# Why Is My Cat Keeping His Mouth Open? Causes to Know If your cat keeps opening his mouth, the meaning depends on what else is happening. Some cats open their mouths briefly while playing, smelling, or relaxing, and that is normal. Other cats hold the mouth open to breathe, which is almost always a sign of a medical problem that needs prompt veterinary care. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - A cat who holds the mouth open while breathing is in trouble. Cats normally breathe through the nose with the mouth closed, so open-mouth breathing at rest is a red flag. - Brief mouth opening during play, yawning, grooming, or a relaxed "chatter" at a bird outside the window is usually harmless. - Mouth pain, nausea, and dental disease can all make a cat sit with the mouth slightly open or drool. - Breathing problems in cats are emergencies. Do not wait to see if it improves on its own. - Never give human pain relievers or any medication to a cat without veterinary direction. Many common drugs are toxic to cats. ## What You Are Seeing: Normal Mouthing vs. a Warning Sign Cats are obligate nasal breathers in most situations. They rely on the nose for airflow, and they usually keep the mouth closed unless they are eating, grooming, vocalizing, or yawning. When a cat holds the mouth open for more than a moment, especially while resting, something is interfering with normal breathing or causing discomfort. ### Normal reasons a cat opens the mouth - Yawning, which is brief and followed by a normal closed-mouth posture - Panting after intense play or heat, which should stop within a few minutes of rest - The open-mouthed "chatter" some cats make when watching prey through a window - A relaxed jaw during deep sleep or while being petted ### Signs that point to a problem - The mouth stays open while the cat is resting or sleeping - Breathing looks labored, with the belly moving in and out strongly - The cat stretches the neck forward to breathe - Drooling, pawing at the mouth, or dropping food while eating - Noisy breathing, coughing, or a change in meow - Blue or pale gums, collapse, or extreme weakness If you see any of the problem signs, treat it as urgent. A cat who is working hard to breathe can tire out quickly. ## Why Is My Cat Keeping His Mouth Open? Main Causes The causes fall into a few groups: breathing problems, mouth and dental disease, nausea, and behavior. The table below gives a quick overview, then each group is explained in more detail. | Cause | Typical clues | How urgent | |---|---|---| | Nasal or airway obstruction | Open-mouth breathing at rest, noisy breathing, discharge, congestion | Emergency | | Heart disease | Open-mouth breathing, weakness, exercise intolerance, murmur, cyanosis | Emergency | | Tracheal narrowing | Progressive open-mouth breathing, coughing, often after intubation | Emergency | | Dental or gum disease | Drooling, bad breath, dropping food, pawing at mouth, bloody saliva | Same-day to urgent | | Oral ulcers or inflammation | Pain when eating, reluctance to chew, weight loss | Same-day to urgent | | Nausea | Lip licking, drooling, vomiting, smacking | Routine to same-day | | Behavioral mouthing | Brief, happens during petting or play, cat is otherwise normal | Routine | ### Breathing problems Open-mouth breathing is the most serious reason a cat keeps the mouth open. In a review of 258 severely dyspneic cats, respiratory causes accounted for 33% of cases, cardiac causes 25%, and both traumatic and neoplastic causes 21% each [1]. Pleural effusion, which is fluid around the lungs, was present in 39% of those cats [1]. That study also found male cats were significantly overrepresented in the cardiac and respiratory groups [1]. Structural problems in the nose and throat can also force a cat to breathe through the mouth. One report described an 8-month-old cat with chronic nasal congestion and open-mouth breathing caused by a congenital palate defect that completely blocked the nasopharynx [2]. Another report described a 6-year-old Siamese cat with a nasal mass that narrowed the left nostril and caused open-mouth breathing at rest [3]. Surgery restored normal breathing in that cat [3]. Heart disease is another common driver. A young cat with a congenital heart defect presented with dyspnea, open-mouth breathing, cyanosis, and exercise intolerance [4]. Cyanosis means the gums and tongue look blue, which signals poor oxygen delivery. Tracheal narrowing can also cause open-mouth breathing. A 12-year-old cat developed progressively worsening open-mouth breathing and coughing after being intubated for a dental procedure [5]. The cause was scar tissue narrowing the windpipe, and a stent relieved the distress [5]. If your cat is breathing with the mouth open and struggling, see our guide to [open-mouthed breathing and respiratory crisis](/knowledge/veterinary-medicine/symptom-guides/why-is-my-cat-breathing-open-mouthed-feline-asthma-respiratory-crisis). ### Mouth and dental disease Gum disease is the most common oral problem in cats [6]. Other causes of mouth inflammation include immune-mediated disease, injuries, chemicals, metabolic disease, burns, tumors, radiation therapy, and infections [6]. Several viruses can inflame a cat's mouth, including