Why a Cat Is Sneezing: Causes and When to See a Vet

Sneezing is a protective reflex: the nose expels whatever irritates the lining. So a cat sneezing once or twice after you vacuum, change the litter or open a window means nothing at all. Very different stories hide behind the same sign, and it starts to mean something when sneezing stops being an episode — when it runs for days, comes in bursts, or arrives with nasal discharge, watery eyes or changed breathing.

Why Is My Cat Sneezing: Common Causes

Ranked roughly by how often they turn out to be the answer:

• Upper respiratory infection — by far the leading cause. In cats that means herpesvirus and calicivirus, less often chlamydia or bordetella.
• Environmental irritants — dust, dusty litter, aerosols, perfume, smoke, fresh paint. Here the sneezing is tied to a place and a time.
• Allergic rhinitis — genuinely less common in cats than people assume, and almost never the only sign.
• Dental disease — the roots of the upper teeth sit against the nasal cavity, so advanced periodontitis produces chronic one-sided discharge.
• Foreign body, polyp or tumour — nearly always a one-sided picture in an adult cat.
• Fungal infection of the nose — rare, but stubborn and often with a deformed nasal bridge.

Episode Versus Chronic Rhinitis in Cats

A working rule: an episode lasts hours, a disease lasts days. A cat that sneezed a few times, still eats, still plays, with a clean dry nose, can be watched. A cat sneezing into its third day, with discharge, a changed voice or open-mouth breathing after exertion, is past the watching stage.

Chronic rhinitis is its own category. It runs for weeks and months, fading and flaring, and often follows a viral infection that permanently damaged the turbinates so the nose can no longer clear itself. Such a cat is not cured by a course of anything; the goal is fewer and milder flares.

Herpesvirus and Calicivirus: The Usual Answer

Between them these two viruses account for most of what owners call cat flu. The differences worth knowing:

The key fact: herpesvirus stays for life. The cat recovers, the virus retreats into nerve ganglia and reactivates under stress — a move, a new pet, boarding, surgery. So "the cat is sneezing again six months later" is a flare, not a fresh infection from outside. An indoor-only cat sneezes for exactly the same reason.

If mouth ulcers appear and the cat starts drooling, see drooling in cats.

Cat Nasal Discharge: What the Colour Tells You

Colour is a crude but useful signal:

• Clear and watery — irritation, or the early stage of a viral infection.
• Cloudy, yellow or green — bacteria have joined in. Not a verdict in itself, and not always an antibiotic, but it does warrant an exam.
• Streaked with blood — inflamed, damaged lining; heavy bleeding, or bleeding from one side, is a more serious conversation.
• Thick and one-sided in an adult cat — the most concerning pattern of all.

Both nostrils points to infection or an irritant. One nostril points to an obstruction: a foreign body such as a grass seed, a nasopharyngeal polyp (common in young cats, often alongside ear trouble), or a tumour in an older cat.

Cat Sneezing and Watery Eyes

The nose and the eye are joined by the tear duct, so sneezing and tearing travel together in viral disease. There is a trap here: herpesvirus attacks the cornea as well as the conjunctiva, and a corneal ulcer can cost the eye within a couple of days. If the cat squints, hides the eye from light, or the cornea looks cloudy, read a cat with a watery eye and do not postpone the visit.

Kitten Sneezing Is a Separate Case

The same viruses hit kittens harder: tiny nasal passages, an immature immune system, fast dehydration. A blocked nose means the kitten cannot smell food, so it stops eating, and the circle closes within a day. In kittens from shelters and catteries, sneezing is almost always infectious. If the kitten stops eating, follow the logic in why a cat is not eating: fasting is dangerous in cats by itself.

When to See a Vet Urgently

Go now, do not watch, if any of these are present:

• laboured breathing, belly breathing, extended neck, open mouth;
• bleeding from the nose, especially from one nostril;
• no food for over a day, or over 12 hours in a kitten;
• lethargy, hiding, a low body temperature — see a lethargic cat;
• thick pus from both sides with the eyes gummed shut;
• a deformed nasal bridge or swelling under the eye;
• sneezing together with coughing and wheezing, which moves the problem to the lower airway — see a coughing, wheezing cat;
• weight loss alongside chronic sneezing — a cat losing weight explains why that changes the work-up.

What Not to Do at Home

• No human medicines. Human painkillers and fever drugs are lethal to cats, which lack the enzymes to clear them. Any medication is a vet's decision only.
• No decongestant drops from your own cabinet, and no forceful nasal flushing.
• No leftover antibiotics from a previous prescription: they do nothing against a virus and spoil the bacterial picture.
• No heat packs on the nose and no steam over boiling water — the burn and stress risk outweighs any benefit.
• Do not ignore water intake. With fever and a blocked nose a cat drinks less, and dehydration worsens everything else.

Safe and helpful: switch to a low-dust litter, drop the aerosols, humidify the room, wipe crusts off the nose with a damp pad, warm the food to boost its smell, and reduce stress.

What Tests and Scans Will Clarify the Causes

A short episode needs no work-up. It becomes useful when the sneezing is chronic, one-sided, or comes with systemic signs:

• Complete blood count and biochemistry — inflammation, general condition, kidney and liver function before any prescription. How to read the form: cat blood test.
• A respiratory PCR panel from swabs — answers "which organism".
• X-rays of chest and skull — to rule out pneumonia and assess tooth roots; what a film shows is covered in cat X-ray.
• CT of the nasal cavity — the method of choice in chronic and one-sided disease, since plain nasal radiographs are poorly informative in cats. See MRI and CT in dogs and cats.
• Rhinoscopy with biopsy — when the question is polyp, fungus or tumour.

Sneezing is not a cat-only problem: in rabbits and guinea pigs it is common and dangerous with its own rules — see diseases of rabbits, tortoises and rodents, and what imaging shows in them is in small pet imaging.

If you already hold a lab form, upload it to the pet results interpretation service; a scan or a radiologist's report goes to pet imaging interpretation. If there are no tests yet and you need to understand the picture today, describe the symptoms and get a read on likely causes and urgency.

This article is informational. Diagnosis and treatment of your pet are the job of a veterinarian.