The most likely reason your dog’s private area smells like fish is their anal glands. Dogs have two small sacs sitting just inside the anus, at roughly the 4 and 8 o’clock positions, that produce a pungent, oily secretion. This fluid contains compounds like trimethylamine (the same chemical responsible for the smell of rotting fish) along with sulfur compounds and various esters. Normally, a small amount squeezes out during bowel movements. When the glands don’t empty properly, that fishy smell becomes constant and hard to ignore.
While anal glands are the top culprit regardless of sex, other causes range from mild infections to serious conditions. Here’s how to figure out what’s going on and what to do about it.
Anal Gland Problems: The Most Common Cause
Healthy anal glands release tiny amounts of fluid each time your dog poops. The pressure of a firm stool passing by does the work. But when the fluid thickens or the glands don’t empty fully, the sacs become impacted. They swell, grow uncomfortable, and leak that unmistakable fishy smell onto your dog’s fur, bedding, and furniture.
Impaction is the mildest stage of anal gland trouble, but it can progress. Bacteria can invade the overfull sac, causing infection (sacculitis). Left untreated, an abscess can form and eventually rupture through the skin near the anus, releasing blood and pus. Watch for these signs that your dog’s anal glands need attention:
- Scooting: dragging the rear end across the floor or grass
- Licking or biting: repeatedly targeting the area around the anus or base of the tail
- Visible swelling or redness beside the anus, sometimes with bloody discharge
- Tail held low, reluctance to sit, or straining during bowel movements
If your dog is scooting and the area smells strongly of fish, impacted anal glands are almost certainly the answer.
Breeds at Higher Risk
Research from the Royal Veterinary College found that certain breeds are significantly more prone to anal gland disorders. Cavalier King Charles Spaniels and King Charles Spaniels had more than three times the risk compared to mixed breeds. Cockapoos had about 2.5 times the risk, while Shih Tzus, Bichon Frises, and Cocker Spaniels also showed elevated rates. Flat-faced breeds in general had 2.6 times the risk compared to longer-snouted dogs, and spaniel types as a group had about twice the risk. Larger breeds like Boxers, German Shepherds, and Labrador Retrievers were at lower risk.
Causes Specific to Female Dogs
If you have a female dog and the smell seems to come from the vulva rather than the anus (they’re close together, so it can be hard to tell), a vaginal infection could be responsible. Vaginitis causes a sticky discharge that ranges from clear to cloudy. Puppies sometimes develop it before their first heat cycle, often with mild licking and small amounts of discharge but no other symptoms. Adult dogs can get it too, and symptoms tend to be more noticeable.
A far more serious possibility in unspayed females is pyometra, a bacterial infection of the uterus. In its “open” form, you’ll see a mucopurulent or bloody vaginal discharge that can smell foul. Pyometra is life-threatening. It can escalate into sepsis and organ failure without surgical treatment. If your unspayed female dog has a foul-smelling discharge along with lethargy, loss of appetite, increased thirst, or a swollen abdomen, this needs emergency veterinary care.
Causes Specific to Male Dogs
Male dogs normally produce a small amount of yellowish-green discharge from the prepuce (the sheath covering the penis). This is prostatic fluid, and a thin layer of it at the tip is not a problem. What you’re looking for is a change: thicker discharge, a stronger smell, or excessive licking at the prepuce.
Balanoposthitis, an inflammation of the prepuce and penis caused by bacteria, is extremely common. Nearly every male dog experiences it at some point, often around puberty. Most cases are mild and produce a small amount of purulent discharge without any other symptoms. In chronic cases, though, abscesses can form inside the prepuce, causing noticeable swelling and a stronger odor. If the discharge becomes bloody, heavy, or your dog can’t stop licking, it’s worth a vet visit.
Yeast Overgrowth in Skin Folds
A musty, “yeasty” smell coming from the groin, skin folds around the vulva, or the perianal area points to a different organism entirely. A type of yeast that naturally lives on dog skin can overgrow when conditions are warm, moist, or when the immune system is compromised. The groin and perivulvar skin are prime locations because they stay warm and don’t get much airflow.
The hallmark of yeast dermatitis is intense itching combined with an unpleasant odor that’s more sour or musty than fishy. You may also notice reddened, greasy, or thickened skin in the affected area. Dogs with allergies, hormonal imbalances, or those on long-term antibiotics are more susceptible. A vet can confirm yeast overgrowth with a simple skin swab.
Urinary Tract Infections
Foul-smelling urine is one of the most common signs of a urinary tract infection in dogs. If the fishy odor seems strongest when your dog urinates or you notice it on bedding where your dog has been lying, a UTI could be the source. Other signs include frequent urination, straining, accidents in the house, or blood-tinged urine. UTIs are more common in female dogs due to their shorter urinary tract, but males can develop them too.
How Anal Glands Are Treated
For simple impaction, a veterinarian or trained groomer can manually express the glands. This takes seconds and provides immediate relief. How often your dog needs this varies widely. Some dogs never need it; others need it every few weeks. The best approach is to watch for signs like scooting or licking and schedule an expression when symptoms return.
If your dog needs expression so frequently that it becomes burdensome, or if infections keep recurring, surgical removal of the anal sacs is an option. It’s a permanent fix, and most dogs recover without complications.
Preventing Anal Gland Problems
Firm stools are your best tool for keeping anal glands healthy. When stool is soft or loose, it doesn’t create enough pressure against the glands during a bowel movement, and the fluid stays trapped. Adding dietary fiber can make a real difference. Common options include psyllium husk, canned pumpkin (plain, not pie filling), or cellulose-based supplements. One study on dogs with large bowel issues found that a median dose of about 2 tablespoons of psyllium per day improved stool consistency, though individual dogs responded to anywhere from a quarter tablespoon to 6 tablespoons daily depending on size and condition.
Maintaining a healthy weight also matters. Overweight dogs tend to have weaker muscle tone around the anal area, which makes natural gland emptying less effective. Regular exercise and a balanced diet support both stool quality and the muscle function needed to keep those glands draining on their own.
How to Pinpoint the Source
Because the anus, vulva (or prepuce), and urinary opening are all in close proximity, it can be genuinely difficult to tell where the smell is coming from. A few practical steps can help you narrow it down. Lift your dog’s tail and look for swelling, redness, or discharge near the anus. Check the vulva or prepuce for unusual discharge. Note whether the smell gets worse after your dog poops (suggesting anal glands), after urination (suggesting a UTI), or is constant regardless of activity (suggesting infection or yeast). Pay attention to behavioral clues too: scooting points to anal glands, frequent licking of the vulva or prepuce suggests a localized infection, and straining to urinate points toward the urinary tract.
If the smell appeared suddenly, is getting worse, or comes with discharge, swelling, lethargy, or changes in appetite, your dog needs a veterinary exam to rule out infection or more serious conditions like pyometra.