeled as an allergy to the medication when it was really due to some other cause, like the infection itself for which the antibiotic was given, or some other non-penicillin medication being given at the same time. Also, medications can cause adverse side effects due to mechanisms other than allergy. Even if the reaction was truly an allergic one, some people can “outgrow” their penicillin allergy over time. Penicillin allergy is not always a life-long problem.

The good news is that true penicillin allergy can be diagnosed, and identified with a medical evaluation and testing. The test for penicillin allergy involves the following:

  • A small amount of penicillin is injected into the skin of your forearm or back.
  • If you're allergic to the particular substance being tested, you develop a red, raised bump or reaction.

If the skin tests to penicillin are negative, your doctor may choose to give you a “penicillin challenge” in the office, under observation. This helps prove for sure that a person is not at risk for any severe, immediate reaction to the penicillin medication. If the skin test to penicillin is positive, most likely your doctor will recommend that you continue to avoid penicillin and related antibiotics.

So, people do not need to go around not knowing for sure if they are allergic to penicillin because of some vague past medical history that only their parents remember. A simple 1-day visit to any of the AAMGRC allergy providers will go a long ways in helping clarify matters.