Doctors sometimes prescribe antibiotics to help treat a cough, but a new study shows the drugs won’t help reduce the severity or duration of coughing — even if a bacterial infection is the culprit.

Lower respiratory tract infections that cause coughing have the potential to become more dangerous, with 3% to 5% of these patients suffering from pneumonia, said lead researcher Dr. Dan Merenstein, a professor of family medicine at Georgetown University School of Medicine, in Washington, D.C.

“But not everyone has easy access at an initial visit to an X-ray, which may be the reason clinicians still give antibiotics without any other evidence of a bacterial infection,” Merenstein said in a Georgetown news release.

This has led some patients to expect antibiotics for a cough, Merenstein said.

To see if antibiotics make any difference, researchers tracked their use in people presenting with lower respiratory tract infections.

About 29% of people were prescribed an antibiotic during their initial medical visit, but the drugs had no effect on their cough compared to those who didn’t get a prescription.

It also took the same amount of time for people to get over their infection, whether or not they got an antibiotic — about 17 days.

The new study was published April 15 in the Journal of General Internal Medicine.

Overuse of antibiotics is increasing the risk that dangerous bacteria will become resistant to the drugs, researchers noted.

“Physicians know, but probably overestimate, the percentage of lower tract infections that are bacterial,” said researcher Dr. Mark Ebell, a professor with the University of Georgia College of Public Health. “They also likely overestimate their ability to distinguish viral from bacterial infections.”

This study highlights the need for more research into coughing, Merenstein said.

“We know that cough can be an indicator of a serious problem. It is the most common illness-related reason for an ambulatory care visit, accounting for nearly 3 million outpatient visits and more than 4 million emergency department visits annually,” Merenstein said.

“Serious cough symptoms and how to treat them properly needs to be studied more, perhaps in a randomized clinical trial as this study was observational and there haven’t been any randomized trials looking at this issue since about 2012,” Merenstein added.