He avoided penicillin for 50 years. He was never allergic.

In the spring of 2024, Steven Dubner developed a cough that would not quit. It turned into a respiratory infection. As Dubner put it, "It hurt to talk or swallow," and laughing set off coughing fits, which kept him from sleeping through the night. He had ferocious night sweats and vivid dreams, and by day his entire body ached, as if he had been hit by a car. With no appetite and no energy, he later called it the worst physical stretch of his life.

For roughly 50 years, Dubner had also believed he was allergic to penicillin. The belief rested on a childhood memory, of what his mother had told him, which was based on what the family doctor had told her. His primary care doctor, Rebecca Kurt, had challenged that history years earlier with a simple question: "How do you know?" She told him that most people carrying that allergy label are not truly allergic, and suggested he get the label removed.

Dubner put it off. Kurt had even given him the phone number for Elena Resnik, an allergist, but he never called. It seemed like a hassle, time consuming and expensive, and he figured it hardly mattered since there were plenty of other antibiotics.

The infection in 2024 changed that calculation. Kurt prescribed azithromycin, sold in a short course often called a Z-pack and commonly used for patients who say they cannot take penicillin. It did not help. He got sicker, and got his lungs scanned to check for cancer. There was no cancer, but he began to wonder whether penicillin could cure him, or whether it might kill him.

He finally saw Resnik. He had a skin prick test and a second test just under the skin, and both were negative. At a later visit, he swallowed a dose of penicillin, and, as Dubner recounted, "I waited in her office for a couple hours to see if I had an allergic response." He did not. He could now say he was not allergic to penicillin, and probably never had been.

By then, his illness had deepened. Further testing found non-group-A strep throat, plus thyroiditis, an inflammation of the thyroid, the butterfly shaped gland in the front of the neck that helps regulate body temperature, heart rate, and other functions. With the penicillin label gone, Kurt allowed him to take amoxicillin, a drug in the penicillin family. The healing was slow, but the cough died down, his voice returned, his energy came back, and he started sleeping through the night again.