Most People Who Have a Penicillin Allergy...Probably Don't. | I Boost Immunity Skip to main content

Most People Who Have a Penicillin Allergy...Probably Don't.

Do you or someone you know have a penicillin allergy? A whopping one in 10 Canadians reports having had an allergic reaction to penicillin. But did you know that out of all those who report a penicillin allergy, only about 1% of them are truly allergic?

Some people report a penicillin allergy because a relative has an allergy, or because they have experienced an unpleasant reaction after taking penicillin. Diarrhea, abdominal pain, nausea, and rashes are some of the most common reactions.

So when a doctor asks you if you're allergic to penicillin, you're going to think back to that unpleasant experience and report it  - and it's important to do so!

Yet...most people aren't actually allergic to penicillin. There is no genetic link to penicillin allergies - so if a close relative has a true penicillin allergy, it does not mean that you have an allergy too.

Most of the reactions people report, like diarrhea, nausea, and abdominal pain, aren't allergies, but rather a side effect of the antibiotic. Sometimes a rash due to a viral infection can be mistaken for an allergy if a person is also on antibiotics. True penicillin allergy is indeed rare with an estimated frequency of anaphylaxis (i.e. an extreme allergic reaction) at 1 to 5 per 10,000 cases of penicillin treatment.  What’s more, allergies to penicillin tend to disappear 10 years after the last reaction.

If penicillin is the recommended treatment, a second choice treatment may be less effective and could have a higher risk of Clostridium difficile (C. difficile) infection (a severe and sometimes difficult to treat case of diarrhea and inflammation of the large intestine). Using the recommended antibiotic treatment can also help prevent the rise of superbugs (like MRSA and VRE).

And we don't want to contribute to developing new superbugs. Although antibiotics are extremely useful medications for treating bacterial infections, using them unnecessarily (or avoiding the recommended antibiotic for the infection) will make antibiotics less effective as a whole.

Superbugs are a real threat to future generations (and remember, antibiotics don't treat viral infections, so don't take them for colds or the flu).

That’s why it’s so important to rule out – or confirm – an allergic reaction to penicillin. For many bacterial infections, penicillin is our first line of defence.

In short, antibiotics are great, but we need to be vigilant in how we use them. Antibiotics are warranted in some cases, and based on the nature of the infection and your medical history, your health care professional may recommend an antibiotic. Always advise your doctor, dentist or nurse practitioner about any medical conditions or changes to your health, and inform them if you have any allergies to penicillin. They will work with you to determine the best course of action.

MRSA - methicillin-resistant Staphylococcus aureus
VRE - vancomycin-resistant Enterococcus

This article/quiz was developed in partnership with the BC Centre for Disease Control’s Community Antimicrobial Stewardship Team.

Last updated: Nov 5, 2019