Cat Sneezing: When It Is Nothing, and When It Is Not

A cat that sneezes twice, shakes its head and carries on being itself has almost certainly inhaled dust, litter or something you sprayed. That is worth saying first, because most pages on this subject go straight to the frightening list.

What actually needs a vet is different: sneezing that keeps coming back, sneezing with discharge from the nose or eyes, or sneezing alongside a cat that has gone quiet or gone off its food.

The threshold, honestly framed

No institution publishes a hard day count, and we are not going to invent one.

What the sources give is this: uncomplicated upper respiratory infection usually resolves in around 5 to 10 days in mild cases, and can run up to six weeks in severe ones. International Cat Care tells owners to call when the signs on its list appear, rather than to wait out a particular number of days.

So the practical rule: call if it has not stopped after a couple of days, or sooner if anything else joins it.

Why your cat keeps doing this: the part nobody explains

Here is the answer to "why does my cat sneeze every few months", and it is genuinely the thing missing from the pages currently ranking for this.

More than 90% of feline upper respiratory infections are caused by two viruses: feline herpesvirus (FHV-1) and feline calicivirus.

And FHV-1 does not leave. After the first infection, the virus goes dormant in a nerve cluster behind the face and stays there for the cat's life. Stress reactivates it. The published reactivation rates by trigger are strikingly specific:

So the recurring sneezer is usually not catching something new. It is the same virus, surfacing when life gets stressful. That reframes the problem from infection control to stress management, which is a genuinely different conversation with your vet.

Calicivirus behaves differently: it does not go latent in nerve cells the same way, but many recovered cats keep shedding it in saliva for at least 30 days, and some for years.

What vaccines actually do here, stated plainly

This matters and it is routinely fudged.

The 2024 international vaccination guidelines say it outright: there is no herpesvirus vaccine that can prevent infection. Cornell and the European advisory board say the same for calicivirus.

What the core vaccines do is reduce how severe the disease is. That is genuinely worth having, and it is not the same as protection from catching it. A vaccinated cat can still get cat flu, and a page implying otherwise is setting an owner up to think their cat cannot have what it plainly has.

One-sided or both sides? It matters

This is a signal an owner can observe and a vet will actually want.

Both nostrils points towards the viral causes, which affect the whole upper airway.

One nostril only points somewhere else entirely: a foreign body such as a grass seed, a tooth root abscess reaching up into the nasal cavity, a polyp, a fungal infection, or in an older cat, a tumor. The grass scenario is common enough to have its own case series in the veterinary literature; our guide to why cats eat grass covers it from the garden end.

Look at which side the discharge is coming from, and say so when you call.

The rest of the list

• Dental disease. A tooth root abscess can break into the nasal cavity. Common, and rarely mentioned on sneezing pages.
• Bacteria: Chlamydia felis, Bordetella, Mycoplasma.
• Fungal, notably Cryptococcus, which is genuinely a bigger consideration in Australia than elsewhere.
• Polyps and tumors, the latter increasingly with age.
• Allergy. Honestly: allergic rhinitis in cats is much less established than in humans, and our source for it was not independently verified. Treat it as a maybe, not a diagnosis.

Red flags

• A cat that has stopped eating. A blocked nose means no smell, and no smell often means no appetite. That becomes its own emergency quickly.
• Laboured breathing, or a resting breathing rate over 30
• Blood from the nose
• Swelling on the face or around an eye
• Lethargy, or hiding
• Any kitten that is sneezing. Kittens go downhill fast.

Anything that worries you about your cat is a reason to call your vet, and out of hours, an emergency clinic. Nothing on this page is ever a reason to wait.

The lysine question

Lysine supplements are widely recommended online for herpesvirus. Cornell's own position is that the evidence does not support it, and that it may actually worsen viral shedding.

We would rather print that than repeat the popular advice.

If you have more than one cat

Cat flu spreads between cats readily, and a new arrival is the usual route in. That is one more argument for the staged introduction: our guide to introducing cats keeps the new cat in its own room for the first stage anyway, which is quarantine by another name.

What to take away

• A sneeze or two, with a normal cat attached, is dust.
• Call after a couple of days, or immediately if discharge, appetite or energy change.
• Over 90% of cases are two viruses, and one of them stays for life and resurfaces under stress.
• Vaccines reduce severity. They do not prevent herpesvirus infection, and the guidelines say so.
• One nostril rather than two changes the whole list of causes.
• A sneezing cat that stops eating is urgent.
• Lysine is not supported by the evidence.