Runny Nose in Cats: Causes and When to See a Vet

A little clear discharge and an occasional sneeze are a different situation from a cat that cannot breathe comfortably or has stopped eating. With a runny nose, the most useful first checks are breathing, appetite and how your cat is behaving, not just the color of the mucus.

Open-mouth breathing, obvious breathing effort or collapse needs emergency veterinary care now. Do not assume a cat is only congested or spend time trying home remedies when breathing is difficult.

Quick Answer

A runny nose in cats can come from a respiratory infection, irritation, inflammation, dental disease or something obstructing the nose. Clear, yellow, green or bloody discharge gives clues but does not identify the cause by itself. Contact your vet if discharge persists or returns, affects one nostril, or occurs with poor appetite, eye problems or reduced energy. Breathing difficulty is an emergency.

What counts as a runny nose?

Nasal discharge is fluid or mucus coming from one or both nostrils. It may be watery, sticky, crusted, blood-streaked or thick enough to partly block the nostrils. Rhinitis means inflammation inside the nose; sinusitis means inflammation in the connected sinuses. Neither term, on its own, tells you what started the problem.

Note whether the discharge began suddenly or has been recurring, whether one or both nostrils are involved, and whether there are eye changes or mouth discomfort. These details often help more than trying to name the illness from a photograph.

How urgent is a cat's runny nose?

• Less concerning, but watch closely: a small amount of clear discharge in a cat that is breathing normally, eating and behaving as usual. Remove obvious airborne irritants and contact your vet if the signs continue, return or worsen.
• Contact your vet promptly: thick or unpleasant-smelling discharge, persistent one-sided discharge, blood, facial swelling, eye discomfort, repeated sneezing, coughing or mouth ulcers. These signs deserve assessment rather than repeated home treatment.
• Call the same day: your cat is not eating, seems markedly subdued, has trouble swallowing, or is a kitten or medically vulnerable cat becoming unwell. Tell the clinic about appetite and drinking when you call.

A fixed three- or five-day waiting period is not a safe rule for every cat. A change in breathing, appetite or alertness matters more than how many days the nose has been running.

When is this an emergency?

Go to an emergency clinic for open-mouth breathing at rest, obvious effort to inhale, blue or grey gums, collapse, or severe weakness with breathing changes. Heavy ongoing nasal bleeding, particularly with weakness or a recent injury, also needs urgent help.

Keep handling minimal and call ahead if possible. Do not hold your cat tightly to inspect the mouth or nose. A noisy, blocked nose and a problem deeper in the chest can both affect breathing; owners should not have to distinguish them before seeking care.

What can cause nasal discharge?

Respiratory viruses and bacterial infections

Feline herpesvirus type 1 and feline calicivirus are important causes of upper respiratory infections, often called cat flu. Sneezing, eye discharge, mouth ulcers, reduced appetite and low energy may occur together. Herpesvirus can remain in the body, with signs recurring during stress or illness.

Bacteria may complicate a viral infection or cause disease in their own right. Bordetella, Chlamydia felis and Mycoplasma do not all produce the same pattern; some are more strongly associated with eye disease. Other bacteria, including Pasteurella, may contribute to secondary infection. A vet selects treatment from the whole picture, not simply because mucus has turned yellow or green.

Chronic inflammation after an infection

Damage to the nasal lining can leave a cat with recurring congestion and discharge even after the original infection has passed. This chronic rhinitis can be difficult to control. Temporary improvement with antibiotics does not necessarily mean a bacterial infection was the only problem.

Irritants and allergies

Smoke, airborne dust, sprays and irritating fumes can trigger nasal inflammation. Allergic rhinitis is also possible, including seasonal or indoor-allergen patterns, but it should not be assumed from clear discharge alone. Persistent signs still need other causes considered.

A foreign object

A grass blade, seed or other material in the nose can cause sudden bouts of sneezing, pawing at the face and discharge, sometimes from just one nostril. Do not probe the nostril with tweezers or try to flush it at home.

Polyps and tumors

Benign inflammatory polyps are particularly relevant in younger cats and can cause snuffling, discharge, swallowing problems or obstruction. Tumors are another cause of persistent or progressive nasal signs, especially in older cats. One-sided or bloody discharge raises concern, but neither proves that a growth is present.

Dental disease

An infected tooth root or an abnormal opening between the mouth and nose can cause nasal discharge. Mention bad breath, chewing changes, a missing tooth or recent dental treatment. A nose problem may need a careful oral and dental examination, not just a respiratory swab.

Fungal infection and injury

Cryptococcus is an important fungal cause in cats; Aspergillus and other fungi are also possible. Persistent discharge, bleeding or swelling over the nose can prompt fungal testing. Treatment depends on which organism is involved and how far the disease has spread.

Falls, bites and other facial injuries can damage the nasal tissues. Tell the vet about any known injury, even if the skin wound looks small.

What can you safely do while arranging care?

Supportive care is for a cat that is breathing comfortably. It does not replace an examination when the signs above are present.

