Is a runny nose an emergency in cats?

Usually not on its own. Clear, watery discharge with a bright, eating cat can often be watched for a few days. Call your vet sooner if the discharge is yellow, green, or bloody, comes from only one nostril, or your cat stops eating or seems tired.

Can a cat's runny nose go away on its own?

Yes. Mild viral upper respiratory infections often clear with basic supportive care like canned food and time in a steamy bathroom. Discharge that lasts more than a week or two, or keeps coming back, needs a vet's workup.

Why is my cat's runny nose only on one side?

One-sided discharge is a meaningful clue. It points toward a localized cause like an inhaled grass blade or other foreign object, a tooth-root infection, a polyp, or a growth, rather than a whole-body virus. It is worth a vet visit.

Illness & Conditions

Your Cat's Runny Nose Has a Color Code. Learn to Read It.

A drippy cat nose is a symptom, not a diagnosis. The color, thickness, and which nostril it comes from tell you whether to wait it out or call the vet.

By Dr. Ravi Mehta, Veterinary Nutritionist

July 18, 2025 · 6 min read

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Here is the mistake almost everyone makes with a drippy cat nose: they treat “runny nose” as the diagnosis. It isn’t. It’s a symptom, and on its own it tells you almost nothing. The useful information is in the details, specifically three of them: what color the discharge is, how thick it is, and whether it’s coming from one nostril or both. Learn to read those three things and you can usually tell the difference between “keep an eye on it” and “call the vet today” from your own couch.

So before you panic about the snot, look at it. Really look.

Start with the color

Nasal discharge in cats is not one substance. It ranges from thin and watery to thick and gluey, and it can be clear, cloudy, yellow, green, or streaked with blood. That range is the whole point, because color roughly tracks with cause.

Clear and watery is the mildest end. It shows up with early viral infections and with allergies, and it usually comes with sneezing, a bit of eye discharge, and an otherwise normal, hungry cat. Cloudy, yellow, or green discharge means pus, which means an infection has set in or a virus has picked up a bacterial passenger. Bloody or blood-tinged discharge is the one that should move fastest up your worry list, because it points toward something more invasive: severe dental disease eating up into the nasal cavity, a fungal infection, a growth, trauma, or a bleeding problem.

“The color of the discharge is doing triage for you before you ever get to the clinic,” says Dr. Ravi Mehta. “Clear and watery in a bright, eating cat can usually wait a day or two. The moment it turns green, one-sided, or bloody, that’s the cat that needs to be seen, not watched.”

Then check the count: one nostril or two?

This is the clue most people skip, and it’s one of the most telling. Discharge from both nostrils generally suggests a whole-body or whole-nose cause, like a virus or environmental allergies. Discharge from a single nostril points to something local and specific on that side.

Curious cats inhale things. A blade of grass, a seed, a bit of litter, and suddenly one nostril is running, the cat is pawing at its face, sneezing hard, and sometimes bringing up a little blood on that side only. One-sided discharge also shows up with a tooth-root infection that has broken through into the nasal cavity, with nasal polyps, and with tumors. None of those fix themselves. If only one side is running, take it seriously.

Behind the color and the count, these are the things that actually make a cat’s nose run.

Upper respiratory infections are far and away the most common, especially in cats from shelters or crowded homes. Most are viral, usually feline herpesvirus or calicivirus, sometimes with a bacterial component like Bordetella bronchiseptica or Chlamydia felis. These often start clear and turn yellow or green as they progress.

Allergies to things in the environment produce thin, clear discharge alongside sneezing, itchy skin, and irritated eyes. Dental disease is an underrated culprit: severe infection below the gumline can burrow up into the nasal cavity and cause thick or blood-tinged discharge, along with bad breath, facial swelling, and a cat who stops eating because chewing hurts. Foreign bodies, as above, tend to be dramatic, sudden, and one-sided. Fungal infections such as Aspergillus come from inhaled spores in plant material or spoiled food and hit immune-compromised cats hardest. Bloody noses can also come from trauma, from bleeding disorders tied to autoimmune disease or cancer, or from rat-bait ingestion. And polyps and tumors, benign or not, can cause chronic discharge and loud, snorting nasal sounds.

What the vet actually does

When you bring in a cat with a persistent runny nose, the vet is essentially doing what you started at home, only with better tools. It begins with a full history and a physical exam. Because a good look inside a sore feline mouth is nobody’s idea of a good time, sedation is often needed, particularly when dental disease is on the table.

Bloodwork checks general health and, crucially for the bloody-nose cats, platelet counts and clotting times to rule out a bleeding disorder. It also gauges anesthesia risk if further procedures are likely. Imaging, either X-rays or a CT scan, lets the vet see tooth roots, skull bones, and sinuses. And when they need to go straight to the source, they can swab or flush the nasal cavity for cytology, looking for cancer cells, inflammatory cells, bacteria, or fungi, or pass a tiny camera up the nose in a procedure called rhinoscopy to hunt for foreign material, tumors, or abnormal tissue, often removing the culprit or taking a biopsy in the same sitting.

Treatment follows the cause, not the symptom

Because a runny nose is a symptom, “treating the runny nose” is the wrong frame. You treat what’s behind it.

Mild viral infections often need only supportive care: canned food to tempt the appetite and boost water intake, and nebulization, which at home can be as simple as sitting with your cat in a steamy bathroom for five to ten minutes to loosen the mucus. Antibiotics come in when a secondary bacterial infection is present. Allergies can’t be cured but can be managed by cutting exposure to triggers like potpourri, cigarette smoke, and dusty litter. Dental disease gets antibiotics, a cleaning, and sometimes extractions. Fungal infections need antifungal medication. Foreign bodies and polyps come out under anesthesia. Cancerous growths may need surgery, radiation, chemotherapy, or some combination. And bleeding disorders are treated based on the underlying cause, often with long-term medication.

When “runny nose” becomes a permanent roommate

Any of these problems, but especially a bad viral infection, can leave a cat with chronic rhinitis, a lasting inflammation of the nasal lining. These cats become lifelong “snufflers,” with symptoms that wax and wane, sometimes for good, and they need ongoing management rather than a one-time fix. It isn’t dangerous so much as persistent, and it’s worth having a plan with your vet rather than reacting to every flare.

What newer research adds

Chronic feline rhinitis has long been one of the more frustrating problems in cat medicine, because once the nasal lining is scarred, no single treatment reliably cures it. Newer work is chipping away at that. A 2025 case series looked at whether routinely culturing the bacteria in cats with chronic nasal disease actually changes treatment, part of a broader push to stop reaching for the same broad antibiotics on every snuffly cat and instead target what’s really growing in there.

Researchers are also building better ways to figure out the cause without going straight to anesthesia and surgery. A 2025 study developed a diagnostic model for feline nasal and nasopharyngeal disease using noninvasive tests, aiming to sort the merely annoying from the serious earlier and with less poking. None of this replaces a vet exam, but it’s a real shift: the field is moving toward matching the treatment to the specific cause, which is exactly what reading the color and the count lets you start doing at home.