For curious cat parents
That open-mouth, frozen, slightly offended look has a name: the flehmen response. Your cat is not judging your shoes. They are reading scent information.
The “stinky face” is usually normal cat behavior, not disgust or anger.
Cats use this response to move interesting scent molecules toward Jacobson’s organ.
Common triggers include shoes, laundry, other cats, catnip, litter box smells, and new objects.
You bring home groceries, kick off your shoes, or clean the litter box — and suddenly your cat freezes. Their mouth opens a little. Their upper lip lifts. Their eyes look distant, like they just smelled a secret.
It looks dramatic, but most of the time it is completely normal. That funny “shocked” face is called the flehmen response, sometimes called the cat “stinky face.”
Your cat is not being rude. They are doing a deeper scent check.
What Is the Flehmen Response in Cats?
The flehmen response is a normal scent behavior. A cat sniffs something interesting, pauses, opens their mouth slightly, and may curl the upper lip. To us, it can look like surprise, disgust, confusion, or a tiny sneer.
To your cat, it is more like switching from a regular sniff to a closer chemical inspection.
A shocked little face
Mouth open, lip lifted, blank stare, frozen pause. It can look like your cat just smelled something terrible.
A deeper scent check
They are drawing scent information toward Jacobson’s organ to better read what the smell might mean.
Helpful reference: VCA Animal Hospitals explains that the flehmen response helps pull odors or pheromones toward the vomeronasal organ, also called Jacobson’s organ.
How Does This Weird Cat Face Actually Work?
A regular sniff gives your cat a lot of information. But some smells are worth a second look — especially scents connected to other animals, territory, hormones, or places where another cat has been.
When your cat opens their mouth after smelling something, they are helping scent particles reach a special structure near the roof of the mouth. This is why people sometimes say cats are “smelling with their mouth.” It is not exactly tasting, and it is not exactly normal smelling. It is somewhere in between.
Your cat notices a smell that seems interesting enough to inspect more closely.
They stop moving for a moment and focus on the scent source.
The mouth opens slightly and the upper lip may lift, creating the classic “stinky face.”
Scent molecules move toward Jacobson’s organ, where the cat can gather more chemical information.
Helpful reference: VCA Animal Hospitals describes Jacobson’s organ as an additional scent tool that opens into the roof of a cat’s mouth behind the upper incisors.
Common Smells That Trigger the Cat “Stinky Face”
The flehmen response is not only for obviously bad smells. In fact, your cat may do it around smells that are meaningful, new, or full of animal information.
Your shoes or socks
Shoes pick up outdoor smells, sweat, other animals, grass, pavement, and places your cat has never visited.
Another cat’s scent
If you pet another cat, visit a shelter, or bring home something from a multi-cat space, your cat may inspect the smell closely.
Blankets, laundry, or beds
Fabric holds scent well. Your cat may notice body odor, detergent, another pet, or a new household smell.
Litter box odors
Urine and feces contain strong scent information. A quick flehmen face near the litter area can be normal, especially in multi-cat homes.
Catnip, silvervine, or toys
Some cats make the face around enrichment items, especially if the toy holds scent from plants, saliva, or previous play.
PetMD explains that the flehmen response helps cats process pheromones and hormones through the vomeronasal organ, which is why the behavior often appears around animal-related scents.
Usually Normal. But Not Every Open Mouth Is Flehmen.
A short flehmen response is normal. But if your cat is breathing with an open mouth, drooling, coughing, pawing at the face, vomiting, or acting distressed, that is different.
A short pause, open mouth, then your cat goes back to normal behavior.
Open-mouth breathing, panting, or struggling to breathe.
Drooling, pawing at the mouth, coughing, gagging, or vomiting.
Strong cleaners, essential oils, sprays, or chemicals can be irritating or unsafe.
Sudden distress, repeated symptoms, or possible toxin exposure should be taken seriously.
What Should You Do When Your Cat Makes That Face?
Most of the time, you do not need to do anything. Let your cat sniff, process the smell, and move on. The reaction usually lasts only a few seconds.
Do not punish or scare your cat for sniffing.
Do not shove strong smells toward their face for a reaction.
Keep cleaners, essential oils, and sprays out of paw’s reach.
Keep the litter area clean so strong odors do not build up.
If the smell is from your shoes
Let your cat investigate briefly, then store shoes away if they keep licking or chewing them.
If the smell is from another pet
Give your cat time. Scent is how cats learn who has been in their space.
If the smell is from the litter box
A quick sniff-face can be normal, but a strong litter area smell may mean it is time to scoop, refresh, or rethink the setup. An easy-clean cat litter box can help keep the routine simpler.
If the smell is on paws or fur
For small external messes, you can use pet-safe wipes to gently clean the outside of your cat’s paws or coat. Do not use wipes inside the mouth, nose, eyes, or ears.
Safety note: ASPCA reminds pet parents to be careful with cleaning products and strong household substances around pets, especially cats.
How to Make Your Home More Scent-Friendly for Cats
Cats live in a scent map. They use smell to understand people, pets, objects, rooms, routines, and changes in the home. You do not need to remove every smell. You just want the home to feel readable and safe.
Avoid washing every bed, blanket, and toy at the same time. Cats often like familiar scent on resting areas.
Catnip toys, scratchers, and cat enrichment toys can stay interesting when rotated instead of left out forever.
Try not to place food, water, sleeping areas, and the litter box too close together.
Strong perfumes, air fresheners, and essential oils can be overwhelming to a cat’s sensitive nose.
Helpful reference: ASPCA Animal Poison Control Center notes that cats can be especially sensitive to essential oils and recommends caution around direct exposure.
So Yes, It Looks Funny. But It Is Also Useful.
The flehmen response is one of those cat behaviors that looks silly but serves a real purpose. Your cat is not just reacting to a smell. They are collecting information from it.
The next time your cat opens their mouth after smelling your shoe, another cat’s blanket, or a suspicious corner of the room, you can think of it as a tiny detective moment.
FAQs About the Cat Flehmen Response
Why does my cat open their mouth after smelling something?
Your cat may be using the flehmen response. Opening the mouth slightly can help scent molecules reach Jacobson’s organ, which helps cats analyze certain smells more deeply.
Is the flehmen response normal in cats?
Yes. A short flehmen response is normal cat behavior. It usually lasts a few seconds and your cat should return to normal afterward.
Does the flehmen response mean my cat is disgusted?
Not usually. It may look like disgust, but the behavior is more about scent analysis than emotion.
Why does my cat make that face after smelling my shoes?
Shoes carry outdoor smells, sweat, other animals, and unfamiliar scent information. To your cat, that can be worth a deeper scent check.
Why does my cat smell something and freeze?
Some smells are more meaningful than others. Your cat may pause to process scent information before moving on.
Should I worry if my cat keeps opening their mouth?
A quick flehmen face is normal. But open-mouth breathing, panting, drooling, coughing, vomiting, or distress is not the same thing and should be discussed with a veterinarian.
Can strong scents bother cats?
Yes. Cats have sensitive noses. Strong cleaners, air fresheners, perfumes, and essential oils may be overwhelming or unsafe depending on the product and exposure.
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