Halitosis in Dogs: Why Does My Pet Have Bad Breath?

Introduction

Halitosis, or bad breath, is a common problem in dogs. Normal dog breath should be fairly neutral, and not have an offensive smell. Just as in people, if pets have recently eaten, their breath will smell like their last meal, which would have been dog food—a smell which most people don’t find particularly pleasant.

Therefore, while much of the time a normal pet’s breath is not going to smell appealing to the human nose, it should not smell bad, or like something rotten.

When a pet has halitosis, the smell is often described as a sour milk smell. This odor often accompanies periodontal disease, and may result from bacteria that is associated with plaque, calculus, retained food particles, and unhealthy gum tissue in the mouth.

Periodontal disease is one of the most common diseases seen in veterinary medicine, affecting up to 90% of dogs by the time they are 3 years of age. First, bacteria forms an invisible film on the teeth (plaque), which then mineralizes into tartar, or calculus. This is irritating to the gums, causing gingivitis, which then develop pockets alongside the teeth, which trap more bacteria, and a vicious cycle begins.

By far, the most common cause of halitosis in pets is periodontal disease. Once it becomes established, the odor becomes stronger and more noticeable. Bad breath in pets is not caused by lung air odor or stomach smells, unless the pet has recently vomited.

How halitosis develops

• A bacterial film (pellicle) starts forming on your pet’s teeth within hours after cleaning.
• Bacteria attach to this pellicle within 6-8 hours, and plaque starts to form.
• In a few days, the plaque turns into calculus (mineralized plaque). 
• As calculus develops, gingival inflammation may occur (gingivitis) and progress into periodontitis (tooth support loss).  
• Eventually the bacteria change from mostly non-motile (lacking the ability to “swim” through fluid), gram-positive aerobic bacteria (requiring oxygen), to motile (having hairlike cilia and flagella, which allow them to “swim” through fluid), gram-negative anaerobic bacteria (require a no-oxygen environment). In other words, over time, the bacteria type changes to ones that can move around and don’t need oxygen.
• To simplify, as periodontal disease progresses, the type of bacteria living on your pet’s teeth and gums change. They go from being the sort that can’t move around (non-motile) and need oxygen to survive (gram-positive, aerobic), to ones that can move around (motile) and don’t need oxygen (gram-negative, anaerobic). The bacteria populations change to survive in this new environment.
• These Gram-negative bacteria include Porphyromonas, Bacteroides, Fusobacterium, and Actinomyces spp.
• The cycle of pellicle and calculus-building continues, with the gingiva becoming more inflamed over time. 
• The gingival sulcus (the space between a tooth and surrounding gingival tissue ) widens and deepens, and becomes a periodontal pocket which traps food and bacteria and their breakdown products, generating halitosis.
• The primary cause of halitosis is volatile sulfur compounds (VSCs) that are made by gram-negative anaerobic bacteria, which include hydrogen sulfide, methyl mercaptan, dimethyl sulfide, and volatile fatty acids. 
• The powerful smell of rotten eggs is caused by hydrogen sulfide, and the stink of feedlots is from methyl mercaptan. These smelly compounds might also contribute to gum disease. 

Small breed dogs are more prone to periodontal disease and halitosis. Genetic factors and retained deciduous teeth also contribute to this problem. You can read more about Retained Deciduous Teeth in our PHH article here.

As small breed dogs have small mouths but have the same number of teeth as in bigger dogs, their teeth are often crowded, twisted and maligned, so food, hair and other material gets trapped between them. Small breed dogs in particular require daily tooth brushing for optimal dental health. 

Other causes of bad breath, or of foul odor around the face or head of your pet, could include: 

• Lip fold pyoderma—a painful skin infection of the lips.
• Nasal fold pyoderma—moist, inflamed nasal folds, occurring in brachycephalic (flat-faced) dogs (such as Pugs).

• Foreign bodies—such as sticks or chews stuck between teeth or across the palate.
• Oral disease—periodontal disease, oral ulcers, inflammation of the tonsils or pharynx, or cancer of the oral cavity.
• Eating smelly food, rotten food, or coprophagy (eating feces).
• Metabolic diseases such as diabetes or kidney disease.
• Respiratory disease including inflammation or cancer of the sinuses and nose.
• Gastrointestinal disease including megaesophagus (enlarged, or distended esophagus with reduced ability to pass food to the stomach) and cancer.
• Trauma—fractures (more common in cats), injury from chewing electrical cords (especially in puppies), caustic agents (especially in dogs running loose).
• Infections of the mouth.
• Autoimmune disease of the oral cavity.

If your pet has halitosis, please see your veterinarian for a complete physical and oral examination. However, some sedation will be needed if your pet won’t allow a thorough oral exam while awake. You can always ask your veterinarian about combining procedures if there is time in their schedule, especially if your pet needs another procedure and needs to have sedation for their oral examination.  Please remember that your veterinarian will be doing their best to help your pet, and they may be very nervous about having someone examining their mouth.  Try to be as reassuring as possible for your pet’s sake, just like you would be for a child. 

