Why Do Dogs Lick Human Wounds?

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A dog's saliva may contain antibacterial medicine.
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"Langue de chien, langue de médecin," the French say: "A dog's tongue is a doctor's tongue." The idea that dog's saliva can help heal wounds is one of those old tales passed from generation to generation, believed by some, disbelieved by others, but never tested. Today scientists are beginning to discover that dog's saliva--and our own--may indeed contain powerful antibacterial medicine.

Licking of wounds

A dog treats his wounds by licking them.
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Anyone who has ever lived with or around dogs knows that when a dog injures itself, it treats its wound by licking it. Nor are dogs the only creatures to do so. Cats--wild and domestic--lick their wounds, as do sheep and many other animals. Most people would admit to having popped a wounded finger in a mouth, at least in their youth.


Putting an injury in the mouth seems intinctual.
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Licking wounds seems an instinctual reaction to the injury: nobody instructs a child to suck a burned finger, and nobody teaches a dog to lick a cut paw. But instinct can be biologically based and often serves a purpose. When a dog licks a wound--or a newborn puppy--it cleans it in much the same way you might clean a counter with a sponge. Recent studies also indicate that licking can protect against infection.



A mother dog protects her puppies from disease by licking them.
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Scientists at the Veterinary School of Medicine at the Univeristy of California at Davis studied canine saliva to determine whether it killed E. Coli and S. Canis bacteria--two of the pathogens that cause infection in new born puppies. They found that it did. By licking her puppies, a mother dog is effectively protecting them against disease.


Pack Instinct

A dog is loyal to its pack.
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Dogs have been domesticated for thousands of years, but they retain the pack instinct that governed their relationships in the wild. Like wolves run in packs, dogs too need to belong to a group. A dog's group includes--and often is limited to--its human family. Since you are part of your dog's pack, it is natural that Fido would want to care for your wounds in the same way it would care for its own.



Do not let your dog clean your injuries.
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Although your dog means well when it tries to lick your wounds, canine saliva can cause infections in humans. As dog bites carry risk of infection, so does licking. It is rare for dog saliva to cause serious injury, but it has in more than one case.