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What is Saliva and How is It Produced? 

 

In order to understand abnormal causes of excessive drooling in dogs, it is important to consider the normal composition and physiology of saliva.

Saliva is constantly produced and secreted into the oral cavity from a dog’s salivary glands. Dogs have four pairs of major salivary glands and several other minor ones that drain within the oral cavity. The major salivary glands in the dog include the parotid, mandibular, sublingual and zygomatic salivary glands.

Saliva is a multifunctional fluid that lubricates food and facilitates the transportation of a food bolus through the esophagus. Other functions of saliva include keeping the mouth moist, thermoregulation (through evaporative cooling), oral cavity cleansing, reduction of oral bacterial growth, and protection of the tissues in the oral cavity.

Saliva is largely made of water, but it also contains enzymes that start the digestion of carbohydrates, mucus, and salts. The production of saliva is regulated by the body’s autonomic nervous system.

Some dogs produce more saliva than others. Certain giant breed dogs that are known for drooling include Saint Bernards, Mastiffs, and Newfoundlands. These breeds don’t necessarily produce excessive saliva, but their loose lip folds do a poor job of confining their saliva within their oral cavity. Brachycephalic breeds, or dogs with flatter faces like Bulldogs, tend to drool more as well because their faces contain skin flaps that trap saliva.

 

When is Drooling Considered Excessive in Dogs? 

 

Excessive drooling in dogs is divided into two categories: excessive saliva production (ptyalism) or the inability to swallow normal saliva production (pseudoptyalism). Chronic (long-standing) ptyalism is most commonly caused by a reluctance or inability to swallow rather than increased salivary flow or production.

Physiologic causes of increased saliva production in dogs include hyperthermia (overheating), excitement, and in response to feeding. Heat and excitement have an acute (quick) onset without other obvious signs of illness.

Pathological reasons for excessive drooling in your companion may include a diverse array of underlying medical conditions. 

 

Understanding the Cause of Your Pooch’s Excessive Drooling

 

In order to differentiate between the many potential causes of drooling, a complete medical history and physical examination are both required by a veterinary medical team.

A full oral examination should be performed by a veterinarian. They will look for signs of oral pathology including periodontal disease, stomatitis, immune-mediated disease, tongue lesions, oropharyngeal disease, and/or lip fold abnormalities. Acute exposure of the internal contents of the tooth (ie. pulp tissue), ulceration of the tissue inside of the oral cavity, and foreign bodies are common oral causes.

For better or worse, dogs love to put foreign objects in their mouths. Unfortunately, this can lead to small and sometimes even large foreign material becoming trapped in between the teeth or throat region. Wood chips, pieces of plastic, bone fragments (from chewing on bones), and string are frequent hazards.

Clinical signs that you may notice in your pet that indicate orofacial discomfort include pawing at their face or mouth and/or changes in eating behavior. Any changes to the color of saliva should also be noted. Blood-tinged or yellow (purulent) saliva can also be suggestive of a primary oral problem. 

 

What if the Oral Exam is Inconclusive? 

 

If the oral cavity shows no evidence of an underlying cause for excessive drooling, then other body systems need to be considered. These include the neurologic system, gastrointestinal system, and the salivary glands.

Blood work and advanced imaging may be recommended if the excessive drooling is suspected to be secondary to pathology (disease) of one of these organ systems. 

 

Salavary Glands

The overall incidence of salivary gland disease in dogs has been reported to be quite low (less than 1%). Tumors of the salivary gland tissue account for around 30% of this overall low rate.

Sialadenitis, or inflammation of one or more salivary glands, accounts for about a quarter of the overall incidence rate of salivary disease, both as a primary and secondary disease. Sialadenitis often presents as an obvious enlargement of the salivary gland tissue noticeable by the veterinarian and/or the pet owner.

The enlarged salivary gland often represents the formation of a salivary mucocele (or sialocele). Salivary mucoceles are accumulations of saliva in the soft tissue surrounding the glands that may make up to 9% of all salivary gland disease. Possible causes of a salivary mucocele include injury, infection, or immune-mediated disease.

Sialadenosis is a non-inflammatory swelling of the salivary glands, most commonly affecting the mandibular salivary glands. The cause of this disease is unknown. Affected glands are enlarged but are usually non-painful.

Ptyalism has been documented in cases with congenitally (present at birth) enlarged salivary ducts, but these are rare primary salivary gland abnormalities and can be managed well with surgery by either a board-certified veterinary dentist or a board-certified veterinary surgeon.

 

Gastrointestinal System

Gastrointestinal disease can often be the cause of nausea, which can in turn lead to ptyalism in both dogs and people alike. Esophageal and gastric (stomach) disorders can be causes of excessive drooling. Severely sick dogs with advanced renal (kidney) or liver dysfunction often have ptyalism, but this sign is typically accompanied by other signs of systemic illness. Halitosis (bad breath) may be indicative of oral, esophageal, or gastric disease.

 

Neurologic System

Examples of abnormalities of the nervous system that cause excessive drooling are seizures, infectious diseases (Rabies virus, etc.), and dysfunction of the major nerves that exit directly from the brain (cranial nerves).

When evaluating patients with ptyalism or pseudoptyalism, relevant medical history includes recent exposure to toxins, medications, and/or topical human and veterinary skin products. These substances can be bitter or damaging to the oral tissues.

Examples of toxic substances include household cleaners, plants/trees (eg, Kentucky coffee tree, poinsettia), insecticide/pesticide (eg, boric acid, aldicarb), rodenticide (eg, zinc phosphide), human sleep aids (eg, zolpidem), mushrooms (eg, Amanita muscaria), Metaldehyde, human tricyclic antidepressants (eg, clozapine), and 5-hydroxytryptophan (ie, Griffonia seed extract).

Envenomization from spiders, scorpions, toads, or coral snakes can also cause excessive drooling.

 

Other Considerations

It is also important to consider any known trauma to the oral cavity including electrical cord injury.

History of vaccination is extremely important. As mentioned previously, viruses, most importantly Rabies virus, can be both a veterinary and human health concern for obvious reasons. This is a life-threatening disease and the proper health authorities need to be notified immediately if any animal (or human) is suspect to have Rabies. Other infectious causes can be systemic bacterial infections such as leptospirosis.

Young dogs are typically more likely to ingest toxins and/or foreign objects, but adult dogs are susceptible to this as well. The duration of ptyalism is important because in some patients this helps differentiate between oral trauma and cancer.

 

Treating Excessive Drooling in Dogs

 

Treatment for excessive drooling depends on the underlying cause. If there is toxin exposure, then decontamination (oftentimes with activated charcoal), supportive care (with hospitalization and/or fluid therapy), or a specific antidote (if available) are recommended.

If an underlying oral cause is identified, then a COHAT (Comprehensive Oral Health Assessment and Treatment) under anesthesia is indicated followed by imaging of the oral tissues. For primary salivary gland diseases and/or dental disease, surgical intervention is typically warranted for the treatment of excessive drooling.

 

Veterinary Dentist in Colorado Springs

 

Early diagnosis and treatment of ptyalism and pseudoptyalism can be very important. If you suspect that your dog may have this condition due to excessive drooling, please schedule an appointment with your primary care veterinarian or one of our board-certified veterinary dentists or residents at Animal Dental Care & Oral Surgery in Colorado Springs.

 

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