allergy to penicillin

What an Allergy to Penicillin Really Means

You’ve been there. You go to a doctor’s office or clinic for the first time and you have to fill out your medical history. There is always that question –“Do you have any drug allergies, and, if so to which drug or drugs.”

Based on your answer, in any subsequent treatment, the medical team will not use that drug in your care. So you think back and you remember a time you had some strange feeling of spaciness after taking an anti-inflammatory, or getting a rash after taking an antibiotic.

So you write down those drugs in the space on your form.

True drug allergy really occurs and it is defined by the medical community as a specific response in a skin test or a specific antibody measured in a blood test. This is known as the IgE response and underlies all true allergic reactions.

In the normal course of things, you don’t need to worry about drug allergies, so you probably didn’t actually get tested for drug allergies when you felt the rash or spaciness. But sometimes our assumptions about drug allergies can be wrong.

For instance, there have been cases of people thinking they had food allergies to turkey that turned out to be due to the antibiotics in the feed of the turkey. In those rare cases, it is extremely useful for people to know the cause of an allergic reaction – to know it’s not the turkey, and that they can safely eat turkey that has not been raised on antibiotics.

This issue came up in a recent paper in the Journal of Allergy and Clinical Immunology: In Practice. The article was “The High Impact of Penicillin Allergy Registration in Hospitalized Patients” by Vad Dijk and others, Volume 4, page 926. They examined about 18,000 hospital patients.

They were asked about drug allergies, including allergy to penicillin. If they said they were, and they came down with an infection, they were treated with antibiotics other than penicillin. Of the patients who ended up needing antibiotics, the ones who reported they were allergic to penicillin had a higher rate of readmission to hospital because of failed control of the infection.

But – of the patients who report allergy to penicillin, only 20% are actually allergic to penicillin. So the mere belief that they were allergic led to a worse outcome for the patients.

UPDATE: In another paper in a more recent issue of the same journal mentioned above, “Allergy profile should be updated after uneventful administration of a penicillin or penicillin-related antibiotic to a patient with penicillin allergy” by Wesley and others, Jan-Feb issue, p. 184), they showed that most patients who had declared penicillin allergy and were nevertheless treated with penicillin (bad medical practice!) suffered no bad reaction.

Moral of the story is, if you think you have allergy to antibiotics, next time you see your doctor have him test you so you really know. Otherwise you may not get the best treatment when you need it.

Julian Gordon
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