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Ask the Doctor August 2016 Issue

Why Do Cats Drool When They Purr?

Purring and there a connection here?

snuggling cat

You may notice the next time that you’re snuggling with your cat that she fades into a zone of euphoria — and drooling may occur! This is perfectly normal.

Q: Over the years, our family has lived with a number of cats. Each was certainly unique in his or her own way, but quite a few of them shared the same trait: They drooled sometimes while you were petting them.

To clarify, it often appears like drool, but sometimes it’s a single droplet that seems to come from their noses. It’s obviously not a health concern, but just an interesting behavioral thing that I would like to understand better.

- Elaine Best

A: Many cats drool when you are petting them. In the ecstasy of the moment, their eyelids flutter, they purr … and they drool. Why drool, you ask, and that’s a good question. Here’s my theory. When cats are really content, they release “feel good” neurotransmitters in the reward centers of their brain. Endorphins and encephalin are nature’s own morphine-like chemicals that are part of this neurochemical deluge. Endorphins seem to activate the mechanical act of purring.

We have noticed that cats immediately begin to purr when given high doses of opioid painkillers while recovering from painful surgery. The question is, do endorphins also cause salivation, too — and the answer is that they do. If my theory is correct, blocking opioid systems in a cat with a drug like Narcan (naloxone) would abolish this reaction. No more fluttering eyelids, no more purring and no more salivation while being petted until the drug wore off.

But that’s certainly not an experiment I would like to be involved in — so we will just have to leave it as a theory for now. I hope this helps provide some (provisional) rationale for what you have observed.

Nicholas Dodman, BVMS
Professor Emeritus
Tufts University Cummings School of Veterinary Medicine

Comments (1)

Your theory about the chemical basis for purring is interesting, but you didn't really connect that with the drooling behavior. Petting certainly causes the release of endorphins but do endorphins cause drooling or is there something else at play here?

My theory about the drooling? As newborns, kittens are attracted/nudged to their mother's belly (and tits) by the purring of the mother. And what do they do when sucking on a tit? Salivate. At the same time, the mother is also salivating and grooming her newborns. A psychological link is created in this behavior that survives the weening process: as the kittens mature, they start to groom themselves and each other and purring continues as part of that maturation (and is helpful for the females later in life with their own broods). The salivation continues as well (how can one groom yourself without saliva?)

We interject ourselves into this physical/psychological process (the earlier, the better) by adding a human touch - our petting simulates the grooming of the mothers, and thus, because of natal memory, triggers salivation.

Almost all of my cats drool. They show personality tracts in the process. Some drool a little, others drool a lot. Some swallow excessively when petted. Others let it drip out of the corners of their mouths (and their chins get sloppy wet). And others start licking something nearby (usually a hand or fingers or an arm) or even throw back their head and lick in the air. And one of my cats shakes his head like a wet dog would, flinging saliva everywhere (usually on my computer screen). Another cat even starts grooming me, using his teeth to remove (imaginary) tangles in the "fur" of my forearm, wetting everything down as he would his own fur or that of others in his family. And yet another licks my hand for a moment or two, and then rubs his face/head across the wetted area as if I were, or should be, grooming him like his mother did.

Posted by: Mark P | July 30, 2016 8:23 PM    Report this comment

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