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Why Does My Horse Drool? 10 Most Common Causes

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Recently, a child visiting our farm asked me why my horse drools so much. I knew the particular reason for this horse’s wet mouth but decided to provide a more comprehensive answer about drooling horses.

In general, horses drool because of grass sickness, poisoning, infection, dental problems, or the result of increased work. Horses that excessively drool could be experiencing a severe medical condition and requires veterinary care.

There are many things horse owners need to know about horses. The reason a horse drools and how much is normal is essential.


Why do horses drool?

Seeing a puddle under your horse’s mouth while grooming can be a little alarming. This is especially true if the pool is large. However, that doesn’t mean that something is necessarily wrong with the horse. Some drooling is to be expected, although excess drooling should be investigated.

Grass sickness

Grass sickness is probably the worst-case scenario for excessive drooling. The exact cause of this problem isn’t known, but the results are. It affects the nervous system, causing paralysis in the gut.

The horse can’t swallow the saliva, and this is often fatal. It is more common in Northern Europe and Great Britain than elsewhere, but it can occur anywhere.


There is more than one toxin that can cause excessive drooling in horses. One is sometimes found in clover, although it isn’t clover itself that poses the problem.

Instead, it is the host for a parasitic growth that will cause slobbers, the illness named for the results of a horse eating it. Slobbers aren’t a harmful disease and will go away on their own.

Fields that have been sprayed with pesticides also pose a serious threat to horses and other animals. Some states have banned the use of pesticides on land that produces livestock feed.

Banning pesticides can help prevent this sort of poisoning; however, if the horse has already eaten it, you will need to contact the vet.

Ragwort, which is a bane to those of us with hay fever, can also be toxic to horses. There is a tool called a ragwort fork that can help rid your paddock or pasture of this threat.

If you have an allergy to the plant, it would be wise to either wear gloves, masks, and goggles or get someone who isn’t allergic to clear it for you.


Whether it’s from a heavy-handed rider or the horse chewing on something that causes damage to the mouth, an oral injury can cause drooling. You’ll need to check the mouth carefully, both inside and out, to see if something is causing the problem. Once found, rest from the cause will help it heal.

If you have allowed someone else to ride your horse and they are responsible for this, you may want to see that they get educated on using the reins properly.

The most painful bit on the planet is any bit in the hands of someone who uses it too harshly. This is as much for the rider’s benefit as the horse’s. Some horses will not take kindly to less gentle handling and may well toss the rider.

Picture of a horse getting its teeth floated.

Dental problems

If you’ve ever had a toothache, you’ll understand why a horse may have some difficulties in this area. If you’ve been around babies enough, you may also have experienced tooth-cutting drools.

While looking for injuries, it might be wise to look at the horse’s teeth. Spurs on the tooth can irritate the tongue and the cheeks, just like they do ours.

To resolve this issue, call the equine dentist. Unless you are experienced in handling this problem, you may sustain some serious injuries trying to do it yourself. The horse may not bite your finger off, but the pain may knock you down, and you’d have other injuries to worry about.


If you notice your horse has bad breath to go along with the excessive drooling, an infection of some sort might be involved. Like many problems, this is one for the vet to handle.

The herbs and antibiotics humans use may not be appropriate for a horse. The type of infection will also dictate what is used to treat it.

Picture of a horse with nasal discharge.

Nasal discharge

Nasal discharge is a sign of a potentially serious problem. If food gets stuck before it hits the stomach, it can cause something called a choke. It isn’t likely to go down on its own and will require the help of your veterinarian. Horses can’t throw up, so they can’t get rid of it on their own.

Have you ever seen anything like the horse in the picture above? I hadn’t. Out of the blue, we noticed him with white foam on his muzzle and in front of his stall. I was stumped, so we called a vet. He had never seen this condition either and didn’t have an answer.

We watched the horse throughout the next couple of days and noticed he pushed his neck on the stall gate and strongly sucked in air. This created the white foam, so we tied some string across the gate to prevent him from sticking his head out, and the foam ceased.


Both excitement and fear can cause excess salivation in horses. For fear, it starts because the startle response in horses causes their mouths to go dry. When they calm down, they produce excess saliva to rehydrate their mouths. This is absolutely normal.

Morning sickness

Pregnancy does a lot of weird things to the female mammal. Hormones are released that can play hob with emotions and cause stomach difficulties. These are most common in the first third of the pregnancy. Your vet can tell you what to do to help keep the mare comfortable.

Picture of my horse grazing.


Weather can play a role in how much a horse drools. They lose some of the body heat caused by hot weather through the creation of extra saliva. A horse will need access to fresh water and a cool place to stay in the heat in order to avoid heat-related illnesses.

Increased work

The more the horse is called on to do, the more it will create excess saliva. It is common to see and perfectly normal. Remember that if a horse is over warm after a workout, it needs to cool down before heading for a water drink. Losing saliva from work will make it want to drink.

There are a few rare reasons for a horse to drool excessively, as well. Diseases such as Borna Virus can be a cause. It isn’t all that common, but it is very similar to polio in its actions. It is usually fatal if contracted. Most of the spreading of the virus is through the urine of infected animals.

Another virus, called equine viral arteries, may also cause excessive drooling. The problem here is mostly with mares, and it is most commonly spread through mating.

If a pregnant mare catches it, she will most likely abort because the disease and pregnancy don’t mix well. Fortunately, there is a vaccine available in the U.S.

Below is a helpful YouTube about drooling caused by eating clover.

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