Why Do Cats Hold Their Mouths Open? Understanding Feline ‘Stink Face’

Flehmen reveals your cat’s scents, but a persistently open jaw may call for a vet check.

By Medha deb

Created on Sep 11, 2025

Flehmen reveals your cat’s scents, but a persistently open jaw may call for a vet check.

Why Do Cats Hold Their Mouths Open?

Few things puzzle cat lovers more than seeing their feline companion suddenly stop, stare, and hold their mouth open for several seconds. This strange expressionâa cross between a grimace and a sneerâcan look comical, but itâs rooted in deeply instinctual feline behaviors. Understanding why cats hold their mouths open is key to appreciating their complex communication, and recognizing when it might signal a health problem.

At a Glance: Top Reasons Cats Hold Their Mouths Open

Scent analysis (Flehmen response)
Detecting pheromones or potent odors
Pain mitigation or dental discomfort
Communication, vocalization, and aggression signals
Medical issues (respiratory distress, infection, or trauma)

The Flehmen Response: Catsâ Unique Way of Smelling

The Flehmen responseâsometimes called the âstink faceââis the primary reason most cats momentarily hold their mouths open after sniffing something intriguing. This ancient instinct involves drawing in scents over a specialized olfactory organ to interpret chemical signals in their environment.

When a cat finds an odor interesting, especially pheromones or new scents, it will pause, curl its upper lip, reveal its front teeth, and part its mouth. This open-mouthed moment channels scents up to the vomeronasal organ (also called Jacobsonâs organ), located on the roof of the mouth between the hard palate and nasal cavity.

Key functions of the Flehmen response:

Allows deeper analysis of pheromones (chemical signals between animals)
Often used by males to detect female cats in heat, but all cats can show it
Triggered by especially powerful or unfamiliar odors, including urine, laundry, other animals, and certain foods

Despite their brief, awkward appearance, these episodes can last several seconds, after which the cat returns to its normal pose. Experts emphasize that this response is typically normal and not a sign of illness.

Typical Triggers for the Flehmen Response

Pheromones in urine or gland secretions of other cats
New or especially pungent scents in the home, such as human laundry
Aromatic foods or household chemicals
Odors left by other pets or wildlife, especially on shoes, bags, or doors

Communication and (Silent) Vocalization

Sometimes, cats open their mouths in preparation for communication. This may happen when your cat:

Is about to meow, hiss, growl, or purr
Experiences a silent meow, where the mouth is open but no sound is made
Anticipates making a noise, especially after intense play or as a social cue

This mouth-opening behavior usually lasts only a few moments and is often accompanied by other body language signals such as tail position, ear twitching, or shifting posture. If your cat is otherwise acting normal, this open-mouthed communication is generally harmless and quite common.

Mouth Open as a Sign of Aggression

Another time you might see your cat with its mouth open is during moments of stress, fear, or aggression. Some cats will open their mouths as a precursor to biting, especially during overstimulation (such as prolonged petting). In these cases, other signs usually appear alongside the open mouth, such as:

Growling or hissing
Body tensing or crouching
Rapid tail whipping or flicking
Pinned-back ears
Pupils dilating

If you notice your cat displaying these warning signals, it is wise to give your pet space until it calms down. Open-mouthed aggression is a clear sign that your cat is uncomfortable or feels threatened.

When Is It a Health Problem? Medical Reasons for Open-Mouth Breathing

Although the Flehmen response and communication are usually harmless, there are situations where an open mouth is a red flag for health concerns. Cats are obligate nose-breathers, so persistent open-mouth breathing, sneering, or panting can indicate a serious problem requiring immediate attention.

