Open-Mouth Panting

The Science Behind It

Dogs pant routinely as their principal cooling mechanism. Cats do not. A cat's normal thermoregulation relies on seeking shade, flattening out on cool surfaces, and spreading saliva over its coat by grooming — evaporation from damp fur does the work that panting does in a dog. A healthy resting cat breathes through its nose, quietly, at somewhere between 16 and 30 breaths a minute, with almost no visible chest movement. Mouth breathing is outside that normal repertoire.

There are three broad reasons a cat opens its mouth to breathe. The first is heat: a cat that has been shut in a conservatory or a car, or exercised hard on a hot day, may pant briefly as a last-resort cooling measure. The second is acute stress or exertion — a car journey, a vet waiting room, or ten minutes of frantic play in an unfit or overweight cat. Both of these should resolve within a few minutes of the cat resting somewhere cool and quiet. The third reason is disease, and it does not resolve.

The Medical Causes

Because cats do not pant casually, mouth breathing is a much stronger red flag in a cat than in a dog. The conditions that produce it include:

• Heart failure — fluid accumulating in or around the lungs, often from undiagnosed hypertrophic cardiomyopathy
• Feline asthma — bronchial constriction, usually with coughing and a hunched, neck-extended posture
• Pleural effusion — fluid in the chest cavity compressing the lungs, from pyothorax, chylothorax or cancer
• Anaemia — too few red cells to carry oxygen, with pale gums
• Heatstroke — a genuine emergency with a mortality rate that rises steeply with delay
• Pain or shock — including after trauma

What to Do

Count the breaths. With your cat resting or asleep, watch the chest rise and fall and count for thirty seconds, then double it. Under 30 is normal; over 40 in a resting cat is abnormal and worth a phone call; over 50 warrants immediate attention. This single number is one of the most useful things an owner can learn to measure, and cardiologists routinely ask owners of cats with heart disease to track it at home.

If your cat is mouth-breathing right now: move it somewhere cool and quiet, do not restrain or chase it, do not force it into a carrier roughly, and telephone a vet before setting off. Stress makes oxygen demand worse, and a cat in respiratory distress can decompensate during handling. If heat is the cause, apply cool — not ice-cold — water to the paws, ears and belly on the way, and keep the car ventilated.

What Not to Confuse It With

Two harmless behaviours can look superficially similar. The flehmen response involves an open mouth with the lips curled back and a glazed expression, held motionless for a few seconds while the cat analyses a scent — it is not accompanied by rapid breathing. And a cat carrying a toy or yowling around a mouthful will obviously have its mouth open. Panting is defined by the rapid, shallow, effortful breathing that goes with it, and often by the neck being extended and the elbows held away from the body.