By Dr Duncan Houston
A new smell is useful information, especially in a cat that usually keeps a clean coat. The first question is where it comes from: the mouth, an ear, the skin, the rear end or the litter tray.
Covering the smell with shampoo or perfume can hide a painful problem. Check how your cat feels and behaves as well as what you can smell.
Quick Answer
Persistent bad odour in a cat can come from dental disease, an infected ear or wound, soiled fur or a toileting problem. The smell alone cannot diagnose kidney disease, diabetes or a urinary infection. Arrange an examination for a recurring or unexplained odour; pain, poor appetite, pus or weakness needs same-day advice, and difficulty urinating is an emergency.
Start by locating the smell
| What you notice | What it means | What to do and when |
|---|---|---|
| Mouth or saliva | Dental disease, oral inflammation or another illness | Book an oral examination; seek same-day care for pain or poor intake. |
| One ear with discharge or scratching | Otitis, mites or an obstructing lesion | Arrange an examination before adding cleaner or drops. |
| A damp, swollen or crusted skin patch | A wound, abscess or skin infection | Contact your vet today, especially if painful. |
| Fur around the bottom | Faecal or urine soiling, impaired grooming or anal sac disease | Check toileting and comfort; persistent soiling needs assessment. |
| Repeated straining with little or no urine | Possible urinary obstruction, whatever the smell | Emergency care now. |
Why can the mouth smell?
Periodontal disease is a common explanation for persistent bad breath. Stomatitis, an oral injury or a mass can also cause odour, drooling and discomfort. Cornell’s guide to bad breath discusses dental and systemic causes. A sweet or ammonia-like smell is a reason to report what you noticed, not a home test for diabetes or kidney disease.
A cat may keep eating despite dental pain. Dropping food, chewing differently or avoiding hard food can be more subtle clues. Cornell’s feline dental guidance explains the importance of assessing painful oral disease.
Skin, ears and the rear end need different care
A bite wound can seal over and later form an abscess that smells strongly when it opens. Thick fur may hide the affected skin. Sore ears need examination for the cause and eardrum status before treatment; the MSD guide to cat ear inflammation advises against home remedies.
Urine or faeces trapped in fur may reflect diarrhoea, leakage, obesity or pain that prevents normal grooming. A brief anal sac smell can happen, but persistent odour with swelling, licking or scooting warrants a check. Severe perianal fistula disease familiar in dogs should not be assumed to be a common feline explanation.
What else should be ruled out?
Diet and recently eaten food can cause transient smells, but repeated foul breath deserves investigation. Strong urine odour can reflect concentration or marking rather than infection. Diarrhoea has many dietary, inflammatory and infectious causes; a particular parasite cannot be identified by its smell. The vet chooses oral, skin, ear, urine or faecal tests based on the location and accompanying signs.
When is this an emergency?
Go immediately if your cat repeatedly strains but produces little or no urine, collapses, cannot breathe comfortably or becomes severely weak. A bad smell with extensive tissue damage, maggots or rapidly spreading swelling also needs urgent care. Do not spend time bathing an unstable cat before transport.
What should you do next?
- Observe the source without forcing the mouth open, squeezing a swelling or probing an ear.
- Record when the smell started, appetite, drinking, grooming and litter tray output. Take a photograph of any visible lesion.
- For a well cat with superficial dirt only, gently clean accessible fur with lukewarm water and dry it. Stop if skin is painful or the cat objects.
- Book an examination if the odour persists, returns or has no obvious harmless explanation. Seek same-day help for pain, discharge or reduced appetite.
Common mistakes
- Masking odour with fragrance, essential oils or repeated baths.
- Diagnosing infection from urine smell and giving leftover antibiotics.
- Squeezing anal sacs or abscesses at home.
- Assuming a senior cat’s reduced grooming is just laziness.
Preventing avoidable odours
Support dental care once the mouth is comfortable, keep litter trays clean and accessible, and help with grooming when mobility limits it. Maintain parasite prevention and a healthy weight. Recurrent soiling needs a plan for the cause, not simply more frequent washing.
Frequently Asked Questions
Why does my cat smell fishy?
Food, anal sac secretions or another source may be responsible. Locate the smell and check for pain, discharge or repeated licking rather than assuming one diagnosis.
Does strong-smelling cat urine mean a UTI?
No. Urinalysis and sometimes a properly collected culture are needed to investigate infection.
Should I bathe a smelly cat?
Only if the problem is simple surface soiling and the cat is comfortable. A wound, painful mouth or infected ear needs specific treatment.
Follow the smell to its source, then let pain, appetite and toileting guide urgency. A targeted examination is more useful than trying to make a sick cat smell clean.
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