Fishy-smelling puppy breath usually comes from one of a handful of causes: something they ate, their anal glands, teething, or a buildup of bacteria in the mouth. Most of the time it’s harmless and temporary, but a persistent fishy smell can occasionally point to something worth checking out.
The Anal Gland Connection
This is the most common reason puppy breath smells specifically like fish, and it catches most new dog owners off guard. Dogs have two small sacs just inside the anus that produce a strong, oily, fishy-smelling fluid. When a puppy licks or grooms their rear end, that fluid transfers to their mouth and tongue, and the next time they pant in your face, you get a wave of it.
Puppies groom themselves frequently, so even normal, healthy anal glands can produce enough odor to make their breath noticeably fishy. But sometimes the glands become impacted, meaning the fluid doesn’t empty properly and builds up. Anal sac impaction affects roughly 9% of dogs overall, though veterinarians report it’s far more common in adults than in puppies. Signs that the glands are actually bothering your puppy include scooting their bottom across the floor, licking or biting at the base of their tail, and visible discomfort when sitting down. If you’re seeing those behaviors alongside the fishy breath, a vet can express the glands manually, which usually resolves the smell quickly.
Teething and Gum Changes
Puppies go through a full set of baby teeth before their adult teeth come in, and the process creates plenty of opportunity for odd smells. Baby teeth start erupting as early as 3 to 4 weeks old, and puppies begin losing them around 4 months. The adult teeth replace them on a rolling schedule: incisors arrive around 4 to 5 months, canines at 5 to 6 months, and the final molars don’t finish coming in until 6 to 7 months of age.
During this entire window, small amounts of blood from the gums mix with saliva and bacteria in the mouth. That combination can produce a metallic or fishy odor. You might also notice your puppy drooling more, chewing on everything, or having slightly pink-tinged saliva. This is all normal teething behavior, and the smell typically fades once the adult teeth are fully in place, usually by 7 months or so.
Occasionally a baby tooth doesn’t fall out on its own, and the adult tooth grows in beside it. These retained baby teeth create tight gaps where food and bacteria get trapped, which can make breath smell worse than normal teething would. If you notice what looks like a double row of teeth, that’s worth mentioning at your next vet visit, since the retained tooth usually needs to be pulled.
Diet and Scavenging
Puppies put everything in their mouths. If yours recently got into the trash, ate something dead in the yard, or sampled cat litter, the fishy smell could simply be the remnants of whatever they found. Fish-based dog foods and treats (salmon, whitefish, fish oil supplements) are also obvious culprits. The oils in these foods coat the mouth and linger.
Coprophagia, the habit of eating feces, is surprisingly common in puppies and produces breath that many owners describe as fishy or intensely foul. If you’ve ruled out other causes, watch whether your puppy is snacking on their own stool or another pet’s. Most puppies grow out of this, but picking up waste promptly and redirecting the behavior helps break the habit faster.
Bacterial Buildup in the Mouth
Even young puppies can develop bacterial overgrowth on their teeth and gums, especially if they eat wet food exclusively or chew on soft toys that harbor moisture. The bacteria produce sulfur compounds that smell fishy or rotten. This isn’t the same as full-blown periodontal disease, which takes months or years to develop, but it’s the early version of the same process.
Getting your puppy used to having their teeth brushed early makes a real difference. A soft finger brush with dog-safe toothpaste a few times a week removes the film of bacteria before it hardens into tarite. Starting young also means your dog tolerates tooth brushing as an adult, when dental disease becomes a much bigger concern. Dental chews designed for puppies can help too, though they work best as a supplement to brushing rather than a replacement.
When the Smell Signals Something More Serious
In rare cases, persistently foul breath in a puppy can indicate an underlying health problem. Kidney issues cause a distinct ammonia-like odor on the breath as toxins build up in the bloodstream. This is uncommon in puppies but not impossible, and it’s usually accompanied by other symptoms like increased thirst, frequent urination, lethargy, or vomiting.
Gastrointestinal problems, including intestinal parasites, can also contribute to bad breath. Puppies are especially prone to worms and other parasites in their first months of life, and a heavy parasite load can cause digestive issues that affect the way their breath smells. If the fishy odor is paired with diarrhea, bloating, weight loss, or a dull coat, parasites are a reasonable thing to rule out.
A foreign object stuck between the teeth or lodged in the gums can cause localized infection and a sudden change in breath smell. Puppies that chew sticks, bones, or hard toys sometimes get splinters wedged along the gum line. Check inside the mouth if the smell appeared suddenly and your puppy seems to be pawing at their face or reluctant to eat.
What Actually Helps
For most puppies, fishy breath is a phase. The combination of teething, anal gland grooming, and an indiscriminate appetite creates a perfect storm of unpleasant mouth odor that largely resolves on its own by the time adult teeth are fully in. In the meantime, a few practical steps make a noticeable difference:
- Brush their teeth early and often. Even two to three times a week with a puppy-safe toothpaste reduces bacterial buildup significantly.
- Provide appropriate chew toys. Chewing naturally scrapes bacteria off teeth and stimulates saliva production, which helps rinse the mouth.
- Check their diet. If you’re feeding fish-based food or giving fish oil, that alone could explain the smell. Switching proteins temporarily is an easy test.
- Watch for scooting. If your puppy is dragging their rear on the ground and licking excessively, the anal glands are the likely source and may need to be expressed.
- Look inside the mouth. Swollen gums, retained baby teeth, stuck objects, or unusual redness give you useful information before a vet visit.
Fishy puppy breath is one of those things that sounds alarming but is almost always benign. If the smell is mild, comes and goes, and your puppy is otherwise eating, drinking, and playing normally, you’re most likely just waiting out teething or catching the aftermath of a grooming session. A smell that’s intense, constant, or paired with behavioral changes is the version that warrants a closer look.