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Home > Cats > What Is the Flehmen Response in Cats? Vet Approved Signs, Causes & FAQ

What Is the Flehmen Response in Cats? Vet Approved Signs, Causes & FAQ

Cat with Flehmen's Response

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Dr. Lorna Whittemore

Veterinarian, MRCVS

The information is current and up-to-date in accordance with the latest veterinarian research.

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Cats have a lot of quirky behaviors and expressions that we get used to. If you see your cat sneering at you, it’s not necessarily giving you a dirty look or being judgmental (maybe!), it’s actually a primitive and normal response called the flehmen response.

This facial expression looks like sneering or grimacing in cats, but it’s also common in other animals, including big cats, horses, donkeys, and goats. Our human interpretation of the expression may differ with all of these animals, but as a biological response, it’s identical among them.


What Is the Flehmen Response?

The flehmen response, also known as the flehmen position, flehmen reaction, or flehmening, is a behavior that involves an animal curling back its upper lip and exposing its front teeth, then inhaling. This is named for the Upper Saxon German word, flemmen, which means “to look spiteful,” so it’s no wonder we see it as a sneering expression.

Animals that show the flehmen response often do so when there’s a sight or substance that’s interesting to them. They may hold the position for several seconds and stretch their necks, especially with horses and donkeys.

The Flehmen is seen in many mammals, including domestic cats. Its purpose is to transfer pheromones and other scents into the vomeronasal organ, or Jacobson’s organ, above the roof of the mouth. This happens through a duct that exits just behind the front teeth. So basically, the animal is trying to get a good sniff of whatever is provoking the response.

What Are the Signs of the Flehmen Response?

Animals that show the flehmen response will curl back their top lip, exposing the front teeth and gums. In cats, including tigers and other big cats, this looks like a sneer or another aggressive expression. In horses and other ungulates, it looks more like a silly, mocking expression with their necks long and heads high in the air.

Image By: Stanimir G.Stoev, Shutterstock

What Are the Causes of the Flehmen Response?

As mentioned, the flehmen response pulls air into the vomeronasal organ, an auxiliary olfactory sense organ that these mammals have. This organ is essential for the perception of pheromones and other scents since it’s close to the vomer and nasal bones. In both felines and ungulates, this organ is highly developed.

The ducts that connect the oral cavity to the vomeronasal organ are located behind the front teeth, except in horses. They show a flehmen response, but they don’t have duct communication between the nasal and oral cavities. This is because horses don’t breathe through their mouths. Their vomeronasal organ connects to the nasal passages through a different duct, the nasopalatine duct.


What Is the Purpose of the Flehmen Response?

The flehmen response is a response to something interesting, particularly of odors and tastes. It may be used in intraspecies communication to determine sexual receptivity. In female horses, the flehmen response can indicate reproductive status, and mares will show a more pronounced flehmen response after giving birth.

Some animals show the flehmen response with other species, including non-mammals. Goats were tested for their flehmen response after exposure to urine from multiple species and were shown to recognize a specific pheromone that elicits the response.

In cats, the response is often prompted by another animal in the house expressing its anal glands. These secretions are rich in pheromones, and the cat wants to know where they came from. They’ll also do it around dirty laundry or when they smell urine marking from another cat.

abbyssinian cat meowing
Image By: New Africa, Shutterstock


Frequently Asked Questions (FAQ)

Why Do Cats Do the Flehmen Response?

Like the rest of the mammals that display this response, cats are doing it when they want to analyze a particular scent. This is noticeable with strong odors like urine or anal gland expressions from other animals, soiled human laundry (particularly socks and underwear), and new environments where a lot of animals have been. Cats may also probe their owners to see if they’ve encountered other animals throughout the day.

Does a Sneering Cat Mean It Doesn’t Like a Smell?

The flehmen response may look like the face we make when we smell something bad, but it doesn’t necessarily mean the cat finds the odor offensive. It’s only trying to process the scent more deeply than the nose is capable of, sending signals about it to the brain. Conversely, if a cat doesn’t like a smell, it will try to get away from it

Portrait of cat meowing
Image By: MonaSilver, Pixabay.

Do Humans Have the Flehmen Response?

Humans don’t display a flehmen response. The existence of the Jacobson’s organ in humans has been the topic of debate for some time. The Danish surgeon who discovered it insisted it’s not present in humans, but more recent discoveries suggest that humans may have the Jacobson’s organ as a vestigial organ. More research is needed to understand whether humans use the vomeronasal organ in the same way as other mammals, however.



We often attribute our own familiar human expressions to our pets, especially with cats. We may see the sneer and think that our cats hate us or that something is wrong with them, but it’s perfectly healthy and natural. The flehmen response may look silly, but it’s their way of smelling something deeply and interpreting it.

Featured Image Credit: Jumpstory

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