Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
I am sorry to hear that Coco has this chronic persistant cough. Now an allergy is possible but we do have other potential issues that could cause a cough in an otherwise healthy appearing older cat.
Now since allergies were suggested by her vet, I would say that you could rule this in or out as the root of Coco's troubles by trialling her on anti-histamine treatment. There are a range of antihistamines on the market that can be used with cats. The most common one that we use and find good success with here in the UK is Piriton. Typically this is given at a dose of 1-2 mg up to three times a day (where the standard OTC preparation is 4mg per tablet). We always start this type of treatment off at a low dose since we can see drowsiness (just as in people). Therefore, you might consider trialling her with a quarter or half tablet once to twice a day initially to see if this can allay her cough. Of course, you do want to discuss using this medication with your vet if she is on any other medications you have not mentioned or has any other pre-existing conditions. And if her cough settles with this, then an allergy may be the culprit. That said, if there is no change, then that would be a sign to consider looking into other potential causes for this cough.
In regards XXXXX XXXXX triggers for long term coughing in cats, we have to consider conditions of the upper respiratory tract, the lungs, and the heart.
Coughs associated with the upper respiratory tract usually arise when there is something affecting the airflow through the trachea and down towards to the lungs. This can be due to inflammation if your cat has a flare up for feline herpes virus (as it can cause a tracheitits), a polyp (benign mass growing in the airway), or if there is a more sinister cancerous mass growing there. Cats with these kinds of conditions will sometimes progress to having snoring and voice change or even voice loss as the condition progresses into the later stages. To determine if her cough is upper airway based, the vet would be able listen to her throat region for increased respiratory noise. If this is heard, then they usually will xray region to see if there is a mass or swelling present. Alternatively, if inflammation and a tracheitis is suspected, then feline friendly anti-inflammatories can be trialled.
Coughing that arises from disease of the lung can include chronic bacterial or viral pneumonias (which mild ones can be otherwise be quite subclinical), cancer of the lungs (either primary or spread from another organ), parasitic infections of the lungs, feline asthma and general inflammation of the airway arising from irritation. We can sometimes see it also associated with secondary pulmonary effusion (fluid in the lungs) which can arise with heart issues. Now heart conditions of people and dogs are often associated with a soft cough, this is less the case with cats. So, while it would worth having a vet have a listen to her chest (lungs and heart) to make sure there is no murmur, though this wouldn't necessarily cause a cough.
So, these are what we have to consider with Coco. Since the vet didn't find anything sinister when they last checked her and suspected allergies, do consider a trial on antihistamines to see if this helps. If it doesn't then, we'd have to consider that this could be an early stage hint of one of the above concerns and it may be worth discussing further diagnostics (ie xray) to determine if there is something that is in the early stages of affecting Coco.
I hope this information is helpful.
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All the best,
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