Cats Love Earwax

Collation of anecdotes and speculation about why cats like earwax, and human earwax especially.
biology⁠, cats⁠, bibliography
2019-11-052021-06-11 in progress certainty: log importance: 1 backlinks


While petting cats, I accidentally discovered cats are fascinated by the smell & taste of ⁠, particularly that of humans, and this interest can last indefinitely. Dogs & humans, for comparison, are not. A number of anecdotes have reported this over the years, but no formal research appears to have been done on this. What makes earwax attractive to cats? Pheromones? Some nutrient?

Massaging cat ears while petting them, I accidentally discovered that cats can enjoy fingers inserted into their ears, perhaps because, like humans, earwax can build up to uncomfortable levels (and I once discovered undiagnosed in a kitten this way); after testing about 7 cats, I then discovered that cats are fascinated by the smell and taste of their own earwax. (I’m not entirely sure if they exhibit a ⁠, as Kolb 1991 claims. Most of my tests occurred before I learned what a Flehmen response was.) This has held true of most cats I have tested this on. Searching, I’ve found a number of comments in publications and online also noting this phenomenon. There are not many contexts a cat owner would notice cats’ interest in earwax, and many of them are actively discouraged (a cat licking your ear hurts!), but when there is, it appear that earwax interest is often noted. I’ve found that cat earwax is not even the most interesting earwax: cats are more interested in dog earwax, and human earwax most of all: the reaction can be quite strong—given the opportunity, a cat will lick a hearing aid for quite a while, and I’ve had to take away hearing aids from my cats because the intensity of their licking made me worry about them damaging it. Aside from the cost of replacement, this is a safety concern: hearing aids, earphones, or (especially) disposable foam earplugs are small enough to be eaten & endanger cats’ health.

I first thought that it might be like sniffing butts, a way to learn about the health/status of another cat1⁠, but that doesn’t explain why dog & human earwax is more interesting, and cats don’t seem to seek out earwax even after they know about it (with the exception of one of my cats who’d sometimes try to lick my ears when I was in bed)—I find that I sometimes have to touch their noses with a waxy finger before they abruptly become interested (suggesting that whatever the odor is, it doesn’t travel far). Dogs, on the other hand, typically neither appreciate fingers in ears nor show much interest in smelling or licking earwax.

Chemistry

What is it about earwax that fascinates cats? Is there a particular chemical responsible, like a fat or salt or ?2 Earwax in humans comes in ‘dry’ and ‘wet’ forms, differing by race and I would describe cat/dog earwax as being like ‘wet’ human earwax; do cats like ‘dry’ earwax as well? (While there is no shortage of confident assertions that the reason is the “incredibly high concentration of fatty acids and cholesterol” or salt in earwax and similar claims, exactly zero evidence is ever offered for these explanations.)

Anecdotes

Searching Google Scholar/Google⁠, I’ve found the following anecdotes:

  • Arny 1990, “A Craving For Wax”: letter to Nature asking if anyone knew anything after noting

    I dismissed this as a curiosity until I found that our second Siamese cat also liked it. In fact, the second cat leaps on the bed in the morning hoping to be offered some. I mentioned this odd behaviour to 3 other people and have learned from them that their cats also liked the wax.

    I emailed Arny in November 2019, and he said he “got a few replies from people who had noticed the same behavior with their pet.” but otherwise nothing useful.

  • Kolb 1991, “Chapter 25: Animal models for human PFC-related disorders. The Prefrontal Its Structure, Function and Cortex Pathology”⁠, a paper which notes in passing that:

    The most common components of the response pattern include approaching, sniffing, and touching the urine source with the nose, flicking the tip of the tongue repeatedly against the anterior palate behind the upper incisors, withdrawing the head from the urine, and opening the mouth in a gape or ‘Flehmen response’, and licking the nose. This behavioural pattern apparently allows olfactory stimuli to reach the secondary olfactory system, which appears to be specialized to analyse odours that are species-relevant. Cats show this response to urine of other cats, and oddly enough to humans, but they do not show it to urine of rhesus monkeys, dogs, rats, or hamsters. They also do not show it to cat fecal matter or cat fur, although they do show it to cat earwax!

