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The Flehmen Response: Why is my cat making that face?

Updated: Jul 10, 2023

Has your cat ever smelled something and then immediately made a repulsed, confused, or just downright weird face? As a cat owner we may see our feline’s reaction and assume this is a sign of aggression, or that perhaps they felt something along the lines of disgust or repulsion. In actuality, the science behind this phenomenon reveals this behavior is perfectly natural and healthy in cats!

What It Is:

Often called the “Flehmen response”, cats will lift their lips and may tilt their heads back. The word Flehmen is German for “lip curl”, and cats will do just this in order to better investigate a smell. This allows two ducts on the roof of the cat’s mouth to open up. Cats use the scent hormones called pheromones to send messages to other cats, such as rubbing their cheeks against objects to mark their territory. When a cat grimaces or lifts its lips, pheromones are trapped by its tongue and then transferred to the two ducts in its mouth.

The flehmen response is essentially sniffing, but cats inhale air through their mouths instead of their noses. The ducts connect to the vomeronasal organ, also called the Jacobson’s organ- this is an organ us humans have inside of us too. Jacobson's organs are located between the hard palate of the mouth and the septum of the nose. They are linked to the hypothalamus, the part of the brain that transfers information to different locations. Because cats do this, scientists believe that the information the Jacobson’s organ processes may be in between taste and smell, and cats could be using it not only to determine a female’s reproductive status, but the physiological conditions of an animal as well.

Do All Cats Do This?

Yes, all cats do this! However, male cats tend to show the flehmen response more often. This is thought to be because they pay more attention to sex-related information, even if neutered, and scents left by another cat can indicate whether a female cat is a compatible mate. However, the sneer is not exclusive to males. Many owners have reported their female kitty doing this multiple times a day, whereas their male cat only does it on rare occasions.

Why It Matters:

The flehmen response is completely normal for your cat to do and does not call for concern. It helps with mating, communicating with other cats, as well as marking their territory. For example, when cat sitting in San Francisco I’ve had cats warily approach me and show the flehmen sneer because I’ve been spending time around other people’s cats. Recognizing whether your furry friend is panting, hissing, or flehming is an important distinction when interpreting your cat’s behavior (plus, now you know more about why your cat always makes that funny face).

The flehmen response is found in many other animals as well, such as horses, giraffes, elk, and llamas. During the evolutionary process, even humans had it! In fact, when a human baby is born it develops a pair of pits at the bottom of the nostrils, a sign that the ducts used to connect to the vomeronasal organ- evidence that during development our ancestors definitely flehmed.


-Rohan Kelly, Cait. “What Is a Cat Flehmen Response?” Catster, 14 May 2019,

-Cornwell, Langley. “What Is a Flehmen Response in Cats?” CANIDAE, 27 May 2015,

-Bittel, Jason. “Why Do Dogs, Cats, Camels, and Llamas Make That Weird Face?” Slate, 12 Jan. 2016,

-Shojai, Amy. “What Is the Flehmen Response in Cats?” The Spruce Pets , 12 Jan. 2020,


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