1. Keep the face comfortable. Gently wipe away discharge from the outside of the nose with a soft cloth or pad dampened with warm water. Stop if your cat resists. Do not push anything into the nostrils.
2. Offer familiar food and water. Slightly warming normal wet food can make its smell more noticeable. Make sure it is not hot. Keep water easy to reach and tell the vet if your cat is eating or drinking less.
3. Reduce irritants. Avoid smoke, perfumes, aerosol sprays and strongly scented cleaning products near your cat. Provide a quiet resting area with easy access to food, water and the litter tray.
4. Ask about humidification. Moist air may help loosen secretions in a comfortably breathing cat. If your vet recommends a humidifier or time in a humid bathroom, avoid hot steam and stop if your cat becomes stressed. Never use this to delay care for breathing difficulty.
5. Record useful changes. Note appetite, energy, breathing, discharge from each nostril and any eye signs. A photo may help the vet, but do not restrain your cat or delay urgent care to take one.

Do not give human cold medicines, decongestants, painkillers, antihistamines or leftover antibiotics unless your veterinarian has specifically prescribed the exact product for this cat. Do not put essential oils, vapor rubs or medicated drops in or around the nose.

How will the vet find the cause?

The visit starts with the history and an examination of breathing, eyes, mouth and nose. Tell the vet about contact with other cats, vaccination, travel, previous episodes, existing illnesses, recent procedures and any medicines or household products your cat may have encountered.

Not every cat needs every test. Depending on the findings, the vet may recommend blood tests, selected infectious-disease tests or samples from the eyes, nose or throat. Results must be interpreted with the examination because some cats carry respiratory organisms without those organisms explaining every current symptom.

Persistent, bloody or one-sided signs may need a dental assessment, CT imaging, rhinoscopy, which uses a small camera to examine the nasal passages, or tissue sampling. Fungal testing may be appropriate when the history or examination suggests it. Even with investigation, some cats are diagnosed with chronic inflammation rather than a single removable cause.

How is a runny nose treated?

• Viral illness: supportive care for hydration, nutrition and comfort is central. Selected cats may need antiviral treatment or care for eye complications.
• Bacterial disease: antibiotics may be prescribed when infection is suspected or identified. They do not treat viruses; the choice depends on the suspected organism and your cat's needs.
• Inflammation or allergy: reducing relevant triggers may help. The vet decides whether medication is appropriate after considering infection and other underlying disease.
• Foreign material or a polyp: removal may be needed under sedation or anesthesia, with follow-up to assess healing or recurrence.
• Dental disease: treating the affected tooth or mouth-to-nose opening addresses the source; antibiotics alone may not solve it.
• Fungal disease: antifungal treatment is chosen for the confirmed or strongly supported diagnosis and may require prolonged monitoring.
• Trauma or a tumor: treatment depends on the injury or tumor type. Referral may be needed; surgery is not a universal solution for nasal cancer.

A cat that cannot maintain food or fluid intake, or needs breathing support, may need hospital care rather than a stronger home remedy.

Will it go away, or keep coming back?

Uncomplicated respiratory infections often improve, but there is no recovery deadline that applies to every runny nose. Severe infections, fungal disease, structural problems and chronic rhinitis have different courses. Some cats need ongoing care rather than a permanent cure.

If treatment does not help as expected, or signs return after it ends, arrange a reassessment. Do not restart an old prescription without checking. A new one-sided discharge, bleeding or change in breathing deserves attention even in a cat with a familiar history of cat flu.

Common mistakes to avoid

• Assuming clear discharge must be an allergy or colored mucus must need antibiotics.
• Waiting for a set number of days while appetite or breathing deteriorates.
• Using human cold remedies or medicated nasal products without veterinary instructions.
• Trying to remove an object or flush a nostril yourself.
• Treating every recurrence as the same infection without reassessment.

Can you reduce the risk?

Keep vaccinations up to date with your vet's advice. Vaccination reduces the impact of important respiratory infections but does not prevent every infection or every cause of a runny nose.

If infection is suspected, limit contact with other cats while you seek advice, use separate bowls and wash your hands between handling cats. Let the clinic know about respiratory signs before arrival. Good dental care, less exposure to smoke and dust, and a predictable low-stress routine are useful parts of prevention. Kittens, older cats, flat-faced cats and cats with chronic illness may need closer attention when signs develop.

Frequently asked questions

Can my cat pass a cold to other cats?

Many feline respiratory infections spread between cats, including through contaminated hands or objects. Not every runny nose is infectious, so ask your vet what precautions fit the suspected cause.

Does green mucus mean my cat needs antibiotics?

Not automatically. The vet considers the examination, severity and likely cause. Antibiotics do not work against viruses and will not remove a foreign body or treat a tumor.

Why is only one nostril running?

Local problems such as foreign material, dental disease or a growth are possibilities. Persistent one-sided discharge needs examination, especially if there is blood, odor or facial change.

Can I use a human nasal spray?

Not unless your vet prescribes that exact product for your cat. Human products can contain unsuitable ingredients, and congestion does not identify the cause.

Should I worry if my cat is still eating?

Normal appetite and comfortable breathing are reassuring, but they do not rule out disease. Seek advice for ongoing, recurring, bloody or one-sided discharge, and act immediately if breathing changes.

What matters most

Look beyond the runny nose: comfortable breathing, appetite and energy guide the urgency. Keep a mildly affected cat comfortable while you arrange advice, but do not let home care delay examination when signs persist or your cat becomes unwell.

Sources and further reading

• Cornell Feline Health Center: respiratory infections
• Merck Veterinary Manual: rhinitis and sinusitis in cats
• Merck Veterinary Manual: inflammatory polyps in cats

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