Why does my dog have bad breath?

Why bad breath is not a “normal dog thing”

A temporary smell after a meal, or after a dog has chewed something particular, is understandable and short-lived. Persistent halitosis that does not go away over days and weeks is another matter. In dogs, such a smell is in most cases linked to disease of the teeth, gums or periodontal tissues.

Some breeds — especially small ones — are prone to faster build-up of plaque because their teeth are crowded and there is less space between them. But that does not mean the smell is “given by nature”. It means such a dog needs more careful prevention and regular check-ups.

Dental plaque and tartar

It all begins with a soft film of bacterial plaque on the tooth surface. If it is not removed regularly, it mineralises and turns into hard tartar. Tartar creates a rough surface on which bacteria build up even faster.

It is the by-products of these bacteria that give the characteristic bad smell. It is important to understand that visible tartar on the crowns of the teeth is only the tip of the iceberg. Under the gums, tartar keeps irritating the tissues and sustaining inflammation.

• A yellowish-brown film near the gumline
• Hard deposits on the teeth that a toothbrush will not remove
• A smell that gets stronger even though the dog eats regularly

Gingivitis — inflammation of the gums

Gingivitis is inflammation of the gums without any marked loss of the tooth's bony support yet. The gums become red and swollen and bleed during meals or when in contact with toys. Inflamed tissues give off a smell that owners describe as “rotten” or “metallic”.

Plaque-induced gingivitis can be reversible once the bacterial plaque is removed and home care is good, provided there is no loss of periodontal attachment yet. If gingivitis is ignored, the inflammation spreads deeper — to periodontitis.

Periodontitis and periodontal pockets

Periodontitis involves loss of periodontal attachment, the formation of periodontal pockets and a reduction in the bony support of the tooth. Bacterial plaque and debris collect in the pockets, and with active inflammation purulent discharge may appear — and then the smell becomes especially persistent.

Periodontal disease can affect different groups of teeth. Its severity is assessed from periodontal probing and dental X-rays, not only from how the tooth looks. From the outside a tooth may look only slightly darkened, while under the gums there is already significant damage.

• Deepened periodontal pockets
• Loose teeth at the later stages
• Discharge from a pocket — an additional source of smell

Damaged, cracked and infected teeth

The smell can also come from one particular tooth: a cracked crown, a fracture, damage to the pulp, infection in the root canal or an abscess at the root. Such a tooth sometimes changes colour and sometimes does not. A dog may chew on one side or avoid hard toys, but does not always refuse food altogether.

That is why I insist on a full examination of every tooth under anaesthesia, with dental X-rays. A tooth that looks “intact” from outside can be a source of chronic pain and smell.

Why a puppy's breath may smell

While a puppy is changing its baby teeth, short-lived local tenderness of the gums or slight temporary changes in smell can occasionally appear. This does not mean that any smell during this period is “normal” and can be ignored.

Retained baby teeth can cause crowding and areas where plaque builds up more easily. Gingivitis, injury, a foreign object, a problem with the bite or a damaged tooth can also lead to a smell.

A persistent, strong, worsening or unusual smell should not be put off “for later”. If the smell comes with bleeding, swelling, excessive drooling, pain, reduced appetite, refusing hard food or avoiding having the face touched, a dental examination is needed.

• Short-lived mild changes while the teeth are being replaced are possible, but are not a universal explanation
• Retained baby teeth and crowding can sustain plaque build-up
• A persistent or worsening smell needs assessment, not waiting

Why a dog may keep eating even when it hurts

Dogs can keep eating despite dental pain, gradually changing how they pick up and chew their food. The owner notices only the smell — and concludes that “if he eats, everything is fine”.

At the appointment I look for subtle changes: the dog takes food but quickly walks away from the bowl; chews on one side; chooses soft food; pulls less on toys; rubs its face on the carpet. These details often appear before a dog refuses food.

When the smell may not be only dental

In the great majority of dogs I find the cause of halitosis in the mouth. However, an unusual smell can sometimes go with systemic disease — kidney failure, diabetes, some metabolic disorders. This is not the typical story, but a clinical assessment should always be made. How to tell such a smell apart is in the article on the smell of acetone, urine or fish from the mouth.

If the smell does not lessen after proper dental treatment, I recommend an additional general examination and laboratory tests. It is important not to assume a “stomach” cause blindly — without an examination of the mouth, that is only a guess.

What helps and what the plan is

Brushing your dog's teeth at home with veterinary toothpaste reduces plaque and slows the formation of tartar. But it does not replace oral cavity sanitation if tartar is already under the gums. Chews can be a supplement, but not a treatment for inflammation.

At the consultation I assess the condition of the mouth, plan a full COHAT examination with X-rays where needed, and draw up an individual plan: hygiene, periodontal treatment, extraction or preservation of teeth — depending on the diagnosis.

Frequently asked questions