Potential health causes:

Nasal blockages (due to allergies, infection, inflammation, or nasal tumors)
Dental pain or gum disease, causing the cat to avoid closing its mouth
Respiratory or heart conditions (such as asthma, FIP, pleural effusion)
Severe heat stress or environmental overheating
Acute injury, trauma to the mouth or chest

If your cat is open-mouthed and showing any of the following symptoms, seek veterinary help immediately:

Blue or pale gums (suggesting oxygen deprivation)
Labored breathing, panting, or excessive drooling
Coughing or gurgling sounds when breathing
Head and neck extended, front legs splayed for breathing support
Refusing to move, extreme lethargy, or sudden hiding

Table: Common Causes of Open-Mouth Behavior and Their Meanings

Cause	Typical Signs	Is It Normal?	Action
Flehmen Response	Sniffing, mouth held open a few seconds, grimace, head raised	Yes	Observe, enjoy ‘cat stink face’
Communication	Mouth open before/after vocalizing, may be silent	Yes	No action needed
Aggression/Warning	Growling, hissing, open mouth, tense body	Common in context	Give space, avoid handling
Pain/Dental Issue	Mouth held open, drooling, pawing face, eating difficulty	No	See vet for exam
Respiratory Distress	Open-mouthed panting, labored breathing, blue gums	No	Emergency: Vet immediately
Overheating	Panting after exertion, open mouth	Rare, dangerous if prolonged	Cool down, vet if persists

Pain Mitigation: How Discomfort Affects the Jaw

Cats instinctively keep their mouths slightly open to avoid having sore or inflamed teeth touch each other. Dental pain due to gingivitis, tooth resorption, oral lesions, or injuries can cause a cat to hold its mouth open or drool. This increases airflow across wounds and reduces discomfort.

If your cat displays these behaviors and resists eating, pawing at their mouth, or vocalizing in pain, itâs essential to book a dental exam with your veterinarian as soon as possible.

When Should You Worry?

The vast majority of open-mouthed moments in cats are completely benign. The Flehmen response and communication do not require any intervention. However, persistent open-mouth breathing, panting, or signs of distress must never be ignored.

If your cat is drooling, lethargic, or open-mouth breathing for more than a few minutes, call your veterinarian.
If blue or pale gums, wheezing, or refusal to move appear, treat this as an emergency.
Regularly examine your catâs gums, teeth, and nose for signs of redness, swelling, bleeding, or blockage.
If in doubt, it is always best to check with a professionalâcats are very good at masking early signs of illness.

Frequently Asked Questions (FAQs)

Q: Why does my cat hold its mouth open after sniffing something?

A: This is usually the Flehmen response; your cat is directing interesting odors to a special organ used for sensing pheromones. Itâs normal and part of feline scent analysis.

Q: Should I ever worry if my cat is sitting with its mouth open?

A: Brief, relaxed open-mouthed episodes are common, but if your cat seems distressed, drools, or struggles to breathe, consult a vet immediately. Persistent open-mouth breathing is often a sign of illness or pain.

Q: Do all cats show the Flehmen response?

A: Yes, any cat can display the Flehmen response, though it’s most common in mature, especially male, cats exposed to pheromones or new, potent smells.

Q: Can play, stress, or exertion cause my cat to pant or hold its mouth open?

A: Rarely, after intense exercise or acute stress, a cat may briefly pant. If your cat recovers within a few minutes and shows no other symptoms, monitor but do not be alarmed. If panting persists, or is accompanied by other symptoms, seek prompt veterinary advice.

Q: What should I do if my cat is drooling or refuses to close its mouth?

A: Mouth discomfort or dental issues may be the cause. Schedule a dental exam and vet checkup promptly to avoid further complications.

Tips for Protecting Feline Health

Monitor your catâs breathing habits, especially after activity or exposure to new environments.
Keep up with regular dental checks and cleaning to prevent oral pain.
Avoid exposing cats to harsh chemicals or unfamiliar animal scents that might cause anxiety or stress.
Learn to recognize stress signals and body language to preempt aggression or fear-related behavior.
Always have fresh water, cool resting spots, and easy access to veterinary care available in case of overheating or emergencies.

Bottom Line

For most cats, holding the mouth open is a fascinating display of their extraordinary sense of smell and subtle communication system. In rare cases, however, this behavior can be a vital clue that a medical issue needs urgent attention. By watching closely, learning the different causes, and responding quickly to concerning signs, you can ensure your feline friend enjoys both curiosity and good health.

References

Author

medha deb

Medha Deb is an editor with a master's degree in Applied Linguistics from the University of Hyderabad. She believes that her qualification has helped her develop a deep understanding of language and its application in various contexts.

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