A small European study has found that the average man's beard is more replete with human-pathogenic bacteria than the dirtiest part of a dog's fur.
For the study, published in the February 2019 issue of the journal European Radiology, researchers analyzed skin and saliva samples from 18 bearded men (whose ages ranged from 18 to 76), and fur and saliva samples from 30 dogs (whose breeds ranged from schnauzer to German shepherd), at several European hospitals.
The researchers were looking for colonies of human-pathogenic bacteria in both man and dog — not in an attempt to beard-shame the hirsute masses, but rather to test whether it was safe for humans to use the same MRI scanners that dogs had previously used. [6 Superbugs to Watch Out For]
In fact, it was the humans who were the dirtier patients. Not only did the men's beards contain significantly more potentially-infectious microbes than the dogs' fur, but the men also left the scanners more contaminated than the animals.
"As the MRI scanner used for both dogs and humans was routinely cleaned after animal scanning, there was substantially lower bacterial load compared with scanners used exclusively for humans," the researchers wrote in the study.
To scan a dog
In their new paper, the researchers analyzed dogs that were scheduled for "routine" MRI scanner appointments to look for brain and spine disorders, the authors wrote. Because MRI scanners are too expensive for most veterinary clinics to own and operate, these tests were conducted at the radiology department of a European hospital that performs about 8,000 MRI scans of human patients every year.
The researchers swabbed each dog's mouth for bacteria samples, then took a simple fur sample by rubbing a special bacteria-collecting plate between each dog's shoulder blades (a "particularly unhygienic" spot where skin infections are regularly encountered, the researchers wrote). After the pooches completed their MRI scans, the researchers took samples from three spots in the scanner, too.
Meanwhile, the team also collected bacterial samples from the beards of hospital patients who were due for MRI scans of their own. The beardos were in relatively good health, and had not been hospitalized any time in the previous year.
My beard contains multitudes
The tests showed that all 18 men showed "high microbial counts" on their skin and in their saliva, whereas only 23 of the 30 dogs did, the researchers wrote.
Seven of the men and four of the dogs tested positive for human-pathogenic microbes — the kind of bacteria that can make a person ill if they colonize the wrong part of the host's body. These microbes included Enterococcus faecalis, a common gut bacteria that is known to cause infections (especially urinary tract infections) in humans, and several cases of Staphylococcus aureus, a common skin/mucous-colonizing bacteria that may live on up to 50% of all human adults, but can cause serious infections if it enters the blood stream.
Despite the comparatively higher microbial counts in this small sample of bearded men, the takeaway from this study isn't, "reach for that electric razor NOW, Rasputin!"; as the authors wrote, "there is no reason to believe that women may harbor less bacteriological load than bearded men."
Instead, it's that humans leave way more potentially-infectious bacteria behind in hospitals than you'd like to imagine — and simply sanitizing a surface is apparently not enough to solve the problem.
"The estimated number of healthcare associated infections (HAIs) in US hospitals was calculated to be approximately 1.7 million patients per year," the authors wrote. Around 100,000 people died as a result of those infections every year, the authors wrote.
"The central question should perhaps not be whether we should allow dogs to undergo imaging in our hospitals," the team concluded, "but rather we should focus on the knowledge and perception of hygiene and understand what poses real danger and risk to our patients."
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Originally published on Live Science.
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Brandon is the space/physics editor at Live Science. His writing has appeared in The Washington Post, Reader's Digest, CBS.com, the Richard Dawkins Foundation website and other outlets. He holds a bachelor's degree in creative writing from the University of Arizona, with minors in journalism and media arts. He enjoys writing most about space, geoscience and the mysteries of the universe.