A cat looking funny, surprised or concerned.
Has this funny-looking kitty just had some catnip? Photography by fotostok_pdv/Thinkstock.

What is a Cat Flehmen Response?

The cat flehmen response, a.k.a. the cat stinky face, may look silly or even concerning, but it's actually highly scientific. Let's learn more!
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My incredibly curious cat Merritt (she’s a busy-body calico) is sniffing something again, which isn’t surprising. What is surprising is when she sniffs an object and looks up with her lips curled just slightly back. At first, I thought it was simply a look of concern or surprise over what she had just smelled. But that “cat stinky face” has a scientific name, flehmen, and cats aren’t the only ones who do it. So, what is a cat flehmen response and why does it happen? Let’s take a look. 

What does a cat flehmen response look like?

Cat flehmen response.
A cat flehmen response on my cat, Merritt. Don’t worry — the gift wrap play was completely supervised! Photography by Cait Rohan Kelly.

I’d best describe the cat flehmen response as a look of utter, lip-curling disgust / confusion / concern that elicits some true laugh-out-loud reactions from the cat parents that catch their kitties doing it (see Merritt’s face above during her — supervised and ribbon-less! — prance in our discarded holiday gift wrap). “The flehmen response looks like a cat frozen with her mouth open,” Dr. Sasha Gibbons of Just Cats Veterinary Hospital in Stamford, Connecticut, explains. “Sometimes, cats will roll their lips back over the teeth as well, which can resemble a sneer.”

What is a cat flehmen response?

My cats have some strong opinions and “pooh pooh” at everything from house guests to new toys. But, the cat stinky face isn’t necessarily a snooty sneer — it’s actually way more scientific than that. “The flehmen response is a type of sniffing, but instead of using their nostrils, cats inhale the air through their open mouths,” Dr. Gibbons says.

Anthrozoologist John Bradshaw tells Slate that the flehmen response opens up two small ducts, also known as the nasopalatine canals, on the roof of an animal’s mouth behind the incisors. Those ducts then go through the roof of the mouth and join up with the vomeronasal organ (a.k.a. the Jacobson’s organ), which according to Bradshaw, functions as an auxiliary olfactory bulb of sorts.

Slate also reports that some scientists believe the flehmen response does something that’s between the sense of smell and taste (so cats, sort of DO have a sixth sense!). The ducts contain saliva, meaning that whatever goes in must be voluntarily brought up to the vomeronasal organ. In other words, flehmen isn’t an automatic way to take in smells, as one does through breathing.

The article goes on to explain that cats actually have better vomeronasal organs than dogs. An average house cat has 30 different receptors in that organ, whereas a hound dog has a measly nine.

Why does a cat flehmen response happen?

“Cats use the flehmen response to detect chemical stimuli, such as pheromones, that are present in urine and feces, or areas that cats have marked with scent glands,” Dr. Gibbons says.

But here’s an interesting fact — male cats usually flehmen more than female cats! “Male cats use the flehmen response in relation to mating,” Dr. Gibbons explains. “Scents can help indicate compatibility and if timing is right.”

Of course, there are exceptions to the cat flehmen response, as with my cats. I catch Merritt, my female kitty, displaying a flehmen response to something about once a day. I’ve only seen my male cat, Gabby, flehmen a handful of times in the five years we’ve had him.

Are cats the only ones who display a flehmen response?

Nope! “Along with domestic cats, large cats such as lions and tigers, also use the flehmen response,” Dr. Gibbons tells us. “Outside of the cat family, horses, giraffes, buffalos, goats and llamas have also been seen demonstrating the flehmen response.” Slate reports that humans used to have the vomeronasal organs necessary for a flehmen response — but they got phased out in the evolutionary process. Bummer!

Should you ever be concerned about a cat flehmen response?

Thankfully, the answer is a definite no. “As funny as it may look, there is no harm to a cat exhibiting a flehmen response,” Dr. Gibbons advises. So, enjoy those cat stinky faces (and take some photos — there are not enough good #flehmen pics featuring cats on Instagram!). A cat flehmen response is normal and you have nothing to worry about!

Tell us: Have you ever witnessed a cat flehmen response? Do you have any nicknames for it? What do you think it looks like?

Thumbnail: Photography by fotostok_pdv/Thinkstock. 

This piece was originally published in 2018. 

About the author

Cait Rohan Kelly is a digital writer, editor and marketer with over a decade of experience working with everything from sports stars to different types of cheese. She is currently the Digital Content Marketing Manager for Catster and Dogster. Cait is a lifelong animal lover and cat lady. She lives in Connecticut with her husband (a self-professed cat dude), her son (his first word will probably be one of her cats’ names) and her two rescue cats — Gabby, an orange tabby and avid sleeper, and Merritt, a sassy calico.

Read more about cat behavior on Catster.com:

28 thoughts on “What is a Cat Flehmen Response?”

