Upper Respiratory Infection (Runny Nose)
The most common cause of a runny nose in cats and dogs is a viral respiratory infection. Vaccines reduce severity but can't guarantee full prevention — most cases recover with supportive home care.
Cats: Viral Upper Respiratory Infection
Feline herpesvirus (FHV-1) and feline calicivirus (FCV) together cause about 90% of feline upper respiratory infections, and most cats have been exposed to FHV-1 at some point in their lives. Common signs after infection include a runny nose (starting clear, becoming thick), sneezing, and eye discharge; FCV can also cause mouth ulcers. The tricky part is that up to 80% of cats infected with FHV-1 become lifelong carriers, some of whom repeatedly flare up and shed the virus during stressful periods (moving, a new pet, hospitalization); FCV carriage usually lasts a few months, with a small number becoming lifelong carriers.
Dogs: Canine Infectious Respiratory Disease Complex (Kennel Cough)
What's commonly called "kennel cough" in dogs is officially canine infectious respiratory disease complex (CIRDC), often caused by multiple pathogens infecting at the same time or in sequence — including Bordetella, canine parainfluenza virus, canine adenovirus type 2, and canine influenza virus — with dogs sometimes infected by two or more pathogens at once. The classic symptom is a sudden, frequent dry cough with a "goose honk" sound, sometimes along with sneezing and watery eyes/nose. It's common in environments where many dogs gather, like boarding, shelters, and daycare; dogs are already contagious before symptoms appear, and it spreads through direct contact, respiratory droplets, and shared toys or bowls.
Can Vaccines Prevent It
Neither the feline FVRCP core vaccine nor the canine kennel cough vaccine can prevent infection 100%, but they significantly reduce severity, shorten the disease course, and lower how much virus is shed — which is why keeping up with core vaccines, even though it can't guarantee your pet never gets a runny nose, is still the most effective prevention available. Other prevention methods: reducing environmental stress and major changes (feline viruses easily flare up under stress), avoiding high-density gathering places, isolating and observing new pets for 1–2 weeks before introducing them, and keeping the environment clean.
Care Tips and When to See a Vet
Most viral infections are managed mainly with supportive home care: keep the area around the nose and eyes clean, increase humidity (spend a few minutes in a steamy bathroom), use strong-smelling food to stimulate appetite, and make sure your pet drinks enough water. Cats that develop difficulty breathing or stop eating entirely for over 3 days need IV fluids at a clinic; dogs whose cough hasn't improved after 10–14 days, or that develop difficulty breathing, severe lethargy, or fever, should also see a vet soon — these can indicate a secondary condition like bacterial pneumonia that needs antibiotics, beyond what a simple viral infection can recover from on its own. A side note: cats are often advised to take L-lysine to ease herpesvirus symptoms, but the veterinary community is divided on this — Cornell University's materials clearly state that multiple studies show little benefit, and it may even worsen viral shedding in some cases. If you're considering it, check with your vet first rather than giving it long-term on your own.
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Sources:
- Cornell Feline Health Center / Cornell Riney Canine Health Center
- VCA Animal Hospitals
- AVMA（American Veterinary Medical Association）
- AAHA（American Animal Hospital Association）
This site is for general reference only and is not a substitute for veterinary diagnosis. If your cat shows unusual signs, please see a vet promptly.