The most likely reason your cat is congested is a viral upper respiratory infection, the feline equivalent of a cold. Viral infections account for the majority of sudden-onset nasal congestion in cats, with feline herpesvirus and feline calicivirus being the two most common culprits. But congestion that lingers for weeks or keeps coming back can point to other causes, from allergies to growths inside the nasal passage. Understanding what’s behind the stuffiness helps you figure out how urgently your cat needs veterinary attention.
Upper Respiratory Infections: The Most Common Cause
Cats pick up respiratory viruses the same way people catch colds: through direct contact with an infected cat or contaminated surfaces. Feline herpesvirus (FHV-1) and feline calicivirus (FCV) together cause the vast majority of feline respiratory infections. Shelters, boarding facilities, and multi-cat households are hotspots because the viruses spread easily in close quarters. In one study of over 500 cats across different housing environments, herpesvirus was found in up to 59% of cats showing respiratory symptoms, while calicivirus appeared in up to 67% depending on the setting.
A cat with a viral URI typically starts sneezing, develops nasal congestion, and runs a mild fever. You’ll often see watery or thick discharge from the eyes and nose, and your cat may lose interest in food because congestion dulls their sense of smell. Calicivirus infections sometimes cause ulcers on the tongue or inside the mouth, which can make a cat drool or refuse to eat entirely. Mild cases usually resolve in five to ten days, though more severe infections can drag on for up to six weeks.
Bacterial infections frequently pile on after the initial virus damages the nasal lining. When clear, watery discharge turns thick, yellow, or green, bacteria have likely moved in. This secondary infection is what often pushes cat owners to visit the vet, and it’s the stage where antibiotics can actually help (antibiotics do nothing against the underlying virus itself).
Allergies and Environmental Irritants
Allergic rhinitis in cats works much like it does in people. Pollen, dust mites, and mold spores trigger inflammation inside the nasal passages, leading to sneezing, congestion, and a clear, runny nose. Seasonal allergies flare up during high-pollen months, while indoor allergens like dust and mold can cause year-round stuffiness. If your cat’s congestion seems to follow a pattern, appearing at certain times of year or worsening in specific rooms, allergies are worth considering.
Strong scents can also irritate a cat’s sensitive nasal passages. Cleaning products, scented candles, cigarette smoke, and heavily fragranced litter are common triggers. These aren’t true allergies but mechanical irritation, and the congestion usually clears once the irritant is removed.
Chronic Rhinosinusitis
Some cats develop long-term nasal inflammation that never fully goes away. This chronic rhinosinusitis frequently starts after a severe viral infection damages the delicate lining inside the nose and sinuses. Once that lining is compromised, bacteria can repeatedly colonize it, creating a cycle of inflammation, congestion, and thick nasal discharge that flares up over and over for months or even years.
Cats with chronic rhinosinusitis often sound perpetually stuffy. They may snore, breathe loudly, and produce nasal discharge that ranges from clear to greenish. Flare-ups tend to happen when the cat is stressed, has a weakened immune system, or catches a new respiratory bug on top of the existing damage.
Nasopharyngeal Polyps
If your cat is young, typically between eight months and a year old, and the congestion came with noisy breathing or an odd honking sound, a nasopharyngeal polyp is a strong possibility. These are fleshy, noncancerous growths that develop inside the nasal passage or near the eardrum, likely triggered by inflammation from a past respiratory virus.
A cat with a polyp may shake its head, have trouble swallowing, sneeze frequently, or make a startling reverse-sneezing sound as it tries to clear its throat. The congestion tends to affect one side of the nose more than the other. A vet can often diagnose a polyp by sedating the cat and looking behind the soft palate, where the growth appears as a visible pink mass. Polyps are removed surgically, and most cats recover well.
Fungal Infections and Dental Disease
Less common but worth knowing about: fungal organisms can infect a cat’s nasal passages and sinuses. Cryptococcus is the most frequently seen fungal cause in cats, while Aspergillus infections are rare. Fungal infections tend to cause a chronic, progressive nasal discharge, sometimes with visible swelling over the bridge of the nose.
Dental disease is a sneaky source of nasal symptoms. The roots of the upper premolar teeth sit very close to the nasal cavity. When one of these teeth develops an abscess, the infection can spread into the surrounding tissues and mimic a sinus problem. If your cat has congestion that seems concentrated on one side, especially alongside facial swelling near the eye, a tooth root abscess could be the cause. These cases need dental treatment rather than respiratory medication.
Supportive Care at Home
While your cat fights off a mild respiratory infection, a few things can help them breathe more comfortably. Steam is one of the simplest tools: bring your cat into the bathroom while you take a hot shower and let the room fill with warm, humid air for 10 to 15 minutes. This helps loosen thick mucus so your cat can sneeze or clear it out more easily.
Because cats rely heavily on smell to trigger their appetite, a congested cat often stops eating. Warming their food slightly in the microwave (stir it to avoid hot spots) releases more aroma and can coax a reluctant eater. Wet food works better than dry during this time. Gently wiping crusty discharge from around the nose and eyes with a warm, damp cloth also helps keep the airways as open as possible. Make sure your cat stays hydrated; a water fountain or adding water to their food can encourage more fluid intake.
Signs That Need Prompt Veterinary Care
Most mild congestion from a viral infection resolves on its own within a week or two. But certain signs mean your cat needs a vet sooner rather than later:
- Open-mouth breathing or panting. Cats are obligate nose breathers, so breathing through the mouth signals serious distress.
- Rapid breathing rate. If your cat’s sides are visibly heaving or they’re breathing noticeably faster than normal at rest, something beyond a stuffy nose is going on.
- Refusing food for more than 24 hours. Cats can develop dangerous liver problems after just a few days without eating.
- Thick, colored nasal discharge lasting more than a week. This suggests a bacterial infection that may need antibiotics.
- A hunched posture with the head lowered and neck extended. This body language indicates the cat is struggling to move air and may be gagging or on the verge of vomiting.
- One-sided symptoms. Discharge or swelling affecting only one nostril raises the possibility of a polyp, foreign body, fungal infection, or dental abscess.
At the vet, diagnosis usually starts with a physical exam and may include swabs tested for specific viruses and bacteria, imaging of the skull to look at the sinuses and tooth roots, or a scope inserted into the nasal passage under sedation. The right treatment depends entirely on the cause: antiviral support and nursing care for viral infections, antibiotics for bacterial infections, antifungal medication for fungal disease, or surgery for polyps and abscessed teeth.