The phrase “to lick one’s wounds” is a metaphor for retiring and recovering after an injury, and certain pets and other creatures exhibit this habit. It’s done by dogs, mice, and even ants. Scratches and scrapes are covered in saliva from a variety of animals. What makes these creatures lick their wounds, though?
The therapeutic benefits of spit, as well as the self-soothing behaviours of licking, are a big part of the answer. According to Dr. Benjamin Hart, a former veterinarian and professor emeritus at the University of California, Davis, wound licking is an innate response refined by natural selection that may relieve discomfort and pain and potentially help injuries heal faster. However, the instinct can easily become counterproductive in dogs and other pets, especially when there are significantly better wound remedies available.
Licking is “the best they probably have” for animals “without thumbs or drugs,” according to Dr. Kristi Flynn, a veterinarian and animal behaviour expert at the University of Minnesota. Licking can help to remove debris from a wound, such as dirt or stray skin, while also reducing discomfort, according to Flynn. It’s similar to rubbing your foot after stubbing your toe or clutching your arm after leaning on a hot stove. “It’s a natural instinct for [animals] to try to comfort an area when they’re in pain,” Flynn told Live Science.
Hart concurred. “Dogs have an instinct to lick wounds that dates back to their wolf progenitor,” Hart told Live Science. “They have a wound; they have an urge to lick it in order to keep it clean and remove the dirt and grime. ” Beyond the immediate attempt to comfort, Hart and others’ research has revealed that the saliva of some animals (including humans) includes antimicrobial and tissue and neuron growth-promoting qualities that aid recovery
According to a 1990 study co-authored by Hart and published in the journal Physiology & Behavior, dog saliva is excellent at killing Streptococcus canis, a type of strep that primarily infects animals, and E. coli germs.
Multiple immunological and cell development proteins particular to dog saliva were discovered in a 2018 study published in the journal PLOS One that compared canine and human saliva. According to a 1979 study in the magazine Nature and a 1991 study in the journal Experimental Gerontology, mouse spit includes chemicals that encourage skin growth and wound repair. According to a 2019 study published in the Archives of Oral Biology, similar growth factors can be discovered in modest amounts in human saliva.
Wound licking, however, can inflict more harm than good in the age of modern medicine for both pets and people. This is why cats and dogs often come home from the clinic wearing a plastic collar. Licked surgical wounds can damage or tear out sutures. Which “turns a minor lesion into a big, enormous problem,” according to Flynn. Excessive licking in dogs is extremely common, and it can hinder injuries from healing. “They make a mountain out of a molehill and lack the discernment to stop,” Flynn explained.
It can also cause the transfer of mouth bacteria onto the infected site.
Saliva does have some antibacterial properties, but it’s not a universal germ killer.
Hart’s 1990 study, for example, discovered that canine spit did not destroy Staphylococcus, a species of bacteria that causes staph infections and is typically found in wounds.