Why does my dog smell like fish?

It’s jarring when a dog you know well suddenly smells like fish. That scent can mean anything from a smelly swim to a problem that needs medical care. Understanding why the odor occurs helps you choose the right next step — a quick bath, a behavior fix, or a trip to the vet — and keeps your home, guests, and other dogs comfortable.

Why a fishy odor matters for your dog’s health — and your home

Dog lovers commonly notice a fishy smell in a few everyday situations: wandering into the house after a walk and the whole room smells; guests commenting when your dog climbs into their lap; or one dog in a multi-dog household repeatedly giving off an unpleasant odor. In rescue or shelter settings, a fishy odor can influence adoption impressions and may hint at untreated medical problems.

Deciding what to do next depends on context. A brief, outdoor exposure usually calls for cleaning; repeated or worsening smells may mean a skin or anal-sac condition that benefits from veterinary treatment. In homes with several dogs, identifying the source quickly prevents unnecessary stress and cross-contamination of skin issues or parasites.

The short take: most likely causes of a fishy smell

The most common reasons a dog smells like fish are issues around the rear, especially impacted or infected anal sacs, and skin infections that favor yeast overgrowth. Dogs that have rolled in dead fish or carrion, or that eat a fish-heavy diet, can also smell fishy without a medical problem. If the odor is short-lived and tied to an obvious event — a beach day, a carcass, or a new food — it’s often harmless and resolved with cleaning. Persistent, strong odors or smells accompanied by scooting, licking, redness, swelling, or changes in behavior are more concerning and should prompt a vet visit.

What’s behind the scent — glands, bacteria and normal dog chemistry

Dogs have small glands on either side of the anus called anal sacs that hold a dark, oily secretion. Those secretions normally have a musky, distinctive scent dogs use for chemical communication; they mark territory and identity when released. If a sac becomes blocked, inflamed, or infected, the material inside can become concentrated and develop a sharp, fishy or rancid smell that is often noticeable to people.

The skin itself hosts a community of microbes that can influence odor. Certain yeasts, especially Malassezia species, may overgrow on warm, damp skin folds or in allergic dogs and produce a yeasty, musty, sometimes fishy scent. Sebaceous glands make oils that bacteria and yeasts break down into odor-producing compounds; increased oil production, skin damage, or moisture can shift that balance and worsen smells.

Timing clues: when and where the smell typically appears

Timing gives clues. If the smell shows up after a visit to a shoreline, pond, or a walk where your dog rolled in something, the source is probably environmental. A wet, oily coat that hasn’t been dried thoroughly after swimming can also start to smell as microbes act on the skin’s oils.

When odors coincide with skin symptoms — redness, flaking, greasy hair, or a musty smell from ears — a yeast or bacterial skin infection is likely. Some dogs flare up during allergy seasons, which makes the skin more hospitable to microbial overgrowth and associated odors. If the smell follows a change in diet to a fish-based formula, the food can alter body odors and breath; that’s more common in dogs fed high amounts of fish oil or whole fish regularly.

Skipping routine grooming or leaving fur damp after baths increases the chance of persistent odors, because moisture allows microbes to proliferate and oils to break down.

Warning signs that the odor could indicate a serious issue

Not all fishy smells are emergencies, but certain signs suggest a medical problem. Around the rear, look for swelling, warmth, pain when touched, repeated scooting, or persistent licking — these may suggest impacted or infected anal sacs. Visible pus, blood, or a sudden, very strong odor often indicates infection.

Systemic signs like fever, appetite loss, lethargy, or sudden changes in temperament alongside odor point to a more serious condition that needs examination and likely antibiotics or other treatments. Rapid-onset, severe odor coupled with open skin lesions, hair loss, or a foul discharge is a strong signal to see a veterinarian promptly.

