Surgeons for years have stepped into operating rooms wearing their surgical cap — a snug covering that ties in back and comes in standard-issue blue or hundreds of personalized designs.
But a crackdown appears to be underway on that almost sacred piece of headgear.
Inspectors in January reprimanded operating room staff at Brigham and Women's Hospital in Boston for having the hair around their ears uncovered during surgery — and for sporting visible facial hair. And a New York surgeon was written up for showing 3 inches of hair at the nape of his neck.
For sure, other operating room staff wear surgical caps, but they have long been the hat of choice for many surgeons. The problem is the hats usually leave small amounts of hair and the ears exposed — a situation that an influential nursing group says could promote infection.
Regulators have taken the nurses' concerns to heart, forcing some hospitals to switch to shower cap-like "bouffants,'' which can be pulled down over a wearer's entire head.
Now, the American College of Surgeons is fighting back with its own guidelines, arguing there is no reason to tamper with tradition.
Dr. David Hoyt, the organization's executive director, said surgeons are unhappy because they are "being required to use a type of headgear that they've never used in their career.'' Some feel bouffants are hot and uncomfortable.
"I hated it and never wore it,'' said Dr. Michael Zinner, the Brigham's former surgery chief and now founding chief executive of the Miami Cancer Institute. "It irritated my ears and it was sloppy on the top of my head.''
The citations for uncovered hair are based in large part on standards developed by the Association of periOperative Registered Nurses, which says hair, like skin, harbors bacteria that can disperse into the environment and fall on patients.
But last month, the 80,000-member American College of Surgeons published its first dress code. It takes issue with the nurses on hats and on several other fronts.
The surgeons say their recommendations are based on "professionalism, common-sense, decorum, and the available evidence.'' The statement points out that the skull cap "is symbolic of the surgical profession'' and argues there is no evidence linking modest amounts of uncovered hair to wound infections.
Since the surgeons' group released its guidelines, the nurses fired back with a point-by-point rebuttal published in its newsletter and on its website and Facebook page.
"Wearing a particular head covering based on its symbolism is not evidence-based, and should not be a basis for a nationwide practice recommendation,'' the nurses' group responded.
"Our emphasis is on patient safety,'' said Ramona Conner, a nurse who is editor in chief of the association's Guidelines for Perioperative Practice.
Who will have the last word? The Joint Commission, a major hospital accrediting agency, and the US Centers for Medicare & Medicaid Services, which also has rebuked hospitals for improper operating room attire, including Lenox Hill Hospital in Manhattan last October.
A federal official said the Medicare agency accepts the guidelines of the nursing organization, which are similar to those from the World Health Organization and the US Centers for Disease Control and Prevention. But the Joint Commission told the Globe it is currently "conducting an analysis of the major guidelines.''
"Once this is competed, we will be able to provide our position,'' said spokeswoman Elizabeth Eaken Zhani.
Over the past few years, hospital inspectors have cited operating room staff on a variety of attire infractions, including wearing warm-up jackets and earrings in surgery — and for walking into restrooms and cafeterias with surgical booties and dangling masks. All are considered unsanitary.
The guidelines from the American College of Surgeons, with headquarters in Chicago, address a range of issues, recommending, for example, that surgeons change soiled scrubs before meeting with a patient's family. They say scrubs should be covered with a clean lab coat if worn outside the operating room but should never be worn off hospital property. While the nurses agree with the final point, they say there is no evidence that lab coats protect scrubs from contamination.
But the real flashpoint seems to be hats.
The Denver-based nurses organization, a nonprofit that represents 160,000 operating room nurses, said several studies show that hair harbors bacteria. And a study in the 1970s linked two outbreaks of post-surgical wound infections to germs on staff members' hair and scalp.
But whether the type of hat — or any hat at all, for that matter — affects infection rates is unclear. It's hard to conduct randomized clinical trials, the gold standard in research, because that would potentially expose patients to the risk of infection from health care workers whose skin and hair were uncovered, the nurses said.
Two large reviews of published studies in the last five years found little or no evidence that head covers prevent surgical infections.
"There are lots of different practices and very little data,'' said Dr. Gerard Doherty, chief of surgery at Boston Medical Center. "Making a lot of rules around meaningless stuff distracts from the real issue. Most bacteria that causes infection is from the patient themselves.''
After word spread that the Joint Commission had found fault with the Brigham, Doherty said the Boston Medical Center operating room executive committee did its own review of the research and could not find anything to support the strict use of bouffants.
Doherty said his preference is still the paper surgical cap, which covers his short hair in back.
Click through the Brigham website, particularly photos from its well-known face and arm transplant operations, and surgeon after surgeon is seen wearing surgical caps, some brightly adorned with sports team logos. Now, bouffants are officially required, and the hospital provides special beard coverings, which are larger than typical masks.
After it became aware of the increased scrutiny, Beth Israel Deaconess Medical Center in Boston took away surgeons' traditional scrub hats. Dr. Daniel Jones now wears a bouffant pulled down over his ears — but he's not thrilled about it. "Doubt the ear hairs pose any threat,'' he said in an e-mail. "Some actually wear a scrub hat under the bouffant to dress it up.''
Zinner said that several years ago a patient who made significant donations to the Brigham developed a bad surgical infection. The patient's primary care doctor suggested it was because the surgeon was bearded. The donor approached Zinner, and the surgery chief commenced a study to quantify the amount of bacteria on the faces of about 200 clean-shaven health care workers compared with about 200 with beards.
"There was no difference,'' Zinner said.