What Does It Mean When a Dog Smells Like Fish? | Anal Glands

A dog that starts smelling like fish often catches owners off guard. You’ve just given your dog a bath, yet the odor lingers or returns within hours. It’s easy to blame something they rolled in or their food, but the truth is usually simpler — and more specific.

A persistent fishy odor in dogs typically points to an issue with the anal glands, two small scent sacs near the rectum. When these glands become full, impacted, or infected, they release a strong fishy fluid. While this is the most common cause, dental disease, skin infections, or urinary tract problems can also produce a fishy smell. Understanding the source is the first step toward fixing it.

Understanding the Fishy Odor

Anal glands, also called anal sacs, are two small pouches located on either side of a dog’s anus. They produce a foul-smelling, fishy fluid used for scent marking. Normally, these sacs empty during bowel movements as stool passes, but sometimes they don’t empty fully.

When that happens, the fluid builds up and can leak onto the dog’s fur, bedding, or furniture, creating the fishy odor. The smell is distinctive because the fluid is designed to be potent — it’s meant to communicate with other dogs, not to be pleasant for human noses.

Dental disease is another common cause, but the odor source is usually the mouth rather than the rear. Bacteria building up on teeth and gums can produce a fishy or foul breath. Skin infections — especially in dogs with skin folds — and urinary tract infections can also contribute, though these are less frequent.

Why the Anal Glands Are Usually the Culprit

The fishy odor from anal glands is so noticeable that owners often describe it as unmistakable. When the glands are full or infected, the smell tends to be strong and persistent, and it often comes with behavioral clues.

• Location of the smell: The odor usually originates from the dog’s rear end and transfers to bedding or furniture. If the smell is strongest near the tail, anal glands are the likely cause.
• Scooting: Dogs drag their rear on the ground to try to relieve pressure or discomfort from full glands. This is often the first visible sign.
• Excessive licking: Dogs may lick their rear persistently. This can transfer the smell to their mouth, making their breath fishy too.
• Tail chasing or biting: Some dogs obsessively chase or bite at their tail due to irritation near the anus.
• Swelling or redness: If the area around the anus appears red or swollen, an infection or abscess may have developed.

If your dog shows one or more of these signs, a veterinarian can check the anal glands and express them if needed. Home expression is not recommended unless you’ve been trained, as improper technique can cause pain or damage.

Other Possible Causes of a Fishy Smell

Dental disease is another frequent reason for a fishy smell, particularly when it comes from the breath. According to some estimates, up to 80% of dogs have some form of dental disease by age three. Bacteria buildup on teeth and gums can produce a fishy or foul odor. If the smell seems to come from your dog’s mouth rather than its rear, a veterinary dental exam is the next step. The American Kennel Club discusses this alongside anal gland issues in its guide on fishy odor from anal glands.

Skin infections — yeast or bacterial — can also produce a fishy or musty smell, especially in dogs with skin folds, allergies, or underlying conditions. The odor may be general rather than localized to one area. Urinary tract infections are another possible source, often accompanied by frequent urination, accidents in the house, or an ammonia-like scent mixed with fishiness.

A less common cause is a diet high in fish oils or omega-3 supplements. While these are generally beneficial for skin and coat health, they can cause a mild fishy breath or skin odor in some dogs. This is usually harmless but worth noting if you’ve recently changed food.

Use this table as a quick reference to narrow down the likely cause. Keep in mind that some dogs may have more than one issue contributing to the smell.

What to Do About the Smell

Once you’ve identified the most probable source, you can take the right steps. Here are practical actions to address a fishy-smelling dog:

1. Check the location: Is the smell coming from the rear or the mouth? That narrows down the likely cause significantly.
2. Inspect the anal area: Look for redness, swelling, or discharge. Do not attempt to express the glands at home unless a vet has shown you how.
3. Schedule a vet visit: A veterinarian can express the glands if they’re full, prescribe antibiotics or anti-inflammatories for infection, or recommend a dental cleaning.
4. Improve dental hygiene: Daily brushing with dog-safe toothpaste, dental chews approved by the Veterinary Oral Health Council, and regular professional cleanings can prevent dental disease.
5. Rule out other causes: If no rear or dental signs are obvious, your vet may recommend bloodwork, urinalysis, or skin tests to check for UTIs or skin infections.

Bathing your dog may temporarily mask the odor, but it won’t fix the underlying issue. For anal gland problems, the smell will return once the fur dries because the fluid continues to leak.

When to See a Veterinarian

A fishy odor alone is not an emergency, but it does warrant a veterinary visit, especially if it persists. However, certain signs require more urgent attention. For example, if the area around the anus is red, swollen, and painful, or if you notice blood or pus, an abscess may have formed. PetMD’s guide on anal glands location and function describes how an infected gland can become a serious problem if left untreated.

If your dog also seems lethargic, loses appetite, or has a fever, these could indicate a systemic infection spreading from the anal glands or elsewhere. In such cases, contact your veterinarian promptly.

For dental causes, a fishy smell that doesn’t resolve with routine brushing may signal periodontal disease that requires professional scaling under anesthesia. Skin infections causing odor usually need medicated shampoos or antibiotics from your vet.

The Bottom Line

A fishy odor on your dog most often traces back to full or infected anal glands, but dental disease, skin infections, and UTIs are also possible. Look for accompanying signs like scooting, licking, or bad breath to narrow it down. A veterinary exam can pinpoint the cause and provide treatment.

If your dog is a small breed prone to anal gland issues, such as a Cocker Spaniel or Chihuahua, your veterinarian may recommend regular gland expression every 4 to 6 weeks as a preventative measure. Ignoring the smell rarely resolves it — a quick checkup usually brings relief for both you and your dog.