A small amount of clear nasal discharge is normal for cats, but visible snot, especially if it’s thick, colored, or persistent, usually means something is irritating or infecting your cat’s nasal passages. The most common cause by far is an upper respiratory infection, which is essentially a cat cold. Less often, the culprit is allergies, a foreign object, dental disease, or a growth in the nasal passage.
What the discharge looks like, which nostril it’s coming from, and how your cat is acting otherwise all help narrow down the cause.
Upper Respiratory Infections Are the Most Common Cause
The majority of snotty noses in cats trace back to a viral upper respiratory infection. Two viruses cause most cases: feline herpesvirus and feline calicivirus. These spread easily between cats, especially in shelters, multi-cat households, and catteries.
With feline herpesvirus, the pattern is distinctive. It starts with fever, frequent sneezing, and watery eyes, then progresses. The discharge from the nose and eyes begins clear and thin, then thickens over a few days into cloudy, yellow, or greenish mucus. That color change happens when bacteria take advantage of the inflamed tissue and create a secondary infection on top of the virus. Calicivirus looks similar but often includes mouth ulcers and tends to cause less dramatic nasal discharge.
Most cats with a straightforward upper respiratory infection recover within one to three weeks. Kittens, elderly cats, and cats with weakened immune systems are more vulnerable to complications. Once a cat is infected with feline herpesvirus, the virus stays in the body permanently and can flare up during periods of stress, which is why some cats seem to get “colds” repeatedly.
What the Color and Consistency Tell You
Clear, watery discharge is the least concerning type. It’s typical of early viral infections, mild irritation, or allergies. If the discharge turns yellow, green, or thick, that points toward a bacterial component, either a primary bacterial infection or bacteria piling onto an existing viral one.
Bloody discharge is more serious. It can show up with severe infections, but it also raises the possibility of a fungal infection, a foreign body scraping the tissue, or a tumor. Any blood in the nasal discharge warrants a vet visit.
One Nostril vs. Both Nostrils Matters
This is one of the most useful details you can notice at home. Discharge from both nostrils usually points to a widespread process: a viral or bacterial infection, allergies, or something else affecting the entire nasal cavity. Discharge from only one nostril narrows the possibilities significantly. Unilateral discharge is more commonly associated with a foreign body stuck in one nasal passage, a nasal tumor, a fungal infection, or a dental problem where a tooth root has eroded into the nasal cavity.
If your cat has persistent discharge from just one side, that’s worth mentioning specifically to your vet because it changes the diagnostic approach.
Allergies and Environmental Irritants
Cats can develop allergic rhinitis just like people. Pollen causes seasonal flare-ups, while indoor allergens like household dust and mold trigger year-round symptoms. The discharge from allergies is typically clear and thin, accompanied by sneezing. Unlike infections, allergies don’t cause fever or lethargy.
Strong household chemicals, cigarette smoke, scented litter, and air fresheners can also irritate a cat’s nasal lining enough to produce visible discharge. If the snot appeared after you changed cleaning products, litter brands, or started using a diffuser, that’s worth considering.
Foreign Bodies and Dental Disease
Cats who go outdoors sometimes inhale grass blades, seeds, or small debris that lodge in a nasal passage. One study of 77 cats with nasal disease found foreign bodies including grass blades, grass seeds, a stone, and even a needle. The hallmark is sudden, violent sneezing with discharge from one nostril, often starting abruptly in an otherwise healthy cat.
Dental disease is a sneakier cause. The roots of a cat’s upper teeth sit very close to the nasal cavity. When a tooth root becomes severely infected, the infection can erode through the thin bone separating the mouth from the nose, creating a passage called an oronasal fistula. This causes chronic nasal discharge, usually from one side, and your cat may also have bad breath, difficulty eating, or pawing at the mouth.
Growths in the Nasal Passage
Two types of growths can cause nasal discharge: polyps and tumors.
Nasopharyngeal polyps are noncancerous masses that develop most frequently in kittens and young cats, typically between eight months and one year of age. They grow slowly on a slender stalk inside the upper airway, gradually blocking airflow. Signs include noisy breathing, snoring, and nasal discharge that gets progressively worse over months. Polyps are diagnosed by sedating the cat and looking at the back of the throat, where the growth is visible as a pink, fleshy mass. They’re removed surgically and the prognosis is generally good.
Nasal tumors are a more serious possibility, and they’re more common in older cats. They cause sneezing and discharge from one nostril that may become bloody over time. As the tumor grows, it can cause visible facial swelling or deformity. Diagnosis requires a biopsy, since imaging alone can’t confirm the type of growth.
Fungal Infections
Fungal nasal infections are uncommon in cats but worth knowing about. The main culprit is a fungus called Cryptococcus, which causes severe inflammation that can lead to facial swelling, skin ulceration, and discharge that’s usually worse on one side. These infections tend to be chronic and progressive rather than sudden. They require antifungal treatment that can last weeks to months.
Signs That Need Prompt Attention
A cat with a little clear discharge and the occasional sneeze can usually be monitored at home for a few days. But certain signs indicate your cat needs veterinary care sooner rather than later:
- Difficulty breathing or rapid breathing. A resting cat should take no more than 35 breaths per minute. Open-mouth breathing in a cat is always abnormal and urgent.
- Blue-tinged gums or tongue. This signals dangerously low oxygen levels.
- Refusal to eat for more than 24 hours. Cats with stuffy noses can’t smell their food well, which kills their appetite. Cats who stop eating entirely are at risk for a serious liver condition.
- Thick, colored discharge lasting more than a week. This suggests the infection isn’t resolving or there’s a secondary bacterial infection that may need treatment.
- Lethargy. A cat who is withdrawn, hiding, and unresponsive to normal interaction is sicker than a cat who’s just sneezy.
- Any bloody discharge.
- Discharge from only one nostril that persists. This warrants investigation for a foreign body, growth, or dental issue.
What Happens at the Vet
For a straightforward upper respiratory infection, the vet will typically examine your cat, check for fever, and may prescribe antibiotics if a bacterial infection is suspected. Many mild cases resolve with supportive care: keeping nasal passages clear, encouraging eating, and making sure the cat stays hydrated.
If the discharge is chronic, one-sided, bloody, or not responding to initial treatment, the vet may recommend further workup. This can include X-rays (which provide clues but rarely a definitive answer on their own), a scope inserted into the nasal passage to visualize what’s going on, or a nasal flush to dislodge foreign material. When a mass is found during scoping, it’s biopsied, since tissue analysis is the only reliable way to distinguish between a benign growth and a tumor. Bacterial and fungal cultures can identify specific infections that need targeted treatment.
The specific combination of tests depends on your cat’s age, the pattern of symptoms, and how long the problem has been going on. A young cat with sudden one-sided sneezing points the vet toward a foreign body. An older cat with months of worsening one-sided discharge and facial swelling raises concern for a tumor. A recently adopted kitten sneezing with goopy eyes almost certainly has a viral respiratory infection.