Foaming at the mouth is common in horses, mainly when they are being ridden or eating. It is often seen as a positive sign, indicating relaxation and comfort. However, in some cases, foaming or frothing may indicate stress, tension, or a medical issue that requires attention. As horse owners and riders, it is essential to understand why a horse may foam at the mouth and when it may be something to be concerned about. A horse can foam at the mouth for a variety of reasons: the top three reasons are chewing food, the bit, and medical issues.
Understanding equine foam - Saliva and Sweat
Horses have a protein called latherin in their saliva and sweat. Latherin is a surfactant that reduces the surface tension of liquids, allowing them to spread quickly.
As horses sweat, the lathering helps the sweat coat the hair evenly and quickly, increasing the sweat's evaporation rate to cool your horse. In saliva, the latherin helps a horse chew and digest their forage.
Foam is created when the latherin protein in sweat and saliva meets friction from movement. Horses are unique individuals, with varying amounts of latherin in their bodies, and they will also vary in how much they play with or resist the bit. You typically see bubbles around a horse's mouth, but some horses produce so much foamy saliva that it drips in on their legs as they exercise.
3 most common reasons why a horse is foaming at the mouth
A horse will foam at the mouth with enough friction. Why and how that friction happens can result from many things, including stress, medical issues, relaxation around the bit, eating a snack or grazing, dental issues, or any other situation in which their mouth movements create friction with latherin.
1. Chewing food
The most natural cause of a foamy mouth is eating. Grazing, hay nets, horse feeds, and horse treats stimulate saliva production, and chewing creates foam so that the horse does not get a dry mouth while eating. You can usually see the white foam unless your horse only dribbles a little bit while eating. Horses will also excessively foam when eating clover with a certain fungus. The clover slobbers, as they are known, boost saliva production due to the fungus. Sometimes, a horse will become dehydrated as they are drooling so much.
2. Foaming at the bit
Most equestrians are aware that foam occurs when a horse is wearing a bit, especially in dressage horses. Ideally, a horse is soft, relaxed, and gently chewing the bit while being ridden. You may see some foam then; it depends on the horse. Conversely, a tense horse fighting or gnawing with the bit, having tension, or objecting to being ridden may also create visible foam and extra saliva. The presence or absence of excess salivation alone does not indicate whether a horse has accepted the bit, is ridden too hard rein contact, or is stressed. Look at your horse's overall demeanor, fitness, bridle fit, vital signs, hydration, weight loss and overall health when deducing if your horse's mouth foam indicates something positive or negative.
3. Medical reasons for frothy mouths
Horses that grind their teeth, those with dental issues, or stressed horses may have foamy lips. Some horses foam while experiencing choke, a blockage in the esophagus that prevents them from swallowing. Sometimes, you see foam coming from the nostrils during choke, too.
Viral diseases such as rabies and vesicular stomatitis cause foaming at the mouth. Rabies affects the nervous system, interfering with chewing and movement, causing saliva to dribble out. Vesicular stomatitis creates ulcers in the mouth, and excessive salivation often accompanies this.
What can you do about a foamy mouth when ridden?
It's up to you, your trainer, and perhaps an expert bit fitter to determine if your horse's foamy lips signify relaxation or stress during exercise. Relaxed horses will feel soft in the reins, have an easily bendable body, work from their toplines, and generally be pleasant. Tense, foamy horses will feel hard and stiff, resist your aids, and hold tension. You may also experience tail wringing, teeth grinding, and kicking out. This might be a training issue, or your horse tells you something in their body doesn't feel great.
You may also experience a stiffer horse without any foam, which will start to release bubbles as it relaxes. It can be a sign of training progress! As long as you ride with a soft hand, especially when using double bridles, you should nott be concerned if your horse foams when ridden. Excessive foam can often be a sign of relaxation.
When to consult a Veterinarian
When a horse suddenly starts to have a foamy mouth when they usually don't have one, it's a sign to call your vet and discover possible reasons. You want to rule out any serious conditions, including medical issues, dental problems, liver diseases, black patch disease, or infections, and create a treatment plan accordingly. Some toxic plants can cause horses to foam at the mouth and grazing on too much red clover can develop excessive drooling. It is therefore always important to inspect your horse's pasture for any presence of clover.
In horsemanship, it's always a good idea to notice new behaviors and signs as communications from your horse. Keep your horse's welfare the top priority, gather information from their bodies and habits, and work with experts and vets to determine how your horse feels.
