What this means
Dogs cool themselves by panting, but cats rarely do, so a cat breathing with its mouth open is almost always in difficulty: it is short of air, or distressed or overheated. The mouth is open, the tongue may show, breathing is fast or laboured, the neck is stretched out, and the cat often sits or lies still and looks anxiously about.
The sign can come from airway, heart or lung disease, and a cat with a short, flat face, whose nose and throat passages are narrow, can show it more easily. Even if the breathing seems to have settled, the vet needs to find what caused it, because breathing problems can come back and get worse.
On the way to the clinic, touch, hold and disturb your cat as little as possible: pressure and stress make breathing harder still. Phone the clinic first, and tell the vet what happened beforehand: play, a fright, heat, a cough, weakness or other changes.
Possible causes
These are things that can cause this sign. It is not a diagnosis, and they are not equally likely for your cat.
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Asthma-like narrowing of the airways
When the small airways become inflamed and narrow, a cat runs short of air and may begin to breathe with its mouth open. A cough or wheeze often comes first.
About the condition: Feline asthma -
The airway shape of a flat-faced cat
In a cat with a short, flat face the passages of the nose and throat are narrow, so it runs short of air more easily. An open mouth is sometimes seen after play, in heat or when excited.
About the condition: Brachycephalic airway syndrome -
Heart disease
When the heart works poorly, fluid can collect in or around the lungs. The cat breathes fast and with effort, sometimes with its mouth open.
About the condition: Heart disease -
Fluid or a growth in the chest
Fluid or a mass in the chest presses on the lungs. The cat may breathe with its mouth open, seem weak and hide.
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Severe stress, heat or overheating
An overheated or frightened cat may begin to breathe with its mouth open. This too is a serious sign that a vet is needed.
What else to watch for
These observations help your vet build the picture faster. Note down what you saw and when.
- Whether the mouth is open while the cat rests, or only after activity or a fright
- Whether breathing is fast or the belly is heaving
- Whether there was recently a cough, a wheeze or another change in breathing
- Whether your cat is flat-faced and has struggled in the heat before
- What colour the gums and tongue are
- Whether it is eating less, hiding or tiring quickly
When to book a routine visit
Open-mouth breathing is an emergency: go to a vet immediately. Even if it was a brief moment after play and your cat is already breathing normally, still phone the clinic the same day and tell them about it.
Related conditions
Conditions whose entries mention this sign. The list is somewhere to read on, not a way to reach a diagnosis.
- Feline asthma Breathing A long-lasting inflammation of the small airways in the lungs. When it flares, the airways tighten and fill with mucus, so air moves in and out with difficulty. It matters because an attack can leave a cat struggling to breathe.
- Brachycephalic airway syndrome Breathing A set of narrowings in the nose and throat of cats with a short, flat face. Pinched nostrils, a soft palate that is too long and other changes get in the way of the air, so breathing takes more work than it should.
- Heart disease Heart A general name for conditions in which the heart can no longer pump blood properly: the heart muscle, the valves or the heart's rhythm can be affected, and some defects are present from birth. In cats heart disease can stay hidden for a long time, so it sometimes comes to light only once it has advanced.