feline herpesvirus, feline calicivirus, feline leukemia virus, and feline immunodeficiency virus [6]. Signs vary with the cause and how much of the mouth is affected. Loss of appetite is common, and bad breath and drooling are typical when the mouth or tongue is inflamed [6]. Saliva may be tinged with blood, and pain can make a cat paw at its mouth and resist examination [6]. Lymph nodes in the region may be enlarged [6]. Because oral disease is often hidden and gets worse over time, a complete oral exam should be part of every routine physical [6]. If your cat has mouth odor along with drooling or open-mouth postures, read [why your cat's breath smells](/knowledge/veterinary-medicine/dental-care/why-does-my-cats-breath-smell). ### Nausea Nausea can make a cat lick the lips, drool, and hold the mouth slightly open or smack the lips. This often comes with vomiting, a reduced appetite, or a recent diet change. Nausea itself is not usually an emergency, but repeated vomiting, a cat who will not eat for more than a day, or a cat who seems painful needs a veterinary visit. ### Behavior and petting Some cats open the mouth when petted because they are relaxed, because they are scenting the air, or because they are overstimulated and about to nip. If the cat is otherwise bright, eating normally, and breathing quietly through the nose, this kind of mouthing is not a health concern. Watch for other body language like flattened ears, a twitching tail, or skin rippling, which can mean the petting should stop. ## Red Flags That Make It an Emergency Call an emergency clinic right away if you see any of these: - Open-mouth breathing while resting or sleeping - Breathing that is fast, deep, or obviously effortful - Blue, gray, or pale gums and tongue - A neck stretched forward and elbows held out from the body - Collapse, stupor, or unresponsiveness - Heavy drooling with a swollen face or tongue - A known or suspected toxin exposure - A cat who cannot swallow or is gagging repeatedly A cat in respiratory distress can go downhill within minutes. Do not try to examine the throat at home, and do not force the mouth open. Keep the cat calm, minimize handling, and drive to the nearest emergency hospital. ## What You Can Safely Do at Home While You Wait - Keep the room quiet and dim. Stress makes breathing worse. - Do not chase, restrain, or wrap the cat tightly. - Do not put your fingers in the mouth. A painful cat may bite hard. - Do not give any medication, including human pain relievers. Many are toxic to cats. - Note the breathing rate at rest. Count chest movements for 15 seconds and multiply by four. - Write down when the sign started, what else you see, and any possible exposure to toxins, string, or new foods. - If the cat is stable and this is not an emergency, offer soft, room-temperature food and fresh water. If your cat has been gagging or you suspect something is stuck, see [why your cat was choking](/knowledge/veterinary-medicine/clinical-methods/why-was-my-cat-choking). A cat who is hiding and breathing oddly may be in pain or distress, which is covered in [why your cat is hiding](/knowledge/veterinary-medicine/behavior/why-is-my-cat-hiding). ## What Your Veterinarian Will Check and Test Your veterinarian will start with a full physical exam, including listening to the heart and lungs and checking the gums for color and refill time. They will look at the breathing pattern and may give oxygen before any handling that could stress the cat, since dyspneic cats often cannot tolerate extra diagnostics right away [1]. ### Oral examination A complete oral exam is part of a routine physical because oral disease is best treated early and often stays hidden until it is advanced [6]. Your vet will check the teeth, gums, tongue, and back of the throat. If the cat is painful, this may require sedation. ### Imaging and lab work Depending on findings, your vet may recommend: - Chest X-rays to look at the lungs, heart size, and fluid - Ultrasound to check for pleural effusion or heart changes - Blood work to check organ function, infection, and anemia - CT or endoscopy for nasal, throat, or airway problems, as was used to diagnose palate and tracheal abnormalities in reported cases [2][3][5] - Heart evaluation if a murmur or cyanosis is found [4] ### Treatment Treatment depends on the cause. It may include oxygen, medications for heart or lung disease, antibiotics for infection, dental cleaning or extractions, surgery for masses or narrowing, or a stent for tracheal collapse [5]. Your veterinarian will calculate any medication dose from your cat's weight and health status. ## Prevention and Monitoring - Brush your cat's teeth or use veterinary-approved dental products, and schedule professional dental checks. - Keep vaccinations current, since several viruses can cause mouth inflammation [6]. - Watch for early signs like bad breath, drooling, or dropping food. - Keep string, small toys, and toxic plants out of reach. - Track resting breathing rate at home. A rate that climbs over time can be an early warning. - If your cat has a known heart or airway condition, follow the recheck schedule closely. ## Limitations and When to Contact a Veterinarian This article cannot tell you what is