One of my cat's nostrils runs constantly. The discharge often hardens and blocks it, but is not causing her to sneeze or cough. She is 15 years old and we've lived in the same place for a few years now. Problem first started a few months ago.

My vet said allergies and put her on 5mg prednisolone daily a couple of months ago. The problem has only gotten worse.  Vet had me add Benadryl too a few days ago. No change, below picture is from after work today.

I would have thought allergies would have shown up years ago and affected both nostrils. This problem only ever affects the one, always the same one.  Pollen levels are negligible around here.

Blocked nostril

  • How is your cat? My cat is showing th exact same symptoms. Uni lateral nasal discharge Kind regards Fiona
    – Fi Fi
    Mar 16, 2023 at 18:49
  • I'm sorry, but she died shortly after I posted the above. We never did find out what the problem was. I wish you better luck with your vet adventures.
    – Pascal
    Mar 18, 2023 at 4:41

3 Answers 3


I second the recommendation to take your cat back to the vet for further evaluation.

If there is discharge from both nostrils then it is more likely an upper respiratory infection (viral or bacterial) or allergic problem. If there is discharge just consistently from one nostril then it is very likely there is a problem starting in just that half of the nose. Looking at the discharge, there is almost certainly infection present but coming from one side it is probably secondary to another problem. Possible problems in elderly cat would include growths such as a polyp (which tend to be benign), cancerous growth, or foreign material stuck in the nose. Depending on your location, fungal infections may be considered which can sometimes present as a more unilateral problem.

The other main differential diagnosis – check the teeth! When there is discharge from the nose, it is sometimes easy to assume this is a nose problem, but the roots of the teeth are very close to the nasal cavity. Even if the teeth appear normal from the outside, getting a good set of dental x-rays (under anesthesia obviously) is often a good idea to make sure there are no abscessed roots. A badly infected tooth can progress and drain into the nose, and good news with this in that extraction of the affected tooth will usually solve the problem.

For diagnosis, your cat likely needs some imaging and/or sampling of the nose to be performed. X-rays are usually the most easily accessible and least expensive, but to get good quality skull x-rays sedation is usually needed. To identify more subtle changes advanced imaging such as CT or MRI may be recommended. Rhinoscopy could also be considered in this case (and sometimes a biopsy can be taken this way if needed), although in cats not every practice may do this as it is a small size of endoscope needed.

Please keep us updated on your cat's progress.


You will have to take your cat to the vet for this, get some x-rays of the sinuses and lungs.

Your vet might take a sample of the discharge to see if this is a bacterial or viral infection.

Nasal discharge can be caused by a number of things like a foreign object stuck in the nose of your cat, allergies might cause this, bacterial or viral infection is another cause for this, but then the discharge is often green or brown, sometimes with blood in it.


I give my cat who has asthma a half pill of Zyrtec. She has the exact same thing going on as I am having sinus issues and it really helps her and with her asthma

  • zyrtec is not very helpfull if the cat has an infection,it might even be fatal if an infection goes untreated. Apr 2 at 14:59

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