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Allergic to penicillin for life? Not so fast

July 03, 2017 | Asal Gharib, MD
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A skin test can confirm whether you're past a penicillin allergy.

Whether you are a senior who has worn a medical ID bracelet all your life or a teen who was diagnosed in early childhood, there's a good chance you have "outgrown" your penicillin allergy.

An 80 percent chance, in fact.

A study conducted by The Cleveland Clinic showed that after a period of 10 years with no exposure, 80 percent of patients who had been diagnosed with a penicillin allergy had lost their sensitivity to the drug.

Why does it matter? The ability to take penicillin may benefit your health as an individual and also benefit the global population. These are compelling reasons to find out if you are truly allergic today.

Why is penicillin often a preferred antibiotic?

For you

  • Penicillin and its close cousins are well-tolerated antibiotics. Stronger, broad-spectrum antibiotics, on the other hand, can have side effects that range from diarrhea and joint pain to more serious and permanent effects. The FDA has recently updated the black box warning on a group of antibiotics known as fluoroquinolones, adding risks of serious nerve damage and tendinitis to previously listed side effects.
  • Penicillin can be better for your body.We have learned how important our gut bacteria is to our digestive health, so it is preferable not to kill off virtually all of our bacterial flora with these powerful, broad-spectrum antibiotics.
  • Penicillin costs less. If we need another good reason to choose penicillin, it is significantly less expensive than nearly all the alternatives.

For all of us

While penicillin as an antibiotic can be highly effective against certain pathogens, it is not as broad or as strong as the alternatives prescribed for penicillin-allergic people. The broader and stronger the drugs we as a populace consume, the more we contribute to the problem of antibiotic resistance and “superbugs.”

This is because hardy bad germs who survive the stronger antibiotic will proliferate or mutate into the next superbug. Taking penicillin instead of a stronger drug is a way we can help stem the growing problem of antibiotic resistance. How you can fight antibiotic resistance ›

Are you still allergic? It's easy to find out

At UCI Health, my colleagues and I often see patients who have listed penicillin among their allergies. Rather than assume the allergy is active, we ask questions, starting with the patient's clinical history.

We ask patients:

  • About the nature of their reaction to help determine if it was a true allergic reaction, and if so, how severe
  • What medications they have taken and tolerated since then
  • How they may have tolerated other antibiotics that are in the same class (beta-lactams)

This history helps us assess the probability that the sensitivity was due to a true allergy, and if it was, whether enough time has elapsed that we can expect a negative test result now.

The allergy testing procedure begins with a skin prick, followed by an intradermal test, which is a small injection just under the skin.

These tests have a high specificity, meaning if they are negative, the chances are good you don't have an active allergy to penicillin. If you have negative results to these tests, we would then give you progressively larger doses over the course of the visit, monitoring you for an allergic reaction. If you have no reaction at that point, there is a high certainty that you can safely take penicillin.

Would I need to be rechecked later?

If you are cleared by these tests, your chances of later becoming resensitized to penicillin and having a clinically significant reaction are very low.

However, allergies are notoriously unpredictable, influenced by many factors, even from one time or season to another. This makes absolute clearance elusive. One thing you can do, if you want to further minimize your risks, is opt for a second-generation derivative of penicillin, like cephalosporin. Fewer people overall have an allergic reaction to this medication.

What if my skin test is positive?

If there is a wheal (a bump on the skin) compared to the negative saline control, we do not continue the test.

If the skin tests are positive, you should use an alternative antibiotic that is equally effective. Or, you can ask to be referred for desensitization, a gradual tolerance-building process increasingly used for both medication and food allergies. 

The gift of 'one less thing'

I began running penicillin sensitivity tests in our UCI Health clinics four years ago, when I was in my immunology fellowship. To this day, I still enjoy hearing the responses of patients who find they can take the medical ID bracelet off and breathe a little easier.

We want to spread the word. There are so many people in the community, including healthcare providers, who don't know about this. We tell them, and they are kind of excited. For people who have lived under the assumption that they would have an acute reaction to penicillin, now they may have one less thing to worry about.

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