causing your cat's sign. Only a veterinarian who examines your cat can do that. Individual cases need a veterinarian, and the timing matters. Contact a veterinarian the same day if your cat has new drooling, bad breath, pawing at the mouth, dropping food, or a reduced appetite without breathing trouble. Go to an emergency clinic now if your cat is breathing with the mouth open at rest, has blue or pale gums, is coughing persistently, or is weak or collapsing. Schedule a routine visit if the mouth opening is brief, happens only during petting or play, and your cat is eating, drinking, and breathing normally. ## Frequently Asked Questions ### Why does my cat open his mouth when I pet him? Many cats open the mouth briefly during petting because they are relaxed, scenting, or mildly overstimulated. If the cat is breathing quietly through the nose, eating well, and not drooling, this is usually harmless. Stop petting if you see a twitching tail, flattened ears, or skin rippling. ### Why is my cat keeping her mouth open and drooling? Drooling with an open mouth often points to mouth pain, nausea, or dental disease. Gum disease is the most common oral problem in cats, and inflammation of the mouth or tongue commonly causes drooling and bad breath. A veterinarian should examine the mouth, especially if eating has changed. ### Is open-mouth breathing in cats always an emergency? Open-mouth breathing at rest is a serious sign and should be treated as an emergency until proven otherwise. Cats normally breathe through the nose, so mouth breathing usually means the nose or airway is blocked or the cat cannot get enough oxygen. Do not wait to see if it passes. ### Can dental problems make a cat hold the mouth open? Yes. Painful teeth, gum disease, and oral ulcers can make a cat sit with the mouth partly open, drool, or drop food. Oral disease is often hidden and can progress if untreated, so early dental exams matter. A complete oral exam should be part of routine care. ### What should I do if my cat keeps opening and closing his mouth? If the cat is otherwise normal, watch closely for a few minutes and note how often it happens. If the motion comes with drooling, gagging, breathing effort, or a change in appetite, call your veterinarian right away. If the cat is struggling to breathe, go to an emergency clinic immediately. ## Related Articles - [Why Does My Cat's Breath Smell?](/knowledge/veterinary-medicine/dental-care/why-does-my-cats-breath-smell) - [Why Is My Cat Breathing open-mouthed? Feline Asthma & Respiratory Crisis](/knowledge/veterinary-medicine/symptom-guides/why-is-my-cat-breathing-open-mouthed-feline-asthma-respiratory-crisis) - [Why Was My Cat Choking](/knowledge/veterinary-medicine/clinical-methods/why-was-my-cat-choking) - [Why Does My Cat Have Gas?](/knowledge/veterinary-medicine/nutrition/why-does-my-cat-have-gas) - [Why Is My Cat Hiding?](/knowledge/veterinary-medicine/behavior/why-is-my-cat-hiding) - [How To Know If Your Cats Choking](/knowledge/veterinary-medicine/clinical-methods/how-to-know-if-your-cats-choking) - [Why Is My Cat Foaming at the Mouth? Causes and Urgency](/knowledge/veterinary-medicine/emergency-and-first-aid/cat-foaming-at-mouth) - [Why Is My Cat Keeping One Eye Closed? Causes and Care](/knowledge/veterinary-medicine/symptom-guides/why-is-my-cat-keeping-one-eye-closed) - [Why Does My Cat Keep Biting My Legs? Causes and Solutions](/knowledge/veterinary-medicine/behavior/cat-biting-legs-causes) - [Cat Respiratory Infections: Etiology, Clinical Signs, Zoonotic Potential, and Management](/knowledge/bacteria/pet-bacteria/cat-respiratory-infections-etiology-clinical-signs-zoonotic-potential-management) - [Bacterial Respiratory Infections in Cats: Etiology, Clinical Signs, and Treatment](/knowledge/bacteria/pet-bacteria/bacterial-respiratory-infections-cats-etiology-clinical-treatment) ## References 1. [Emergency Dyspnea in 258 Cats: Insights from the French RAPID CAT Study](https://pubmed.ncbi.nlm.nih.gov/40266956/). Veterinary sciences, 2025. 2. [Palatal dysgenesis in a feline causing complete obstruction of the nasopharynx: A case report](https://pubmed.ncbi.nlm.nih.gov/39014910/). Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association, 2024. 3. [Nasal hamartoma causing stenosis and partial obstruction in a Siamese cat](https://pubmed.ncbi.nlm.nih.gov/41168984/). Australian veterinary journal, 2026. 4. [Concurrent Persistent Truncus Arteriosus and Left Atrial Diverticulum in a Domestic Short-Haired Cat](https://pubmed.ncbi.nlm.nih.gov/40150428/). Animals : an open access journal from MDPI, 2025. 5. [Successful management of tracheal stenosis using tracheal stenting in a Russian Blue cat](https://pubmed.ncbi.nlm.nih.gov/39901474/). Journal of veterinary science, 2025. 6. [Disorders of the Mouth in Cats - Cat Owners](https://www.merckvetmanual.com/cat-owners/digestive-disorders-of-cats/disorders-of-the-mouth-in-cats). Merck Veterinary Manual. ## Further Reading - [Merck Veterinary Manual: Cat Owners](https://www.merckvetmanual.com/cat-owners) - [Cornell Feline Health Center: Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information) - [American Veterinary Medical Association: Pet Care](https://www.avma.org/resources-tools/pet-owners/petcare)