Most sneezing cats have an upper respiratory infection, and most of those are one of two viruses. The Cornell Feline Health Center says up to 97 percent of cats are exposed to feline herpesvirus in their lifetime, and that calicivirus is highly contagious and common. Two bacteria ride along: Chlamydia felis in about one in five cats with these signs, and Bordetella in about one in twenty in crowded places like shelters.
The signs are sneezing, clear or colored discharge from the nose or eyes, red swollen eyes, mouth ulcers, a tired cat, and a cat that stops eating. Herpesvirus brings a fever with it.
Cornell's line is the one owners need: once infected, cats carry herpesvirus for life and may have recurring bouts, set off by stress. A move, a new animal, boarding, a change in the house. The vaccine reduces how sick a cat gets and how much virus it sheds, but it does not prevent infection in every cat. A sneezing cat that has had every shot is not a failed vaccine, it is the way this virus works.
Some cats never fully get over it. International Cat Care explains why: the herpesvirus can permanently damage the lining of the nose and the bone underneath it, and a nose damaged this way is open to bacterial infections that keep coming back. Antibiotics usually make the signs better, but the signs often do not clear completely and may come back after a while. International Cat Care says long-term antibiotic use should be avoided, because it can lead to resistant infections that cannot be treated. For these cats the goal is to control the disease rather than cure it. Merck puts it the same way: long-lasting nose and sinus inflammation is frustrating to manage, and cures are rare.
Herpes is thought to be one of the most common causes, but it is not the only one, so a cat whose sneezing keeps coming back should be checked for the others. International Cat Care lists severe dental disease, where an abscess on a tooth root can reach the nose; polyps; fungal infections; something stuck in the nose, such as a grass seed; allergies; and cancer. Merck adds a sign an owner can see: a cat with a fungal infection of the nose may develop a lump on the bridge of its nose. International Cat Care describes the workup: blood and urine tests, X-rays or a CT scan under anesthesia, a look inside the nose with a small camera, and small tissue samples from inside the nose.
Repeat visits add up. Petipedia's page When you cannot pay the vet bill covers what to ask at the clinic, the nonprofit clinics that charge less, and the charities that help pay.
Merck's list for a dog with sneezing and nasal discharge runs from a viral or bacterial infection, through allergies that come with pollen or stay all year with house dust and mold, to a foreign object, an abscessed root of an upper tooth, a fungal infection, and in older dogs a tumor.
Two patterns matter. A dog that suddenly sneezes violently, paws at its face, and has discharge from one nostril has most likely breathed something in, and a grass seed is the classic. And discharge that starts on one side and spreads to both, or starts as mucus and later carries blood, is the pattern Merck gives for tumors, fungal disease and chronic rhinitis. Both are a vet visit, the first one soon.
The reverse sneeze is a short, rapid inhalation, a snorting fit, that Merck describes as the dog trying to clear its nose. It sounds alarming and is usually over in seconds. If it happens often, film it and show the vet.
Write the date it started and what you saw in the log on My Pet. The vet sheet prints it, and "since Tuesday" beats "recently".
Read 18 September 2026, and 21 September 2026 for the sections on the cat that keeps getting sick.