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  6. Your site is spectacular! I never miss it and this one particularly great!! Love the stinky face article so much!!!
    I enjoy everything! Thank you for making my reading so pleasant and informative!
    Dottie Witmer

  7. Randal Carpenter

    Isni’t that aMAZING…..our beloveds get MORE intriguing by the day and NIGHT! I would also like to add to this phenomenon as a relative side observation, if I may. When cats rub their chinny-chin-chins as a response to findings, their glands leave waxy marks wherever they rub, leaving residual debris from grooming and eating in the process. Your cat may develop feline acne from rubbing his chin upon these frequented spots. Check EVERY WALL EDGE, every furniture with corners or edges for these markings, about 13-15 inches off the floor. They can be wiped off with vinegar quite easily. You will discover many waxy locations throughout your cats territory! Helping reduce his chin residue by helping him clean his chin, will also reduce problems. They can’t reach under their chins!
    Thank you for this excellent article! Randal C.

  8. We call this “deep sniffing”. Now I know what it’s actually called. I come from a long line of cat-people (though we had cats, dogs, rabbits, fish, and hermit crabs growing up)… my parents are 70,just lost both of their cats (to old age), and adopted FIVE NEW CATS if this gives you an idea.

    Anyway, I have 2 cats. One 7 year old with lifelong Bladder Disease and one 9 month old kitten (also from my parents). Both are males.

    This weird, jaw-clicking, deep-sniffing seems to be a “thing” mostly in my older male. The kitten doesn’t do it. But everytime he does it, it’s to obvious things… a weird/odiferous smell or taste & (mostly) hunting on the window sill.

    When my cat sees ferals or outdoor animals he warbles to warn us then does this deep-sniffing with “clicks” that I always wondered about. Now I know it’s largely an ineffective hunting sound or human alarm.

    I don’t recall my cats doing this as a child, so I think it’s connected to cats who are indoor, but are exposed to fresh air (windows) and/or have lots of visual excitement through the windows.

    Its interesting that this has no effect on hunting… but they do it anyway. The Egyptians knew best that these mysterious creatures were special. After many years as a cat-owner… I’m still shocked at how incredible cats really are.

    Now we can retire “clicking” and “deep-sniff” since we know the proper name. Thanks for these excellent articles!

    1. Donna Anderson

      I have a Savannah cat *Dami* When she sniff’s our mouth or some thing she leaves her mouth depends on the smell how far she open her mouth, I have to say, it is CUTE,
      my other two cats dont do that,

  9. My cat on average does this around 3 times a day including when cleaning herself. I used to always think that whatever she smelled must stink really bad. LOL :)

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  12. My cat Elsa, whom I call my “super sniffer,” users her “stinky face” to alert me to a spot inside where one of the three boys has marked. This is extremely helpful since I can’t smell well. (The boys are fixed and only spray when a new, unneutered cat is lurking around outside the apartment, so it’s not an everyday occurrence.)

  13. I adopted a 7lb stray left behind at my apts. when getting cold outside in Nov. Dec. She was only about a year old per my Vet. I had a momma cat and her son who watched thru my patio doors. This little girl Scooter would roll up her lip every time I tried to kiss her cheek or hug her squirmy to be put down. She looked silly so maybe it was my kisses or breath. LOL

  14. My Allie Kat does this when she smells my terrier’s ears! She looks like she is smelling something horrid! I would love to get a pic but it is always a surprise. And now the newest kitten in the Krate does the same thing. Maybe Maggie, the terrier, just stinks!

  15. My cat, Keiki, a Tabby, does this on occasion. It appears that she does this when she wants a more intense scent rather than one more mild through the nostrils. Usually when scenting another cat.

  16. I foster cats and always get concerned when I see this flehmen response because it usually means someone has either peed or marked an area or item. Yikes!

  17. My 18 year old neutered male is a diabetic and does it around the skirting boards in our home when he is having a hypo and is very disorientated, with pupils wide. It is a good indication that I have to take him to hospital immediately. Only happened a couple of times, thank goodness.

  18. I’m sure my cat has done it but since this is the first time hearing about it what “stinky face” is I just never knew when she did it. My cat ‘s good at giving the “evil eye”. What’s the difference?

  19. I often wondered what that was when our female does that. It usually results in a laugh since they look kind of like a very perplexed person when she does it. Maybe it’s her breed but she does it quite often as well.

  20. I’ve always thought the cats look really stupid when they do it. It’s like they’re going “duh?”

    I’ve known its a way of picking up on scents for years, but they still look stupid when they do it!

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  22. Just be sure the inspection and “stinky-face” doesn’t get followed up with something getting sprayed with urine…
    I have three little territorial bottle-raised delinquents who analyze EVERYTHING (including my breath at least once a day) and I live in a moderate fear that one in particular may escalate to spritzing to lay claim to things.

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