The ultimate display of affection — letting your dog slobber your face with its tongue — can actually put your health at risk
Because dog mouths are host to "an enormous oral microbiome of bacteria, viruses and yeast," according to Dr Neilanjan Nandi, an assistant professor of medicine at Drexel University College of Medicine in Philadelphia.
While a dog's saliva has proteins that may help cleanse or heal its own wounds, there are some organisms in the dog mouth that the human body simply cannot tolerate.
In fact, some bacteria in dogs' mouths are zoonotic, meaning a disease that exists in animals can be transmitted to humans
So is there any disease that can be passed from your dog to you?
There are actually a number of illnesses that can be passed from dogs to humans. And gastrointestinal problems is one of the most common of such illnesses.
In fact, it's not just gastrointestinal problems that dogs can spread among their owners.
Dr Joseph Mosquera, chief medical officer and founder of a medical expert-run website, told Medical Daily that, "In my experience, I have seen a lot of skin and respiratory allergies, body funguses like ringworm, and transmission of lyme disease through a tick that jumps from a pet onto a human after being outside."
Medical Daily quoted Dr Mary Beth Leininger, the associate vice president of Veterinary Relations at Hartville Pet Insurance Group, saying that dog mouths should be kept far away from human ones for precisely this reason.
"Because dogs frequently lick around the anus, they can harbour parasite eggs in the saliva," Leininger told Medical Daily, adding, "Should you allow your dog to lick your child's face? The short answer….no."
However, it doesn't mean you shouldn't let your dog lick you at all
"When dog saliva touches intact human skin, especially in a healthy person, it is extremely unlikely to cause any problems, as there will be very little absorption through the skin," Dr. Leni K. Kaplan, a lecturer of community practice service at Cornell University's College of Veterinary Medicine, told the New York Times.
However, he warned that you should avoid letting your dog lick your nose, mouth and eyes, as a dog's saliva and pathogens can be absorbed more easily in these areas.
And while illnesses transmitted this way are rare, it is best to avoid having your dog lick those parts of your face, adviced Dr Kaplan.
Even the former US President, Barack Obama, touched on the subject in an interview with Wired magazine back in August 2016
Obama's concern is also shared by John Oxford, an expert in microbiology and a professor of virology at Queen Mary University of London, who says he would never let a dog lick his face
"It is not just what is carried in saliva," the New York Times quoted him as saying.
"Dogs spend half of their life with their noses in nasty corners or hovering over dog droppings so their muzzles are full of bacteria, viruses and germs of all sorts."
If you're still going to let your dog lick your face, there are some steps/precautions you should practice to ensure your safety
2. Don't let your dog lick you when he/she is sick.
3. Keep your dog away from the faeces of other animals.
4. Remember to wash your face afterwards.