Mary Allen
Many people find it unhygienic to be licked by a dog. Doctors in the Middle Ages rightly believed in the healing effects of dog saliva. Nevertheless, the drool is not harmless.
The phrase “licking one’s wounds” is no coincidence: dogs instinctively lick their own body parts, as well as infected parts of humans. The associated idea of the healing effect of dog saliva has survived to this day. In fact, as early as the beginning of the 20th century, researchers BL Hart and KL Powell from the University of California School of Veterinary Medicine discovered that dog saliva can prevent infection by certain bacteria. Bacteria in the wound are greatly diluted by the saliva and most of them are licked out.
Jörg Jores from the University of Bern also knows about the antibacterial components of dog saliva. “Saliva contains lysozyme, which attacks certain bacteria such as staphylococci and streptococci. We also find immunoglobulins there, i.e. antibodies that play an important role in defending against pathogens,” explains the head of the Institute for Veterinary Bacteriology.
Microorganisms are Constantly Changing
Our medieval ancestors probably simply ignored the often strong smell. “Tartar, infections in the pharynx or organic complaints such as those of the kidneys can be the cause of bad-smelling dog saliva and breath,” says Jones. The normal flora of the bacteria present in the saliva does not cause an unpleasant smell. It is difficult to say which bacteria this could be. One only knows that there is an incredibly large amount of bacteria in dog saliva, estimated at several million. “Only very few of us know how to cultivate them.”
However, the sources of the bacteria are known. According to Jones, there is a high level of transmission of bacteria from the bitch to the puppies. In addition, numerous bacteria get into the saliva through food, the environment, and, of course, diseases. The composition of the so-called microbiomes (total of the settled bacteria and other microorganisms) is constantly changing: the dog drinks, eats, licks itself, or licks something and the microbiome is already different. “Antibiotics, a change in diet, conspecifics, and changes in the environment also play a role here,” says Jones. Although most of the bacteria are harmless, infection-causing bacteria can also colonize dog saliva. “As the dog engages in grooming, licking other parts of the body, bacteria like E. coli can be found in the saliva at times.” Escherichia coli can lead to stomach flu or urinary tract infections.
Dangerous, But no Need to Panic
Despite antibacterial and wound-healing components, Jores warns of the dangers that can lurk in dog saliva. Resistant bacteria could also be found there, which can become a problem for humans if they are transmitted. The transmission of rabies viruses is also still an important issue in certain areas – although not in Switzerland.
A certain bacterium can also be dangerous for us: If a person becomes infected with a “dog bite” (Capnocytophaga canimorsus), it can lead to blood poisoning that spreads rapidly. “More than a quarter of all dogs carry this bacterium in their saliva.” The veterinary bacteriologist, therefore, advises caution. “Bacteria like these can be transmitted through open wounds through saliva.”
However, there is no reason to panic. Like many other dog owners, Jores will continue to be happily licked by his beloved four-legged friend. However, he strongly advises older and immune-weakened people against being licked by a dog. Such a pathogen could have devastating consequences for them. And basically, you shouldn’t let your wounds be licked by dogs.