Why Is My Cat Breathing With Their Mouth Open?

By Dr Duncan Houston

A cat breathing with their mouth open may be having a respiratory emergency. If it is happening now, particularly while resting, contact an emergency veterinarian and arrange immediate assessment.

Cats usually breathe quietly through their nose. Open-mouth breathing deserves attention because stress, overheating, airway disease and heart problems can look similar from the outside, yet need very different treatment.

Quick Answer

Open-mouth breathing in cats can occur with severe stress, heatstroke, asthma, heart failure, fluid around the lungs or an airway blockage. Ongoing open-mouth breathing, increased breathing effort, weakness or collapse requires emergency veterinary care. Keep your cat quiet, minimise handling and transport them in a well-ventilated carrier. A brief open-mouth expression after sniffing may be the normal flehmen response, but this should not involve struggling to breathe.

What does abnormal breathing look like?

Respiratory distress means your cat is having difficulty moving air or getting enough oxygen. It is a clinical sign, not a diagnosis.

Watch the chest and abdomen from a distance. Concerning changes include obvious belly movement, rapid shallow breaths, a stretched neck, elbows held away from the chest, or being unable to settle comfortably.

Breathing difficulty can be quiet. Your cat does not need to wheeze, cough or make choking noises for the situation to be serious.

When is open-mouth breathing an emergency?

Emergency: get veterinary care now

• Open-mouth breathing at rest, ongoing panting or obvious breathing effort: these can indicate respiratory distress and need emergency veterinary assessment now.
• Blue-grey or very pale gums, severe weakness, collapse or reduced responsiveness: these may signal a critical oxygen or circulation problem. Go to an emergency clinic immediately.

Do not wait for gum colour to change. Pink gums do not make laboured breathing safe to watch at home. Avoid restraining your cat just to inspect their mouth.

Contact your vet promptly: an episode has stopped or breathing has changed

• A brief panting episode after intense activity or fright that has fully stopped: exertion or stress may be involved, although illness is still possible. Stop the activity and contact your vet for advice, especially if this is new or recurrent.
• Breathing faster than usual while asleep, even with the mouth closed: this may reflect heart, lung or another illness. Contact your vet promptly; increased effort makes it an emergency.

Usually normal: a brief flehmen expression after sniffing

A brief mouth-open expression immediately after investigating a smell, with a relaxed posture and effortless breathing, may be the normal flehmen response. A normal flehmen response needs no treatment. The distinction is explained below; this does not apply to a cat panting or struggling to breathe.

What should you do right now?

If your cat is currently struggling to breathe:

1. Stop activity and reduce stress. Keep children and other animals away. Speak quietly and avoid chasing or repeated handling.
2. Call the nearest emergency clinic. Explain that your cat is open-mouth breathing so the team can prepare.
3. Allow a comfortable position. Do not force your cat onto their side or tightly wrap their chest.
4. Use a secure, well-ventilated carrier. Keep the vehicle comfortably cool and maintain airflow.
5. Do not force anything by mouth. Avoid food, water, tablets or liquid medication during respiratory distress.
6. Leave promptly. A video can help later if someone can record it without delaying care or disturbing your cat.

Stress can worsen breathing difficulties. Your main job is calm, safe transport, rather than trying to identify the exact cause at home.

Do not muzzle a breathless cat or repeatedly pry their mouth open. If your cat has a prescribed emergency plan for an existing condition, follow it while contacting the clinic, without delaying transport.

What should you tell the emergency clinic?

Start with the most important detail: “My cat is breathing with their mouth open.” Say whether it is happening now, when it started, and whether you can see extra chest or belly movement.

Then give any information you already have, without delaying departure to collect it:

• Whether the episode began during sleep, play, travel, a frightening event or heat exposure.
• Whether there has been coughing, an injury, smoke exposure or possible contact with a toxin.
• Your cat’s age and breed, known heart or airway disease, current medicines and any written emergency plan.
• Any recent operation, anaesthetic or veterinary treatment, and which clinic provided it.

This history is useful for kittens, adult and older cats alike. A familiar trigger or a previous diagnosis does not change the need for emergency care if breathing is currently difficult.

Why do cats breathe with their mouths open?

1. Severe stress or exertion

Fear, restraint, travel or intense play can sometimes cause panting. However, a stressful event can also expose an underlying breathing problem.

Stop the activity and contact your vet if panting occurs. If it continues, happens at rest or comes with visible effort, treat it as an emergency. Even a fully resolved episode deserves discussion if it is unexplained or keeps happening.

