Do you have a penicillin allergy in your medical history? You can safely check if it’s still an issue — or if it’s holding you back from effective treatment options.
If you’ve been told you have a penicillin allergy — especially if it was many years ago — it may be time to ask for a second opinion. Penicillin allergies are often misdiagnosed or over-diagnosed, and some kinds of penicillin allergies go away over time. Chances are you may not actually be allergic to this important antibiotic, even if for years you have thought otherwise.
“Between 8% and 15% of all people in the U.S. have a penicillin allergy in their chart,” said Dr. Cosby Stone, an allergist and immunologist with Vanderbilt’s Drug Allergy Clinic. “But what we find is that if you test 100 people, you have to test between 95 and 99 to find even one person who is allergic. So only between 1% and 5% of people who think they are allergic actually are allergic under current practice.”
Could you have been misdiagnosed with a penicillin allergy?
Penicillin allergies are typically diagnosed in childhood, usually before age 3. But often the symptoms that lead to a penicillin allergy diagnosis aren’t actually an allergic reaction, Stone said. “Sometimes the person is being treated for what is thought to be a bacterial infection, but it’s actually a viral infection,” he explained. “Then that viral infection causes a rash, and the drug gets blamed for the rash.”
Viruses, such as mono, can also interact with penicillin in a way that causes a rash. “If you give amoxicillin, thinking that it’s strep throat and not mono, quite frequently the patient will get a rash that’s blamed as being a penicillin allergy, but it’s really a very specific interaction between the drug and the virus,” he said.
Other patients may have experienced minor side effects from penicillin treatment and worried those side effects were indicators of an allergy. “Things like nausea, vomiting and diarrhea can happen with penicillin antibiotics,” he said. “But in isolation, that’s a side effect rather than allergy.”
Can a penicillin allergy go away?
Even if you were diagnosed with this true allergy in childhood, you may have grown out of it in adulthood.
“Unless it was a really severe skin rash that landed somebody in the hospital’s burn unit, or the immune system caused damage to the organs or blood, recent research indicates that people appear to grow out of basically every other form of penicillin allergy,” Stone said.
The benefits of penicillin allergy testing
Removing this specific allergy from your chart when possible removes barriers to care for common illnesses, preventive procedures and life-threatening emergencies.
“It’s never too early to get that penicillin allergy tested, because you can never predict when you are going to need antibiotics. When you show up at the doctor’s office, the emergency room or the operating room, having a penicillin allergy in your chart is going to affect decision-making,” Stone said. “Your care team may have to choose second- and third-line antibiotics that might be less effective. We know from extensive research around the world that this increases your chance of getting an outcome you don’t want, like a prolonged hospitalization, a drug-resistant infection or a failed antibiotic treatment.”
The penicillin allergy testing process
The first thing the allergy team will do is ask you what happened that led to the penicillin allergy diagnosis. “How long ago was that? And what did you have to do for it when you had that reaction?” Stone explained. “Then we can use that history to put people into different categories of risk.”
If your original reaction to penicillin is consistent with something that’s a low to moderate risk, then likely you’ll receive an allergy skin test. If that is negative, you’ll be given a dose of amoxicillin and remain under careful observation for about 90 minutes.
“We’ve removed hundreds of penicillin allergies just by giving somebody a dose of amoxicillin and watching them,” he said. If you tolerate the dose of amoxicillin, that means that you’re not at risk of anaphylactic shock, a severe allergic reaction.
In his time testing for penicillin allergies, Stone said he’s never had a patient experience anaphylaxis during testing.
“We’ve never had to give anyone epinephrine,” Stone added. “We’ve never had to rescue anybody during their penicillin allergy testing. The most useful thing that I say to patients is that the main side effect that essentially everyone experiences is boredom.”
Need testing?
More than 90% of people who are told they’re allergic to penicillin are not. Vanderbilt Asthma, Sinus and Allergy can safely test you for a penicillin allergy. To schedule, call 615-936-2727 or visit VanderbiltAllergy.com.
