Hypersalivation in Horses

Last Updated on February 25, 2022 by Allison Price

Does your horse drool like a dog? These are the reasons, from the benign to life-threatening.

Slobber, whether it comes from a dog or a horse, is gross. It’s also sexy, slimy and warm. While a dog’s drivel may be enough to send you to the bathroom, horses should be more alarming. Although excessive equine salivation may not be common, it is a sign of serious conditions that could have potentially life-threatening consequences for horses and their owners.

It is essential to begin with the normal in order to understand the abnormal. This includes understanding how horses produce saliva and how much they generate. There are three types of salivary glands in horses: the mandibular, sublingual and parotid. These glands produce almost 40 liters (10 gallons) of saliva every day. The saliva helps to moisten and lubricate food, allowing it to be transferred from the mouth to the stomach. Although saliva is mostly water, it also contains sodium and chloride, as well as sodium bicarbonate and enzyme amylase.

Hypersalivation in Horses

Equestrians may lust after the perfect pair of boots or the barn of their dreams. However, there are only a few reasons horses drool too much, according to Inge Wijnberg DVM, PhD Specialist Equine Internal Medicine KNMvD Dipl. ECEIM, taken from Utrecht University’s Department of Equine Sciences.

She says that there are only two main causes of excessive salivation in horses. They are increased saliva production or decreased salivation.

We will discuss several causes of hypersalivation in this article. Owners should consult their veterinarians immediately to address the problem.

Infectious Causes

It is best to start with the most frightening one, and move on. Rabies can be found in any animal. Horses are most often infected when infected animals bite them. The virus’ natural reservoirs are terrestrial carnivores (e.g., foxes, raccoons and skunks).

Infected animals can bite each other to spread the virus. The virus then multiplies at the site of the bite and invades sensory neurons, which are nerve cells that transmit information to the central nervous systems. The virus can enter the neurons through the long arms and nerve cells called axons. It is not detected by the immune system, so it is protected from any further infection. Infected horses often produce large amounts of saliva because the rabies virus prefers migration down peripheral nerves to their salivary glands.

Angela Pelzel McCluskey, DVM is an equine epidemiologist at USDA-APHIS Veterinary Services in Fort Collins, Colorado. “Rabies, one of the most fatal diseases in horses, is completely preventable with the appropriate vaccination,” she says. She adds that despite rabies vaccines being commercially available for horses since 1983, there was a recent study which reported 6,154 cases of rabies in 2010. This included 37 horses and donkeys.

Horse owners living in areas where rabies is endemic should consult their veterinarians to make sure their horses have been vaccinated. Owners who suspect their horses may have rabies should not allow their horses to come in contact with potentially deadly slobber.

Equine viral aeritis

Although reports of equine virus arteritis (EVA), outbreaks in the United States are rare, the virus responsible for it–equine arthritis virus (EAV–remains in domestic equine populations around the world.

EVA is a common sign in horses.

  • Fever;
  • Depression;
  • Edema (swelling below the abdomen) and limbs
  • Inflammation, erosions and vesicles (fluid filled sacs) in your mouth.
  • Hypersalivation.

Peter Timoney, MVB (MS, PhD), FRCVS of the Gluck Equine Resource Center at the University of Kentucky in Lexington, states that there has been an increase in EVA-related events over the past 20-30 years. This has been linked to increased international horse movement and trade in equine geneticplasm. EVA is only currently reported to animal health officials in a few states. There is no treatment and the industry suffers significant economic losses due to high abortion rates, young foals dying, and stallion carriers.

Borna virus

The potentially fatal Borna virus virus is similar to rabies in certain ways. It affects the horse’s nervous system and causes incoordination, behavior changes (somnolence or drowsiness), paralysis of the Pharynx, the area that extends from the rear end of the mouth and nasal passages, to the larynx or esophagus. This can lead to drooling.

Other Hypersalivation Causes

Heavy metal toxicityLead-contaminated pastures
Musculoskeletal disordersFractured bones in the mouth or hyoid device (voice box); temporohyoid Ostepathy (fusion of these bone, etc.
Infections or inflammation of the pharynxStrangles, Steptococcus Equi, Retropharyngeal Lymphadenopathy (pimples), swelling in the pharynx and guttural pouch Disease
Conditions of the oral cavityForeign pain, tongue injuries and inflammation, cellulitis, trauma, cellulitis, and other symptoms.
Primary salivary gland diseaseInflammation, salivary stones or mucocele formation (small, fluid-filled sacs), trauma, neoplasia (adenocarcinoma and melanoma),
Dysphagia (difficulty swallowing).Facial nerve trauma (pharyngeal paralysis), megaesophagus (esophageal mobility disorder),
Tongue abnormalityActinobacillus lignieresii infection (wooden tongue)

Toxic Causes


Horses can become hypersalivated from Rhizoctonia Leguminicola fungus that grows on clover, particularly red clover. The fungus produces two compounds: slaframine (or swainsonine), which can stimulate the parasympathetic nervous systems, leading to excessive saliva production.

“Hypersalivation” is a characteristic of Slaframine Toxicity. This is why the condition is sometimes called’slobbers. ‘” says Wijnberg. “Horses with slobbers were reported in various areas of the United States, including the central, southeast, and southwest U.S.”

