Allergic to Penicillin? Think Again!

Think You’ve Got a Penicillin Allergy? Why You Might Want to Think Again…

When it was discovered in 1928 by Alexander Fleming, penicillin was touted as a miracle drug: An antibiotic that could effectively fight bacterial infections, stopping many previously devastating illnesses in their tracks. While prolonged use has allowed bacteria to develop a resistance to penicillin, it’s still a fundamental part of modern medicine – at least for 90% of the population.

The other 10% have been told at some point in their lives that they are allergic to penicillin. However, a study published by medical experts at Cleveland Clinic shows that up to 90% of that 10% aren’t actually allergic to penicillin. To put it another way, if there were 100 people in the world, 90 of them wouldn’t be allergic at all, while 10 of them would be diagnosed with a penicillin allergy. Of those 10, only 1 of them might actually be allergic, with life-threatening anaphylactic reactions as low as 0.02% to 0.04%. Even then, the Cleveland Clinic research shows that 80% to 100% of patients diagnosed with a penicillin allergy will test negative for it 10 years after their initial reaction.

I’ve been diagnosed with a penicillin allergy. What are the risks if it’s a false diagnosis?

Most people who diagnosed with a penicillin allergy might be fine with just ‘living’ with it. Avoiding penicillin is relatively easy. But the reality is, you are potentially missing out on effective, FDA-approved medications for a huge swath of illnesses and infections. Those with penicillin allergies are told to avoid all drugs in the penicillin family (including the near-universal antibiotic amoxicillin), as well as the closely related cephalosporin family.  According to the CDC, people who are allergic to penicillin can see cross-reactivity rates of 2.5% - 10%. 

The reality is, penicillins are known as some of the safest and cheapest drugs out there, hence their prolonged use by the medical community. People identified as penicillin-intolerant will often be prescribed more powerful and / or broad-spectrum antibiotics, which may kill both good and bad bacteria, cost more, and have more side effects.

How do I find out if I’m actually allergic to penicillin?

Skin testing is a safe and effective tool for identifying whether you still have a penicillin allergy. In fact, according to a Mayo Clinic study, it’s gotten the all clear for children under the age of 18 (even though they are more likely to show a positive reaction). 

You’ll want to schedule an appointment with an allergist, who will conduct a basic and relatively painless skin prick test. If you are still allergic, your skin will likely react by swelling, turning red, or itching. These symptoms should dissipate within an hour, however your allergist / immunologist will be prepared should you have a more serious reaction.

Most allergy tests will last several hours as your allergist may want to monitor your reaction over a period of time, or try different penicillin dilutions. Your allergist will likely also try an oral dose of penicillin or amoxicillin. A skin test alone is not 100% accurate in terms of predicting how your body will respond, and future practitioners will be hesitant to prescribe penicillin to you without this oral test.

If you get the all clear after these two steps, congratulations – you’re likely safe to make the penicillin family part of your medical treatments going ahead!