Short answer: if your dog suddenly smells like fish, the cause is almost always the anal glands — two small sacs just inside the rectum that hold a fluid whose smell is genuinely, unmistakably fishy. It is not your imagination, and it is not something your dog rolled in. The other causes are rarer but matter more, and they are covered below.
The fishy smell almost nobody expects: anal glands
Dogs have two anal sacs positioned roughly at four and eight o’clock around the anus. They hold a small amount of oily fluid that normally gets expressed in tiny amounts during a bowel movement — it is a scent marker, the canine equivalent of a signature.
The fluid smells metallic and fishy. When a dog is stressed, frightened, or has soft stools that do not press firmly enough on the sacs, that fluid can be released in larger amounts or build up. Either way, you smell fish.
How to tell it is the glands
- Scooting — dragging their bottom across the carpet or grass
- Licking or biting at the base of the tail or the rear
- The smell arrives suddenly, often after a fright, a car ride, or a vet visit
- A greasy mark left where they were sitting
- The smell is strongest at the back end, not the mouth
A one-off fishy episode after a stressful moment is usually just an expressed gland. It passes. A dog that scoots repeatedly, licks constantly, or smells fishy for days has a gland that is not emptying properly — and that is a vet conversation, not a bath.
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When it stops being a smell and becomes a problem
Anal sacs that do not empty can become impacted, then infected, then abscessed. An abscessed anal gland is painful and can rupture. The progression is not fast, but it is not rare either — small breeds and overweight dogs are more prone to it.
See a vet promptly if you notice: swelling or redness beside the anus, obvious pain when sitting, blood or pus, a dog that yelps when their tail is touched, or persistent scooting over several days.
The other reasons a dog smells like fish
The mouth, not the rear
If the smell follows your dog’s face rather than their back end, look at the teeth. Advanced dental disease produces a foul, sometimes fishy odour, and it is one of the most common untreated conditions in dogs. Check for tartar, red gums, or a reluctance to chew on one side.
Urinary tract infection
A UTI can give urine a strong fishy smell, and a dog that leaks slightly or licks their genitals afterwards carries that smell around. Look for increased drinking, frequent squatting with little output, or accidents in a previously reliable dog.
Skin and ear infections
Yeast and bacterial overgrowth in skin folds or ears produces a musty, sometimes fishy odour. Wrinkled breeds and floppy-eared dogs are the usual candidates. If the smell comes with head-shaking or scratching, start there.
In unspayed females: a genuine emergency
A foul-smelling discharge in an unspayed female, especially a few weeks after a season, can indicate pyometra — a uterine infection that is life-threatening and requires emergency surgery. Combined with lethargy, drinking more, vomiting or a swollen abdomen, this is not a wait-and-see. Go now.
Where is the smell coming from? A quick triage
| Smell strongest at | Most likely cause | What to do |
|---|---|---|
| Rear end, with scooting | Anal glands | Vet if repeated or lasting days |
| Mouth / face | Dental disease | Vet dental check |
| Genitals, with frequent urination | Urinary tract infection | Vet, urine sample |
| Ears or skin folds, with scratching | Yeast or bacterial infection | Vet |
| Discharge, unspayed female | Possible pyometra | Emergency vet, same day |
What not to do
Do not try to express the glands yourself because a video made it look simple. Done wrong, you can bruise the tissue, drive an infection deeper, or cause real pain — and dogs remember. Groomers and vets do this routinely; let them.
Do not just bathe the smell away. A bath removes the odour for a day and leaves the cause untouched. If the smell returns, the bath was never the answer.
Do not assume it will sort itself out if it has lasted more than a couple of days. A gland that is not emptying does not usually start emptying on its own.
Can you prevent it?
Partly. Firm, well-formed stools press on the sacs and empty them naturally, which is why fibre and a healthy weight both help — overweight dogs and dogs with chronically soft stools have anal gland trouble far more often. If your dog is a repeat offender, that conversation with your vet is worth more than any deodorising spray.
Frequently asked questions
Why does my dog smell like fish only sometimes?
Because the glands express under stress. A vet visit, fireworks, a stranger at the door — and out it comes. Occasional and short-lived is normal dog plumbing.
My dog smells like fish but is not scooting. Is it still the glands?
Possibly — not every dog scoots. But check the mouth too, and if the smell persists without any rear-end signs, a vet can narrow it down faster than guessing.
Do female dogs smell fishy more than males?
Both have anal glands, so no. But an unspayed female with a fishy discharge needs ruling out for pyometra, which changes the urgency completely.
Can food cause a fishy smell?
Fish-based diets can affect breath and coat odour mildly. But food does not produce the sharp, distinctive anal gland smell — if it is strong and sudden, do not blame the kibble.
How often should anal glands be expressed?
Most dogs never need it — they manage alone. Routine expression on a healthy dog is unnecessary and can irritate the tissue. It is a treatment for a problem, not maintenance.
The bottom line
A sudden fishy smell from the back end, once, after a fright: normal, annoying, over. The same smell for days, with scooting or licking: the glands need help. A fishy smell from the mouth, or from an unspayed female with discharge: different problem entirely, and the second one is urgent.
This article is general information, not veterinary advice. If your dog seems unwell or in pain, call your vet.