Is dog saliva bad for people

Deadly dangers lurk in pet kisses

It was only then that Julie remembered burning the top of her left foot in hot water a few weeks before she became ill. It wasn't a bad burn and she had thought nothing of it when her fox terrier pup licked the wound.

Like Julie, most of us don't know exactly what is in our pets' saliva and how dangerous it is. Normally, our skin and our immune system stand between us and the germs of our pets - but these barriers can be broken.

About ten to 15 percent of all dog bites become infected, with cat bites it is even up to 50 percent. Sometimes the consequences are fatal: According to one study, 26 people who were proven to have died died C. canimorsus had infected. (Would your pets eat you after you died?)

Now scientists have begun describing all of the bacteria that live in the mouths of cats and dogs - and comparing them to our own bacteria. Her work reveals a number of potential pathogens hidden in every sloppy kiss and scratchy lick.

Poses in the mouth of a puppy C. canimorsus pose no great danger. At least a quarter of all dogs and many cats carry the bacterium. It is usually not found in humans. As soon as they got into Julie's bloodstream, her body struggled to fight the infection.

The antibiotics eventually turned things around, but the doctors had to amputate Julie's left leg above the knee, as well as part of her right foot and all of her fingers and toes. "It changed my life in every way," she later told ABC News Australia.

We've rounded up a few of the myths and misconceptions about what's inside the mouths of our furry favorites.


If anyone knows what's floating in the mouth of dogs and cats, it's Floyd Dewhirst, a bacterial geneticist at the Forsyth Institute and a professor of oral medicine at Harvard University. Dewhirst pioneered the study of the oral microbiome - all bacteria living in the mouth - in humans, dogs and cats.

Around 400 to 500 types of bacteria are as common as they are numerous in the human mouth, he says. So far, Dewhirst and colleagues have identified 400 different oral bacteria in dogs and 200 in cats. Dewhirst expects more to be revealed in future studies.

One of the main reasons we get infections from pets, he says, is because our bacterial ecosystems are so diverse.

"If you look at humans and dogs, there is only about 15 percent [of the bacteria] in both species," he says. As a result, many of the bacteria in a dog's mouth are unlikely to be kept in check by our immune system and our own bacteria. The oral microbiomes and dogs and cats overlap by about 50 percent. (Cats domesticated themselves)

“Part of this could be due to the type of food in which the bacteria are evolutionarily specialized,” says Dewhirst. Streptococci, which are good at processing sugar, are predominantly found in the human mouth. "Since cats and dogs don't usually eat donuts, they have almost no strep," he says.

A single lick can transfer countless millions of foreign bacteria, says Dewhirst. Even hours later, they could be detected on human skin. When scientists examined human skin microbiomes, they were surprised to find areas of skin full of canine bacteria in several people.

"If a dog licks you and someone takes a cotton swab five hours later and rubs it over that spot, they could find 50 different types of bacteria in the dog's mouth," he says.


Oddly enough, the story is full of traditions that suggest that dog saliva has more healing powers. Allegedly dogs licked wounds in the ancient Greek temple of the god of healing Asclepius. And there is an old but unconfirmed story of Caesar's armies using dogs to lick the wounds of the injured.

Even if that really happened, that doesn't mean it was a good idea.

Various antibacterial compounds - including small molecules called peptides - are found in the mouths of dogs and cats, but also in human mouths. Even so, the pet tongue is not a magical germ killer.

According to Dewhirst, one shouldn't rely on these compounds to sterilize any wound area. Despite their presence, numerous bacteria live in their environment.

In addition, studies on the antibacterial effects of saliva were taken out of context, says veterinarian Kathryn Primm.

A 1990 study found that dog saliva had a mild antibacterial effect when a bitch licked herself and her puppies, according to Primm. Another study published in The Lancet in 1997 showed that the nitrite in saliva on the skin turns into nitric oxide, which is antimicrobial.

But both studies looked at licking within the same species, not across species. A counterexample is provided by a soldier who had his dog lick his wound in 2016 and spent six weeks in a coma while large parts of his tissue died from a bacterial infection. (What are "Carnivorous Bacteria" and how do you fight them?)


So if a pet's mouth is full of bacteria, how clean does it get after cleaning itself?

The reason domestic cats groom themselves so much is because of their predatory instincts. Wild cats use their rough tongues "to lick the blood out of their fur," says Primm. "They don't want to be found by the smell of their prey."

Dogs, on the other hand, are not that fussy. “If you don't clean a dog yourself, it just stays dirty,” says Primm. "They're not stealthy ninja hunters like cats, so it doesn't matter that much from a survival standpoint."

When cats groom themselves, they also spread bacteria on themselves. However, they evolved along with these microbes and their immune system is tailored to them so that they are not a problem for the cat.