Cows and ruminants can also be affected by slaframine poisoning. Other symptoms include anorexia and bloat, frequent urination and excessive eye tearing. However, excessive salivation, which is often the only sign that horses have ingested slaframine, is the most reliable indicator that they have been contaminated. Horses quickly recover from the toxicity once they have been eliminated. Although clover is not known to cause any damage, severe cases may result in photosensitization (increased skin susceptibility to UV light) or liver disease.

Organophosphate Toxicity

Certain types of phosphorus-containing insecticides designed to protect animals and plants can be toxic to horses. Organophosphates, which were historically used to treat parasitic infections such as pinworms and bots in horses, can cause serious poisoning in any animal if the toxic levels exceed what the body is capable of handling. Farmers using organophosphates can cause accidental agricultural poisonings.

The signs of initial toxicities are quite consistent among horses with toxicity. They include:

  • Excessive drooling;
  • Students with small learning needs
  • Frequent urination;
  • Diarrhea;
  • Colic; and
  • Difficulty in breathing.

Untreated horses can develop muscle spasms, nervousness, weakness, coordination problems, seizures, and nerve damage.


There are many types of ulcers that can develop on horses’ bodies, externally or internally. These include his tongue, stomach, stomach and right dorsalcolon. Horses with stomach, mouth, or esophagus ulcers are more likely to experience hypersalivation. The owners might notice signs such as difficulty eating, pain in the throat, colic, or anorexia in their horses.

Equine ulcers can be prevented and treated by owners.

  • It is important to use non-steroidal antiinflammatory drugs with caution, as they can cause kidney damage and ulcers.
  • Administering veterinarian-prescribed ranitidine or omeprazole to decrease acid production in the stomach; and
  • Use the protector sucralfate to cover the ulcer and let it heal.

Equine sickness

The mystery continues to plague horses across Europe, particularly in Scotland. However, veterinarians can diagnose the condition in other parts of the globe, including the United States. Although veterinarians aren’t sure what is causing this dysfunction in the autonomic nervous systems, one theory is that it is caused by a Clostridium bacterium toxin found in pastured horses. The toxin spreads throughout your body and causes classic symptoms such as colic, loss appetite, excessive salivation, and even death.

Causes of Gastrointestinal Disease

Oral or dental disease

During the 2013 American Association of Equine Practitioners (AAEP) Focus on Dentistry Abnormalities Jon Gieche, DVM and FAVD EQ of Kettle Moraine Equine Hospital, Whitewater, Wisconsin highlighted the importance of conducting oral examinations every six to twelve months starting at a foal’s newborn exam. Veterinarians can easily identify hypersalivation-inducing oral cavity abnormalities during a properly conducted oral examination, including:

  • Plaque;
  • Calculus (tartar);
  • Sulcular bleeding (between the gums and the tooth);
  • Gingivitis (gum inflammation);
  • Tooth mobility
  • Oral masses
  • Periodontal pockets are widened spaces between teeth that can lead to food getting stuck.
  • Malocclusion (a misaligned bite).

Gieche states that the most common causes of hypersalivation in the oral cavity are malocclusions, periodontal disease, trauma to dental soft tissue, dental hard tissue or supporting bone, foreign bodies, and oral masses/tumors. Hypersalivation can be caused by anything that can irritate or cause pain in the mouth.

Horses who choke have material in their esophagus which cannot pass to their stomachs as normal (hence, it is also called esophageal block). Choke symptoms include anxiety and extended neck. Gagging and retching may occur, especially if the obstruction is in the proximal or upper esophagus near the throat. A frothy, saliva-rich nasal discharge may be present. Hypersalivation and other signs can vary depending on the severity of the choke or the location of foreign material in the esophagus.

Gastroscopic neoplasia (tumors).

Researchers found that squamous cell carcinoma was the most common form of equine stomach cancer, despite it being rare. The most common symptoms in 24 horses with gastric cancer were inappetence and weight loss, colic, fever, and lethargy. They also observed hypersalivation (29%) in seven horses with gastric cancer.

Hepatic causes

Although rare in horses, liver diseases can be caused by ingesting grass products in pasture. Horses can get liver disease from ingesting compounds like pyrrolizidine alkaloid, which is common in some plants. Horses don’t like plants that contain PAs. However, horses may eat PA-containing plants during droughts or if they are accidentally bailed into hay.

Johanna R. Elfenbein DVM, Dipl., said that the liver controls energy metabolism and biotransforms or eliminates foreign substances. During her presentation at the 2011 AAEP Annual Convention, ACVIM was displayed. “Clinical signs of liver dysfunction can be non-specific and are usually caused by abnormalities in metabolism and excretion.”

Horses with hepatic dysfunction may experience icterus (jaundice), poor health, anorexia and lethargy, mild encephalopathy, and cerebral dysfunction. This can include behavior changes, stupors, comas, diarrhea, edemas, pruritus, excessive drinking, and hypersalivation.

Take-Home Message

Although there are many possible causes for hypersalivation, most sources agree that horses have a low incidence of increased saliva production. Horse owners should approach any slobbery horse with caution, especially because of the possibility of spreading rabies, which is a fatal disease that can be transmitted zoonotically. If in doubt, contact your veterinarian to inquire about your horse’s clinical symptoms.

Allison Price
Allison Price

I’m Allison, born and raised in San Diego California, the earliest memory I have with horses was at my grandfather’s farm. I used to sit at the stable as a kid and hang out with my Papa while he was training the horses. When I was invited to watch a horse riding competition, I got so fascinated with riding!