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? 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.