It’s a common enough question in any doctor’s office: "Do you have any drug allergies? Penicillin maybe?" Up to 15 percent of patients in the US will say they’re allergic to penicillin. That's tens of millions of people. But studies have shown that when those patients are challenged with tests, more than 95 percent turn out to be dead wrong.

It might not seem like a big deal, but it is. Penicillin and its close relatives are often first-line drugs. When they’re skipped due to a phantom allergy, doctors land on harder drugs—antibiotics that can be less effective, have more side effects, and spur resistant infections. Indeed, some studies have found that people with penicillin allergies have higher odds of carrying drug-resistant bugs.

Researchers and some physicians have known about this problem for years. But with the intensifying plague of drug-resistant infections and failing antibiotic therapies, more doctors are focusing on it and trying to correct it. In a study set to be published in the Journal of Allergy and Clinical Immunology, researchers found that simple skin tests or guidelines can safely boost penicillin and related prescriptions up to six-fold for patients initially labeled allergic.

“We found that addressing penicillin allergy by either method could lead to an overall improvement in antibiotic choice for these patients,” Kimberly Blumenthal, lead study author and an immunologist and allergist at Massachusetts General Hospital, said in a news release. “We don’t want to discourage any method of evaluation because even thinking about whether a patient’s penicillin allergy is true could lead a provider to make a different management decision.”

Blumenthal and colleagues assessed different methods for beating back allergy myths in internal medicine inpatients at the Brigham and Women’s Hospital over a two-year period. The study was broken into three spaced-out segments. In the first, researchers collected baseline data for penicillin and related prescriptions over five months. In the second, seven-month stretch, they looked at the same data when doctors were prompted to have patients consider taking skin allergy tests before antibiotic prescriptions. And in the last seven-month segment, they looked at prescription data when doctors had a computerized, clinical guideline for making decisions about prescriptions.

Over the whole period, there were 625 patients with a presumed infection and penicillin allergy. That broke down to 148 patients in the baseline, 278 in the second section using skin tests, and 199 in the last using a clinical guideline.

The researchers hit some logistical hurdles in the second segment involving skin tests. They had to rely on moonlighting allergists and nurses to perform the tests, and some patients were ineligible for the tests due to other medications or the possibility of severe reactions. Each patient and the patient’s primary care team also had to sign off on the tests beforehand. Overall, only 43 of the 278 patients ended up getting skin tests.

But of those 43, skin test results showed that none were allergic to penicillin or similar antibiotics. The results prompted a six-fold increased rate of prescribing penicillin and similar drugs in that group.

The clinical guideline group saw a two-fold improvement in prescriptions. That guideline simply prompted doctors to rethink each patients’ allergy and assign him or her into risk categories for having an allergic reaction to a penicillin or similar antibiotic. The risk categories started at “very low risk,” which meant doctors could just give them the antibiotic—allergy shmallergy. Low- and medium-risk groups prompted the doctor to test out a low dose of antibiotic or consult with an allergist. And for the highest-risk patients, the doctor just avoided the drugs.

“The interventions implemented challenged the status quo by introducing a new process (i.e., skin testing) and a new technology (i.e., computerized guideline) to change the care of inpatients labeled ‘penicillin-allergic,'” the authors concluded. Though hospitals and doctors can be slow to change, they’re hopeful that the study offers a few steps forward to improving antibiotic stewardship and patient care.

Journal of Allergy and Clinical Immunology , 2017. DOI: 10.1016/j.jaci.2017.02.005 (About DOIs).