2. Feline asthma

Asthma causes inflammation, narrowing and mucus accumulation in the lower airways. Affected cats may cough, wheeze, crouch low with their neck stretched forward or breathe through an open mouth during a severe attack.

Repeated coughing can be mistaken for attempts to bring up a hairball. A cat who repeatedly crouches and coughs without producing one needs assessment.

An asthma attack cannot be reliably distinguished from heart or other lung disease by posture alone. Treatment commonly involves medication to reduce airway inflammation and, when appropriate, open the airways. Cornell’s explanation of feline asthma describes why assessment and an individual treatment plan matter.

3. Heart disease and congestive heart failure

Heart disease can cause fluid to accumulate within the lungs or around them, making breathing difficult.

Hypertrophic cardiomyopathy, or HCM, is a common feline heart disease involving thickening of the heart muscle. Some affected cats appear well until complications develop. Rapid breathing, increased effort, lethargy and open-mouth breathing can occur when heart failure develops.

A cat does not need a previous heart diagnosis for heart disease to be a possibility.

4. Fluid around the lungs

Pleural effusion means fluid has collected in the chest space surrounding the lungs. It limits how fully the lungs can expand.

Possible causes include heart failure, infection, cancer, feline infectious peritonitis and leakage of lymphatic fluid. Signs may include shallow rapid breathing, marked abdominal effort and open-mouth breathing.

Identifying fluid is only the first step. Your vet also needs to determine why it accumulated.

5. Overheating or heatstroke

A cat trapped in a hot vehicle, room or other poorly ventilated space can develop heatstroke. Panting may occur alongside drooling, vomiting, weakness, confusion or collapse.

If heat exposure is likely, move your cat into a cooler place and begin gentle cooling with cool tap water over the body, keeping water away from the nose and mouth. Add airflow and contact an emergency vet immediately. Do not wrap them in wet towels or force drinking.

Cooling should begin promptly. Ask the emergency clinic how to manage cooling during transport and when to stop, rather than continuing it automatically throughout the journey. Do not assume every open-mouth breathing episode is heatstroke and start bathing a cat without evidence of overheating.

6. Other airway, lung or whole-body problems

An obstruction, chest injury, pneumonia, lung tumour, smoke inhalation or another serious illness may also cause breathing difficulty. Anaemia can reduce the blood’s oxygen-carrying capacity.

Noisy breathing, nasal discharge, trauma or suspected toxin exposure may help guide the investigation. None provides a safe reason to delay care when your cat is struggling.

Could it just be the flehmen response?

Cats sometimes hold their mouth slightly open after investigating an interesting smell. This is the flehmen response, which helps them analyse chemical signals using a specialised scent organ.

A typical episode follows sniffing, is brief and occurs without forceful chest movement, ongoing panting or distress. Your cat then resumes normal behaviour.

The important distinction is between holding the mouth open to investigate a scent and using an open mouth while struggling to breathe. If you cannot confidently tell the difference, contact your veterinarian.

How to check your cat’s sleeping breathing rate

Only do this when your cat is comfortable. Do not delay emergency care to count breaths.

When your cat is asleep and not purring:

1. Watch the chest rise and fall. One complete rise and fall counts as one breath.
2. Count for 30 seconds.
3. Multiply by two to calculate breaths per minute.

Many comfortable sleeping cats breathe around 15 to 30 times per minute. Repeated readings above 30, or a clear increase from your cat’s usual rate, warrant prompt veterinary advice. Your vet may set an individual threshold for a cat with known disease.

Any increased effort or open-mouth breathing matters regardless of the number.

What should a breathing record include?

For example, 12 complete breaths in 30 seconds equals 24 breaths per minute. Write down the date, time and rate, together with whether your cat was asleep, whether breathing looked easy, and any coughing or change in appetite or activity.

Use the same counting method each time and follow the monitoring plan your vet has given you. A written record is easier to compare than remembering that breathing seemed “a bit fast”. It is for a comfortable cat’s ongoing care, not a reason to wait during an emergency.

What will the vet do?

The first priority is helping your cat breathe. A distressed cat may receive oxygen and minimal handling before a detailed examination.

If fluid around the lungs is restricting breathing, the vet may need to drain it. This can provide relief and allow a sample to be analysed.

Depending on stability and examination findings, investigations may include chest ultrasound, X-rays, blood tests or an ultrasound examination of the heart. Some tests need to wait until your cat can tolerate them safely.

