Why Does My Cat Have a Runny Nose and Breathe Through Its Mouth?

1 Overview

1. Causes of Runny Nose and Mouth Breathing

A runny nose first suggests an upper respiratory infection — the common ‘cat cold.’ In fact, a cat cold just describes cold-like signs (cough, runny nose, sneezing) from respiratory infection, caused by many agents: mycoplasma, chlamydia, bacteria, calicivirus, and more, all leading to runny nose, congestion, and mouth breathing.

Second, feline rhinotracheitis (cat flu) also causes respiratory infection with runny nose and congestion and mouth breathing. Caused by herpesvirus, it is highly contagious, spreading through secretions and waste to healthy cats; low immunity raises infection risk. In kittens without effective treatment, mortality is very high.

Rhinotracheitis signs also include cough and increased eye/nose discharge, red conjunctiva, swollen eyelids ‘like a walnut,’ and sometimes later mouth ulcers.

2. What to Do

First, have a vet check whether it is a simple upper respiratory infection or rhinotracheitis.

Second, for a simple cold, give a pet cold medicine (e.g., a honeysuckle and Scutellaria tablet); do not use human cold medicine, including children’s, on cats.

For nasal congestion and mouth breathing, try a humidifier to moisten the nose and loosen secretions; if that fails, buy a pet nasal rinse.

If rhinotracheitis is confirmed, follow the vet’s medication plan and isolate the cat to prevent spread. Lysine supplements help boost resistance and reduce recurrence.

The above are only preliminary judgments from these two symptoms. With other signs, consult an online veterinarian or visit a clinic to confirm the cause.