Right now: simple checks and immediate steps for owners

1. Locate the source first. Check the coat, around the anus, the ears, and the mouth. Smells that follow wetting or bathing often come from the skin or coat; a strong scent at the base of the tail or leaking material suggests an anal sac problem.
2. Clean the affected area gently with dog-safe products. A mild, vet-recommended shampoo or a dog wipe removes surface debris and can reduce odor temporarily. Dry thoroughly, because moisture often makes smells worse.
3. Avoid trying to manually express anal sacs unless you’ve been trained by a professional. Incorrect expression can cause trauma or push infected material into tissues. If you smell a strong, fecal or fishy odor from the sacs, call your vet to discuss professional expression or evaluation.
4. Document frequency and triggers. Note when the odor appears, what you did (walk location, bathing, diet change), and any other symptoms. These details help your veterinarian narrow down causes and recommend targeted treatment.
5. If you detect swelling, pain, pus, or if the dog shows systemic signs, arrange a veterinary visit rather than delaying. Early treatment of infected sacs or skin infections shortens recovery and prevents spread to other dogs.

Keeping it away: prevention and routine care to reduce odors

Prevention combines behavior, environment, grooming, and diet. Training reliable recall and a strong “leave it” reduces the odds your dog will roll in dead fish or other smelly things. During walks near water or fishing areas, keep dogs on a short leash and steer clear of obvious carcasses or fishing waste.

Remove attractants from your yard and pickup areas where fish remains or trash might accumulate. If you live near shorelines, rinse and dry your dog after swims and check the coat for debris. Maintain a regular grooming routine appropriate for your dog’s coat type — frequent brushing, scheduled baths with vet-approved shampoos when needed, and careful drying — because clean, dry skin is less hospitable to smelly microbes.

If diet seems related — for example, a new fish-heavy food coincides with a persistent odor — consider discussing alternatives with your veterinarian. Sometimes switching proteins or balancing oils reduces body- and breath-odors without sacrificing nutrition.

For dogs prone to yeast or bacterial skin issues, addressing underlying allergies or skin inflammation often reduces odor recurrence. Your veterinarian may recommend medicated shampoos, topical treatments, or prescription therapy when over-the-counter products don’t do the job.

Grooming tools and products vets actually recommend

• Dog-formulated enzymatic odor removers and spot cleaners: these break down organic material and reduce lingering smells; pick products labeled safe for canine skin.
• Medicated or antifungal shampoos prescribed by your vet for recurrent yeast or bacterial problems; use as directed and dry the coat thoroughly with high-absorbency towels or a low-heat dryer setting.
• Disposable gloves, pet wipes for quick cleanups, and odor-neutralizing sprays designed for pets (avoid human deodorants or essential oils that can harm dogs).
• Professional grooming tools and anal-gland kits: these are best left to trained groomers or veterinarians. If a groomer or vet recommends a home tool, ask for a demonstration and clear instructions first.

If the smell persists: when to escalate and what diagnostics to expect

If cleaning and simple fixes don’t clear the odor within a few days, or if it returns frequently despite preventive steps, a veterinary evaluation is warranted. A vet will examine the skin and anal sacs, possibly take cytology (skin or sac smears) to look for yeast or bacteria, and may recommend culture, antibiotics, anti-yeast treatments, or anti-inflammatory therapy depending on findings.

For chronic anal sac problems, some dogs benefit from routine professional expression or, in recurrent severe cases, surgical discussion. For chronic skin yeast or bacterial infections, identifying and managing underlying causes — allergies, endocrine disease, or moisture-prone conformation — is the long-term solution. I typically see the best outcomes when owners track triggers closely and share that history with their veterinarian.

When in doubt, err on the side of a veterinary visit rather than prolonged home treatment, because persistent infections can be painful and harder to resolve the longer they’re left untreated.

Selected sources and further reading

• Merck Veterinary Manual: “Anal Sac Disease in Dogs” — Merck & Co., Inc.
• American Veterinary Medical Association (AVMA): “Anal Gland Problems in Dogs and Cats” resource page
• American College of Veterinary Dermatology (ACVD): Client information on yeast dermatitis and skin infections
• Journal of Small Animal Practice: review articles on anal sac disease and management in dogs (search for “anal sac disease review J Small Anim Pract”)
• Veterinary Dermatology: reviews on Malassezia pachydermatis and its role in canine skin and ear disease