Treatment depends on the cause. Asthma medication, treatment for heart failure, drainage of chest fluid and treatment for infection address different problems. This is why borrowing another animal’s medication or guessing at treatment can be dangerous.

Questions to ask before your cat comes home

• What diagnosis has been confirmed, and what is still being investigated?
• Which medicines should I give, and can you show me how to use any prescribed device?
• What should I record at home, and which change means calling you or returning immediately?
• When is the recheck, and who should I contact outside your opening hours?

Can a cat recover from open-mouth breathing?

Recovery depends on the underlying condition, its severity and how quickly treatment starts.

Many cats with asthma can have good quality of life with ongoing management. Heart disease and conditions causing chest fluid have variable outcomes and may require long-term treatment. The breathing sign alone cannot predict the prognosis.

Even if your cat appears better after resting, explain the episode to your vet. Temporary improvement does not identify the cause or guarantee it will not recur.

Common mistakes to avoid

• Waiting overnight because the cat is still conscious or able to walk.
• Assuming panting must be caused by stress or hot weather.
• Repeatedly handling the cat to check gums, temperature or breathing.
• Giving human medication, leftover antibiotics or another pet’s heart medication.
• Treating repeated coughing as a hairball without an examination.
• Delaying departure to count breaths, record a long video or seek repeated online opinions.

How to reduce future risk

Prevention depends on the diagnosis. Give prescribed treatment consistently and ask for a written plan describing which changes require a call and which require immediate emergency care.

Reduce exposure to tobacco smoke, aerosol sprays, strong fragrances and dusty litter, particularly for cats with airway disease. Keep rooms and travel spaces at comfortable temperatures and avoid trapping cats in poorly ventilated areas.

For cats whose vet recommends home monitoring, record sleeping breathing rates alongside appetite, activity and coughing episodes. Changes over time can be more useful than one isolated measurement.

Keep your regular and emergency clinic numbers somewhere easy to find, and make sure everyone caring for your cat knows where the carrier, medicines and written care plan are kept. Ask your vet about suitable play, enrichment and a calm daily routine as part of your cat’s longer-term care.

Frequently Asked Questions

Is open-mouth breathing ever normal in cats?

A brief flehmen expression after sniffing is normal. Panting can occur after exertion or severe fright, but ongoing, unexplained or recurrent open-mouth breathing needs veterinary assessment. Open-mouth breathing at rest is an emergency.

My cat stopped panting. Do they still need a vet?

Contact your vet and describe what happened. An unexplained or repeated episode needs investigation. If any increased effort, weakness or abnormal behaviour remains, seek emergency care.

Can anxiety cause a cat to breathe through their mouth?

Yes, severe stress can cause panting. However, stress and medical illness can occur together. Do not assume anxiety is the explanation for continued breathing difficulty.

Should I give my cat an inhaler?

Only follow an existing veterinary prescription and emergency plan for that cat. Do not try someone else’s inhaler or assume the problem is asthma. Persistent breathing difficulty still requires emergency assessment.

Can I wait until morning?

Not if your cat is open-mouth breathing, working hard to breathe, weak or unable to settle. Contact an emergency clinic immediately, even if your usual vet is closed.

The key decision: can your cat breathe comfortably?

If your cat is open-mouth breathing at rest or working hard to breathe, contact an emergency clinic and arrange immediate assessment. Keep handling to a minimum and concentrate on calm, safe transport. If an episode has stopped, describe it to your vet rather than assuming that the cause has gone away.

Sources and further reading

• Cornell Feline Health Center: difficulty breathing in cats, including important causes and the need for prompt assessment.
• Tufts HeartSmart: recognising breathing effort and counting breaths, with examples of normal and difficult breathing.
• Ljungvall and colleagues: sleeping and resting respiratory rates in cats, a study of measurements taken by owners at home.
• Cornell Feline Health Center: cardiomyopathy, explaining heart-muscle disease and its complications.
• Merck Veterinary Manual: chest-cavity disorders in cats, including fluid or air around the lungs.
• VCA Animal Hospitals: the flehmen response, explaining the mouth-open expression associated with investigating scent.
• RECOVER first-aid guidelines for dogs and cats, including respiratory distress and heat-related illness.

After veterinary assessment, the ASK A VET™ app offers medication logging and a document library within its Premium plan to help organise ongoing care. A cat struggling to breathe needs immediate in-person veterinary treatment.