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There are a few animals that will instinctively lick their wounds when injured. SciShow Quick Questions explores the reasons why they do this, and why we sometimes have to stop them from doing it.

Hosted by: Hank Green
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Sources:
https://www.psychologytoday.com/blog/canine-corner/201106/can-dogs-help-humans-heal
http://www.ncbi.nlm.nih.gov/pubmed/19769724
http://www.hindawi.com/journals/iji/2011/367284/
http://www.webmd.com/dvt/blood-clots
http://blog.vetdepot.com/is-it-harmful-for-pets-to-lick-their-wounds
http://www.assisianimalhealth.com/blog/2013/08/why-do-dogs-lick-their-wounds/
http://www.petvet1.com/the-cone-of-shame-a-necessary-evil/
If you've ever lost a fight, physical or verbal, once your opponent wasn't looking, you might have retreated to your corner to lick your wounds. Not literally of course, that's just an expression. Unless of course you're a dog, or a cat, or a small rodent, a horse, or a non-human primate. For all these animals and a few others, literal wound licking is an instinctive response they're born with. When they get hurt, they lick the injury. But vets put cones, sometimes called 'Elizabethan collars' or 'the cone of shame', on dogs or cats to prevent them from doing exactly that. So does it mean that it's bad for animals to lick their wounds, and if it was, why do they do it?

Well, saliva isn't the most sterile substance on the planet but unless they have access to vet care, it's not like they have a bunch of options. Those wild animals and stray cats and dogs are just making the best of a bad situation. Wound licking does have some benefits though, it turns out that the oral mucosa - the mucous membrane that lines the inside of the mouth in humans and animals - typically heals faster than skin. The wound-healing properties of saliva have a lot to do with that. For example, spit has a protein called tissue factor which helps with the blood clotting process. The blood turns from a liquid to a gel, forming a protective covering or scab over an injury, effectively stopping the bleeding. Saliva also has antibacterial properties, specifically the enzyme lysozyme. Lysozyme attacks the cell membranes of certain kinds of bacteria which kills them, helping prevent infection. Also, licking a wound helps an animal to get rid of any extra dirt on it that might lead to an even worse infection.

Great! So why is my vet not letting my dog do its job and lick its wounds? Well if an animal licks a wound a few times after an injury occurs that's fine, but if it keeps going, some pretty gross complications might follow. Tissue damage, inflammation, and infection are just a few of the not so pleasant things that could happen as a result of lots of licking. Inflammation comes in the form of something called a hot spot, which is a red swollen lesion that might appear where an animal has been licking aggressively. Their tongue scrapes the spot again and again until they end up with basically, a scrape.

And while the antibacterial agents found in saliva can be beneficial, animal saliva also contains plenty of bacteria that, while harmless in their mouths, can cause tissue damage or a painful infection if they end up in an open wound. Worse case scenario? If a pet had surgery but didn't have that cone we mentioned to stop them from licking so much, they could end up with dehiscence, where the wound splits open. So if you see a wild animal licking its wounds, well you probably shouldn't interfere -- with any wild animal doing anything. But if your pet dog or cat's doing it, tell them to put their tongue away! It's time to pay the vet a visit. 

Thanks to Patreon patron Jessica from West Virginia for asking this question and thank you to all of our patrons who keep these answers coming, and keep SciShow alive. If you'd like to submit a question to be answered you can go to patreon.com/scishow and if you just wanna keep getting smarter with us, go to youtube.com/scishow and subscribe.