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Why Do Dressage Horses Foam At The Mouth?

Dressage is considered the ballet of English riding. At the highest level of competition, riders wear fancy coats with tails and, until recently, top hats. The horses are as shiny as a waxed wooden floor, their mane done up in complicated braids. But as they compete, dressage horses foam at the mouth as if a rabid squirrel. Why?

Dressage horses foam at the mouth due to excessive saliva. It’s a positive sign that the horse is relaxed and in the correct position. Sometimes the foam is tinted green or orange, especially during training. The tint means the horse sneaked in a snack break, sometimes with their rider’s permission.

Horses lick and chew when they are relaxed. One of the key hacks to calm a horse that has been spooked is to get the animal to eat. Thus, when a horse is working correctly, the position creates pressure in the mouth. When the horse relaxes and chews softly, this action, combined with the pressure, creates extra salvia, which can foam.

Latherin: Why Horses Foam At The Mouth

All horses that are being ridden, regardless of the sport, can potentially foam at the mouth. Even horses not being ridden sometimes foam when they’ve got a particularly chewy snack in their mouth. Part of the reason horses’ salvia can become so foamy is due to a surface sweat protein called latherin.

Horses create latherin in their skin and salivary glands. Latherin reduces water’s surface tension, so it is believed it helps a horse’s sweat wet their water-resistant coat to cool them. But the reaction is similar to how detergent works and thus creates a slight foaming film on the fur and creates even more around the mouth.

On The Bit: Why Horses Foam At The Mouth

Ideally, when riding a horse, the rider should have the animal “on the bit.” This is about form, not the bit, so this form is achievable bitless. Horses do this naturally in the wild or pasture when relaxed. The head is lower, the neck long, and the back is rounded.

A high head hollows the back. The horse could be scared; hence the neck stiffening, head up, alert to dangers. On the other hand, the horse could just be curious, checking out all the new faces in the stands, wondering if they have carrots. The horse could also be bored and is scoping out alternative actives to the rider’s agenda.

Regardless of why the horse is impersonating a giraffe, the animal’s focus is not entirely on the rider and the actual work. Horses sometimes trip doing this, the same way a toddler getting distracted by a passing bird stumbles on their own feet. The ride is not as smooth, and the horse is not optimally engaging their muscles.

A horse working off the bit is like going to the gym and doing your exercises with bad form. When on the bit, the horse brings the head down, curves the neck slightly (not too much), lengthening the neck’s top line, and rounding the back. As a result, the horse has better balance and uses their muscles in an optimal matter.

A horse looks graceful and elegant when on the bit. This is essential in dressage. A horse and rider can still get over fences and race along a trail off the bit and still win. It isn’t ideal, but there are no points lost in these disciplines due to lack of beauty. However, in dressage, the competition is all about correct form and elegance.

When a horse is on the bit, the animal relaxes its jaw and begins to subtly (or not so subtly) chew. There is slight pressure on the bridle and bit, making slightly more weight in the rider’s hands. This is called contact, which the rider hopes to maintain, allowing rider and horse to be in sync.

But it also produces excess salvia. The chewing, the extra weight, the latherin all work together to create foam that looks out of kilter with the rest of the elegant look. But it is actually a good thing. Except when it isn’t.

8 Alarming Reasons Horses Foam At The Mouth

Generally, a foaming mouth is nothing to worry about and, in fact, a positive sign. But there are times it is a sign something is wrong. Here are eight problems that may be creating unwanted excess foam.

1. The horse has something stuck in its mouth

This is usually not a big deal. Rider pitches up to the stable to be greeted by a foamed mouth horse that hasn’t eaten anything that should cause it. But just like humans, horses sometimes get food stuck in their gums or teeth. It is usually a piece of hay, and once removed, problem solved.

2. The horse is stressed

Intense fear and flight can create excess foam. Sometimes the “fear” is a silly thing. For example, a horse we know is terrified of cows, and a cow got into the animal’s pasture. The cow was ignoring the herd as it grazed. But the cow-crazed-horse wasn’t having it. So, the cow was gently encouraged to leave.  

However, a horse can also become stressed if being overexerted and poorly ridden. Stable owners and riding instructors need to shut that nonsense down if it is happening. It’s fairly obvious, as the horse will be foaming but not in a relaxed “on the bit” manner, but uneasy and behaving erratically.

3. The horse has clover slobbers

Clover slobbers are an unattractive result of a horse eating legumes infected with Rhizoctonia leguminicola, a fungus. The fungus contains slaframine, which irritates horses much like mosquito bites irritate humans. Very rarely is this a big deal, but if you have concerns, contact your vet.

4. The horse has mouth ulcers

Mouth ulcers might mean a vet check or calling the dentist. It depends on the injury. Sometimes it is due to something as simple as a seed getting caught in the gums and causing a sore.

If the ulcers are clearly from a poor fitting bit, bridle, or poor riding, that needs to be fixed immediately. Allow the horse to completely recover before any new tack is put in the poor animal’s mouth.

5. The horse has a virus

Yes, technically, rabies is a virus. However, if your horse is vaccinated, that’s not the conclusion you jump to, but still, call the vet. It is probably vesicular stomatitis that is transmitting by those awful biting flies. The virus can cause lesions on the body, including muzzle, lips, and tongue.

The virus is not fun for the animal, but it is rarely fatal. Again, call the vet and get the animal treated.

6. A bacterial infection or contact with a toxic substance

Just like toddlers and pets get into things they should not, so do horses. There are many bacterial and toxic substances out there, but in the end, it all boils down to: call the vet.

Knowing what caused the issue will make the vet’s job easier, so keep it if you have the item. (But away from the horse.)

7. The horse is choking

8. The horse has a dental problem

Few enjoy going to the dentist; this includes horses. But it is necessary, and sometimes a broken tooth or other dental issues cause excess saliva and foam. So if your horse is due to see the dentist, give them a call. Likewise, if you have ruled out all other options, give the dentist a call.


A horse foaming from the mouth, especially during dressage, is considered a positive sign. However, there are rare occurrences when the foam is a clue that something is amiss. When in doubt, call the vet.

Anrie Diedericks

I've been around horses since I was 6 years old and started competing at the age of 9. Horses are my greatest passion and I am thrilled to be able to share my 23 (and counting) years of experience and knowledge with you.

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