Why Do Horses Foam at The Mouth: The Many Triggers Behind Horse Mouth Foam (And How to Help)

Do you know what causes horses to foam at the mouth? Is it something you should be concerned about? When I am about to give a treat to my horse as an appreciation for its good activity, it always wants to have a carrot as a treat. 

When I show the carrot to my horse, it drools with excitement, indicating its delight for the treat. Humans react similarly when they see their favorite food. 

When we see tamarind or any kind of sour thing, what happens to us? Saliva comes out from the mouth. This is normal for both horses and humans. Just due to a special protein horse's saliva becomes foamy…this is the difference. 

But when this foamy saliva is considered abnormal or indicates any medical condition? Recently, it happened to my friend's horse. Foaming appears continuously at the mouth of his horse even in a resting condition. He became worried and called a veterinarian. The vet said that it's not a normal foamy saliva. It's a serious medical condition and needs treatment. 

There are a lot of facts about horse foam at the mouth. We need to identify them to distinguish normal and abnormal foamy saliva. So, what would be the causes of foam build-up in your horse's mouth?

Foaming at the Mouth of Horses: What does it really mean?

Foaming arises due to excessive saliva formation in the horse's mouth. This excessive saliva turns into a foamy substance due to the presence of a surfactant protein, called latherin. This protein is present in a high concentration in the horse's saliva and creates this foaminess.

Intensity level of foaminess

• Confined in the lips area
• Foam spreads throughout the mouth
• Spreads from the mouth area to the chest

What are the natural causes of foam buildup in a horse's mouth? 

Apart from various medical factors, a horse naturally experiences foam buildup in its mouth. This is a part of the normal physiological process of horses. So, what situations trigger the appearance of foam in your horse's mouth? 

Normal production of saliva with the influence of a special protein

This foamy saliva forms naturally in their mouth due to chewing and helps digest their food such as pasture grasses, hay, legumes, and other dry forages.

When working with bit and bridle

Sufficient foaminess is desired to lubricate or smooth the bit and bridle surface. It helps to reduce the abrasion of these tacks with the teeth and mouth area of the horse. However, excessive foaming in the mouth indicates a discomfort with the bit. If you use a sturdy bit, that does not fit properly to the horse's mouth, causing excessive pressure. Ultimately, it stimulates the production of saliva. 

Salivation during exercise

During physical activities like training and exercise, foam may develop at the mouth as a response to stress release. 

Explore more: 

Horse Riding Adventure: Dealing with a horse with dropped fetlocks.

What are the medical concerns that are related to foam around a horse's mouth?

A horse's mouth becomes frothy if the oral health of horses gets compromised due to various gastrointestinal, viral, and bacterial diseases. What are those health issues?

Oral ulcer, gum disease, tongue injury, and choke (Swallowing difficulty)

Irritation and discomfort in the Stomach, liver, oral cavity, tongue area, and difficulty in swallowing cause excessive production of saliva. Additionally, gastric neuritis (tumor in the stomach) and liver disease affect oral health, ultimately causing foamy saliva. 

Viral Infection: Rabies, Borna Disease and Arteritis 

When an infected animal bites the horses, they become infected with rabies. The genetic material of this virus enters the nerve cells of the brain. Then it migrates to the salivary gland and causes the formation of excessive foamy saliva. 

Just like the same way, Borna Disease Virus (BDV) affects the equine nerve cells and migrates to the esophagus and larynx (part of the digestive system). As a result, excessive drooling occurs. 

On the other hand, equine arterial virus is transmitted via infected semen of male horses and causes inflammation in the mouth. 

Exposure to heavy metal and poison

When the horses graze in the heavy metal-contaminated pasture, their immune system recognizes these harmful substances and increases saliva production to flush out the toxins. This is an outcome of the body's defense mechanism against the harmful particles. 

Bacterial Infection: Wooden Tongue and Grass Sickness

Wooden tongue occurs due to bacterial infections. The symptom of this disease starts from diarrhea, then inflammation occurs in the brain and spinal cord and spreads throughout the body. The tongue of the horse becomes hard and swollen due to the formation of abscesses. As a consequence, foamy saliva is secreted. 

On the other hand, grass sickness also occurs due to a bacterial infection in the grazing area of horses. 

What came to your mind when you heard the name, grass sickness? Probably a bacteria that resides in the grass causing the disease….yes you are right. Affected foal amr horses can not eat foods due to difficulty in swallowing, ultimately causing excessive drooling. 

How are some mental and behavioral factors linked to a horse’s foam at the mouth?

Different mental and behavioral issues like stress, fear, excitement, or relaxation can stimulate the production of saliva at the mouth. So, how are these factors linked to foamy saliva?

Stress-free moments: mindful relaxation 

The horse drools when it feels calm and happily checks out its surroundings. 

Stress and anxiety

Drooling also happens when they are stressed or anxious about something. 

Deep Emotions: fear or excitement 

Being in an unfamiliar environment with unknown horses and people makes them drool out of fear and excitement. 

How does a reaction to certain substances with saliva cause horses to foam at the mouth?

Substances from certain plants and some pain relieving medications react to the saliva and cause excessive foaminess.

Foaming due to ingestion of certain plants

Plants that contain sharp points on the seeds, cause tissue injury in the mouth of horses, and ultimately foamy saliva forms. A harmful fungus grows on certain wild plants such as red and white clover, causing excessive foamy drool formation in the mouth. 

Additionally, foxtail burley, raspberry canes, burdock, and other long-spined plants are also responsible for this foaminess. 

Response to medication or supplements

Excessive drooling is a potential side effect of certain pain-relieving medications. Methamphetamine is an opiate medication of that type, mostly used to reduce pain in horses after racing injury. 

How can you focus on the prevention and care to resolve this excessive foam accumulation?

You can manage this health concern by following some preventive measures and ensuring proper horse care.

Regular dental checkups

You must regularly check your horse's dental condition and maintain oral hygiene to protect the mouth area from any kind of infection. While checking if you find any injury or infection, immediately consult a veterinarian. 

Proper bit fitting and use

Make sure the bit fits correctly with the horse's mouth. Avoid harsh and sturdy bits to protect your horse's mouth area from any damage. Just remember: you have to use the bit accurately according to the riding requirements and your horse’s preference. If you are not doing any athletic riding activities, skip using a bit. 

Checking for signs of discomfort

Monitor the body parts of your horse for signs of discomfort or lesions. Seek help from a horse specialist, if you can not identify the causes of this foamy saliva.

To Sum Up

Foamy saliva in horses is a natural response to physiological stimuli. But it can also be associated with specific medical concerns and reactions to certain substances. 

In this concise discussion, we have tried to draw a clear picture about the reasons behind the horses' foam at the mouth. If you find this information useful, leave a comment below. And share it with others dealing with excessive drooling in their horses.