If you're currently shuddering at the thought that your partner's luscious beard carries more germs than a dog's fur - thanks to a recent proliferation of online headlines claiming just that - you need to keep reading.
Here's the low-down: last year, a team of European researchers really did compare the bacterial load of specimens taken from human beards and a bunch of dogs. But the actual purpose of the study was to investigate whether, from a hygiene perspective, it's okay to use human MRI devices for scanning our four-legged friends.
You see, most vet clinics don't have a dedicated animal scanner, according to the team behind this study, which was published in July 2018 in the journal European Radiology. Those devices are costly to buy and maintain.
But as dogs keep enjoying longer life-spans along with increased diseases in their old age, the need for imaging diagnostics is on the rise.
So, could we just take dogs to human hospitals and scan them there?
"People are afraid that they will contract a zoonosis if they share scanners with their furry friends," the researchers write in their paper, noting that studies have shown we share bacteria with our dog companions anyway, although the actual health risks are less known.
"The main objective of this prospective multi-centre study is to determine whether it would be hygienic to evaluate dogs and humans in the same MRI scanner by comparing the microbial flora of dogs and humans."
To achieve that objective, the team took bacterial samples from the coats and mouths of 30 dogs that had been brought to the hospital for MRI examinations of disorders affecting the brain or spinal cord.
For their comparison group, the researchers picked 18 bearded men who also had upcoming MRI examinations at one of the three radiological departments participating in the study. The team "cautiously" pressed agar plates onto the beards, along with taking swabs from the men's mouths.
(The team doesn't reveal in the paper why they specifically chose bearded men as their comparison group, but we've reached out to the lead author of the study for comment, and will update if we hear back.)
(Gutzeit et al., European Radiology, 2018)
On top of that, the team also sampled MRI scanners to compare whether those used for dogs end up with a higher level of microbes than ones used exclusively for humans.
So, did beards have more microbes than dog coats? Yes, but that doesn't actually mean much as a standalone fact - after all, the vast majority of bacteria are not trying to kill us, and some could actually be beneficial.
Whenever you see an "ahh! germs!" article like that, remember - pop an agar plate on just about anything and you'll likely grow a veritable garden of microbes. Case in point: the mouldy petri dish that scared thousands of social media users last year, for no good reason.
If you're curious, however, here are the results of beard-versus-dog microbial count as outlined in the paper:
"A total of 18/18 men displayed high microbe counts, while seven dogs exhibited moderate microbe counts and 23 dogs had high microbe counts. More human-pathogenic bacteria were found in the men's beard than in the dogs' fur. In 7/18 humans and 4/30 dogs, we found human-pathogenic bacteria. However, this difference does not meet statistical significance (p = 0.074)."
As we already said, the whole point of this exercise was to see whether it's okay to bring dogs into human MRI machines.
In that regard, it's great news for our canine companions.
The team discovered that not only are dogs clean enough to be brought to human hospitals, but MRI scanners actually tend to be disinfected after scanning dogs, leaving the device potentially more hygienic than after a human has been stuck in there.
"In this prospective multi-centre study, we showed that dogs do not pose a significant hygiene risk to humans even if they utilise the same MRI scan facility," the team writes.
But should you be worried about germy beards making you sick? This study was not designed to answer that, although other research has shown that you probably don't need to fret about it.
However, dudes, do wash your beards - if not for the microbial load, then just for the sake of not walking around with a smelly face.
The study was published in European Radiology.