You’ve probably heard it said that a dog’s mouth is cleaner than a human’s because it contains stuff that kills germs.
You’ve probably heard that it’s good for a dog to lick a human wound to kill germs and prevent infection.
Canine saliva does contain antibacterial chemicals, and it can kill some germs on superficial wounds of dogs…not of people. Those chemicals are specific to the dog only. Licking a wound is a cleansing practice for dogs, and there can be some antibacterial benefit.
That may be OK for scrapes, but it won’t help deeper wounds. If your dog suffers a deep cut or a bite wound, but you don’t think he has to be seen by your veterinarian, it’s best to at least advise your vet of the situation.
When a dog licks a wound, the licking can become excessive and lead to lick granulomas, self-inflicted wounds that can become problematic. Dogs can also become compulsive about licking, and that, too, can become problematic. But anyway, back to the spit.
So, while dog saliva can have some antibacterial benefits to the dog, the same benefits don’t accrue to humans. In fact, dog saliva can actually transmit germs to people. A 2012 study found that dog saliva can transmit bacteria that cause periodontal disease in humans.
That’s kind of funny because dog saliva is slightly more alkaline than human saliva, which is believed to be why dogs suffer far fewer cavities than humans. That alkalinity counters the acidic effect of certain bacteria on dental enamel, causing it to erode.
In addition to germs such as E. coli, salmonella, clostridium and campylobacter, dog kisses can, depending upon where that tongue has been recently, transmit parasites such as roundworms. One study concluded that a puppy can carry from 20 million to 30 million roundworm eggs in its intestinal tract. It’s not uncommon for a dog to have traces of fecal matter in its mouth.
It’s commonly believed that dog hair and dander (shed skin cells) cause allergic reactions in humans. The hair and dander are just the carriers; and you don’t need to involve either the hair or the dander to have an allergic reaction. The allergen is a protein…12 of them, actually…in dog saliva.
After a dog licks a surface and the saliva dries up, the proteins become airborne. So you don’t have to pat the dog, be kissed by the dog, or get his fur on your clothing to have an allergic reaction.
Another interesting fact about dog saliva that I’ve mentioned in previous columns is that it contains no digestive enzymes. Its contribution to digestion is that it lubricates large chunks of food so that they can slide easily down the esophagus into the stomach. Our saliva does contain digestive enzymes that start breaking the food down before it enters the stomach.
OK, so let’s do a reality check. Scads, and maybe even gazillions, of dog kisses are administered to dog lovers every day. Veterinarians and MD’s could probably cite examples of problems. Indeed, one vet in North Carolina said that a child of one of his clients almost lost an eye from a roundworm infection.
But, if you could find statistics on the kiss-to-problem ratio, you’d probably discover the chances of a problem to be minimal. Most experts frown on face kisses, though.