  • 2007, “Augmented Fish Reality”⁠, an interview with an artist who mentions:

    At one time we had 13 cats and 7 dogs. I began being very interested in communications with cats and dogs and the subtle body languages that animals use to communicate. We had a cat named Que tu bu who loved to lick the earwax out of our ears, which was a strange scratchy affair, though clearly a cat showing affection and love toward a human. Later, as a teenager I became interested in Marine Biology…

    Rinaldo also mentioned this in a 2016 essay:

    After minutes of stroking, Catabu would suddenly pop up on his back paws and place his front paws on my shoulder. He would then begin to probe my inner ear with his scratchy tongue. His whiskers tickled as he dug further, licking my ear slowly and deliberately. This was somehow a pleasurable experience, though his tongue was sticky. Cat behaviorists, would speculate he was claiming me as litter-mate. I think we were exchanging love and affection. This was my first trans-species experience. Here was a cat, finding pleasure in the taste of my earwax while we provided mutual affection. This cat/human relationship eft a lasting legacy and deep-probing questions for me about animal-human communication, symbiosis and the contemporary notion of the computer interface.

  • Lynch 2007, “‘No Writer Nor Scholar Need Be Dull’: Recollections Of Paul J. Korshin”⁠, in a memoir of English professor Paul Korshin⁠, recollects:

    At the Osage house, Paul revealed himself as a doting cat lover. He and Debra had adopted brother and sister tabbies he’d named Oscar and Sherwin for his undergraduate mentor at City College. Oscar, the color of an orange creamsicle, would jump into Paul’s lap and purr during the seminars. Paul would cradle him, saying, “He likes to be made much of.” Both cats had free run of his exquisite suits, though he kept lint tape handy to pick up the fur. When Paul met my tuxedo cat Edgar, I mentioned that Edgar was partial to earwax. Intrigued, Paul said, “I don’t know if I have any,” but he put a finger to his ear and allowed Edgar to lick off the spoils. In time, Gaylord and Holly would join Paul and Debra’s cat family. We exchanged Christmas cards over the years “from our cat house to yours.”

On the general Internet, some cat owners have noted this behavior:


  1. The Humane Society of the United States Complete Guide to Cat Care, Christensen et al 2004, notes in its ear cleaning section that with multiple cats who are good friends, it might be unnecessary, because it is a “allogrooming (mutual grooming) task that cats seem to love doing for one another.” Because of social bonding or to learn about each other—or because earwax is interesting & another cat is the easiest source? (I’ve never owned cats which were good enough friends, apparently, to see this for myself.)↩︎

  2. Both butyric acid and salt would also explain the interest in licking sweaty hands/armpits. I tested out the possibility of butyrate on my earwax-loving cat. A 2006 chemistry forum discussion outlined a number of strategies for obtaining butyric acid, of which the second simplest was adding and the simplest was rancid butter. I made rancid butter by putting a few tablespoons of butter into a ziplock bag inside a tupperware and storing it on top of my hot water heater for a week and a half; after a day it had melted and separated into a yellow liquid & a solid white mass, and after a week it smelled bad. I stored it in my refrigerator, and tested my cat three times by offering two saucers of a tablespoon of rancid butter and butter which I heated simultaneously in my microwave for 10s. All 3 times, if he started with the rancid butter, he would eventually lick and eat a little of the rancid butter, but slowly and without enthusiasm, and switch to the fresh butter which he would eat more of and much more enthusiastically, and vice versa, always leaving more of the rancid than fresh. The earwax-style fascination was absent for both kinds of butter. It’s possible that the rancid butter had other breakdown products which offset the appeal of the butyric acid, but I would have expected different behavior if he was simultaneously attracted & repelled. I further tested ‘caramelized butter’ (butter heated up to a point where it browns, which can be sweetened and used as delicious cake frosting); my cat liked it, but another cat I tried was almost indifferent. For a followup experiment, I bought some lye and mixed 2tsp lye with a quarter stick of melted butter (vs another quarter, both left to cool to room temperature), which turned it darker yellow and gave it an odd smell (albeit not nearly as strong as the ‘rotten’ butter smelt) eventually hardened to a cracked white crust, and tried it on my cat; again, he showed no interest in the treated butter compared to the normal ‘fresh’ butter.↩︎