Warning: Those latex gloves your doctor is wearing may be covered in germs.

A new study of hand hygiene in hospitals found that wearing latex gloves makes health care workers less likely to clean their hands before and after treating patients. The finding is concerning, researchers say, because germs can travel through latex gloves, and because they’re often worn when doctors work with bodily fluids and the sickest, most infectious patients. Taking off latex gloves can also cause a “back spray” effect, in which fluids and germs are snapped back onto the wearer’s hands.

As a result, doctors and nurses who don’t wash up after using latex gloves can spread infections through contaminated hands, said Dr. Sheldon Stone, lead author of the study and a senior lecturer in the department of medicine at the Royal Free Campus of University College London Medical School.

“If you’re a patient, you assume that if someone is wearing gloves they’re being careful and protecting you from infection,” he said. “But in fact, their hands could be very dirty.”

The study, published in the December issue of the journal Infection Control and Hospital Epidemiology, is the largest to look at glove use in hospitals and their effect on hand hygiene. The researchers looked at more than 7,000 doctor-patient interactions in 56 wards across 15 hospitals in England and Wales.

The researchers found that the overall hand-washing rate — regardless of whether gloves were worn — was just 47.7 percent, similar to compliance rates for hand hygiene in American hospitals, which average about 40 percent. But when gloves were used, the latest study found, hand washing in the 15 hospitals that were part of the research went down even further, to about 41 percent.

“Gloves are often used when in contact with bodily fluids or the most infective patients, like MRSA patients,” Dr. Stone said. “So in the patient group or the clinical situation where you’re more likely to pick up potentially spreadable germs, health care workers are actually less likely to clean their hands afterward.”

The study found that health care workers wore gloves in roughly a quarter of all contacts with patients, and in 60 percent of those cases did not clean their hands either before or after treating the patient. Many of the interactions that were observed in the study took place in intensive care wards filled with elderly patients.

“These are all heavily dependent patients, and they’ve got the highest risk of having an infection when they’re in the hospital,” Dr. Stone said. “You want to be particularly careful around this population, and yet we’re seeing that hand disinfection before gloving is really very poor.”

It was unclear why doctors, nurses and other hospital workers were less likely to wash or disinfect their hands before and after donning gloves. But Dr. Stone and his colleagues speculated that they might be influenced by a widespread misconception that gloves are impermeable to pathogens. While gloves do lower the rate of hand contamination, germs can still get through. Dr. Stone said he and his colleagues wanted to dispel the myth and get across to hospital workers the idea of “The Dirty Hand in the Latex Glove.”

“We want health care workers to avoid it,” he said. “It’s gross. And it’s not just a British phenomenon. I’m sure if you went all over you would find it.”