As previously mentioned, the most common cause of halitosis is periodontal disease.  Once your veterinarian has ruled out other causes of halitosis in their examination, they will probably do blood work on your pet, and if your pet’s health allows, the doctor will recommend a thorough examination of the teeth and oral cavity under anesthesia, in addition to dental radiographs (X-rays). If this proves to be the case with your pet, when they are under anesthesia, the veterinary technician or veterinarian will perform intraoral radiography, measure pocket depths, assess tooth mobility, and chart your pet’s teeth.

Halitosis Treatment

After your veterinarian has reached a diagnosis for your pet’s bad breath, they can establish the treatment plan. Usually this consists of periodontal treatment, often requiring tooth extractions, and ongoing home care, with a schedule for repeat dental cleanings.

Your veterinary team will clean and polish your pet’s teeth, including subgingival scaling (cleaning below the gum line). Your veterinarian will use intraoral radiographs, oral assessment, and probing to determine which teeth, if any, are recommended to be extracted. Teeth with advanced periodontal disease (with greater than 50% loss of support), or loose teeth, will likely be extracted, with your permission (be sure to give it in advance). Absorbable sutures will be placed in most extraction sites. Appropriate pain control medication will be administered and also dispensed.

After your pet’s dental procedure, start oral home care immediately. If your pet had extractions, ask your veterinarian for an oral rinse you can use twice daily at home, starting the day after the dental cleaning. This can really help with healing. Start brushing with a soft toothbrush in two weeks, with a toothpaste your pet likes. Most pets love poultry flavored toothpaste, so try that flavor if your pet doesn’t have food sensitivities.

Most pets would do better after extractions if they had an oral rinse twice daily, yet veterinarians rarely send one home. This one has dilute chlorhexidine which is great. It also works well to help treat periodontal disease.

It can be intimidating to start a home care program for the first time, and we have some PHH articles to help you, but here are some brief notes. Starting with wipes is usually easier than going straight to a toothbrush for most pets. These finger wipes are textured so if you rub the tooth surfaces, you should get some effective cleaning done. They have some efficacy on their own, but will work better with a little enzymatic toothpaste such as Virbac CET enzymatic toothpaste.

Dogs usually love the flavor of this toothpaste.

This toothbrush kit has smaller brushes that can fit in a variety of dog mouths. You may want to start with the finger brush to teach your dog to open his mouth and touch their teeth, one at a time, using lots of treats. (Or try starting with wipes, as mentioned above.) Of course large dogs can have larger brushes. You may find the long-handled brushes available in pet stores and online are helpful and worth a try; I prefer shorter-handled brushes when available.

Many dogs love these tasty chews which can help keep their teeth a lot cleaner when used several times a week.

Another promising chew treat is this honeycomb shaped chew. It “flosses” the teeth as the dog chews and removes calculus.

Prescription medications are not usually used for halitosis as a stand-alone condition. When halitosis is secondary to periodontal disease, however, antibiotics may be part of the initial stages of treatment, especially with multiple tooth extractions. Good home care will help decrease gingival pocket depth, decreasing the environment for bacteria and physically removing them by cleaning. Controlling bacteria will help control odor, through decreasing the generation of VSCs.

Gels are available to apply weekly, and have been shown to delay the development of plaque in dogs. You can apply these with your finger, a cotton swab, or a rolled-up piece of gauze.

Oral care products with zinc can help inhibit halitosis. Zinc binds to the sulfur, inhibiting the odor. Note—this is only masking the odor, not treating the cause! (However, the VetOne ChloraZinc Rinse mentioned above also contains chlorhexidine, which is antibacterial, so it actually treats the cause of halitosis as well as inhibits the odor.)

Note—The Veterinary Oral Health Council (VOHC.org) authorizes the use of the VOHC Registered Seal on products intended to help retard plaque and tartar on the teeth of animals. If you purchase a product with their seal, it has been shown to be effective at removing plaque and tartar, but is not necessarily safe in other ways.

For example, treated rawhide has been shown to retard plaque and tartar, but as it can still be dangerous in terms of being a choking hazard, it must be given to dogs under strict supervision.

So if you notice that your pet has developed smelly breath, pay attention! Sometimes halitosis comes on so slowly that we don’t even realize that our pet’s breath would make a skunk faint, until dental disease is advanced. Check things out! Take your pet to the veterinarian and get them examined.

Get periodontal disease treated if present. Start a great home care protocol. Change that smelly breath to nice, normal, clean, neutral dog breath. Your friends and family will thank you for it, and when your four-legged best friend also thanks you for it with a big wet sloppy face kiss, you will be the MOST thankful for their clean doggy breath!