Why is my Horse Sweating? Signs and Dangers of Horse Sweat

Sweat is normal for horses who have been working

A sweating horse is relatively common, but in some cases, can be dangerous. It’s essential that you keep an eye on your horse and recognize the danger signs that can accompany a sweating horse. 

Do horses sweat? Like humans and other animals with sweat glands, horses sweat to lower their body temperature and relieve heat build-up. Sweating is normal and healthy for horses, but it can indicate danger or illness in some situations. If there is no apparent reason why a horse is sweating, such as temperature or exercise, be alert and watch for other signs. 

Did you know? 

Breathing helps a horse regulate its body temperature to some extent. But, once your horse exceeds a certain level, he needs to sweat to stimulate evaporative cooling. When this happens, the hypothalamus emits signals to stimulate the sweat glands into production. The hypothalamus gathers information from thermal receptors in the skin and organs and regulates internal body temperature. 

When sweat evaporates from the skin, it takes away heat and helps restore the horse’s body to its average temperature of 99 to 101 degrees Fahrenheit. 

Causes of Horse Sweat and Their Signs

It is natural for a horse to sweat in certain situations. Hot temperatures and exercise induce overheating in horses, and they will sweat. But, in some cases, sweating can become excessive and dangerous:

  • Hot weather: When the ambient temperature is high, horses will sweat even if only grazing.
  • When being ridden or exercised: The movement of the horses’ muscles generates enough heat to raise the horse’s core temperature by as much as 1.8° F every minute. The amount your horse will sweat will depend on the weather, the horse’s fitness levels, and the duration and intensity of the training session. An unfit horse that’s ridden for a long time in hot weather can lose up to four gallons of sweat every hour, so keeping him hydrated is essential. 

In other instances, a sweating horse may indicate dangerous situations for your horse:

  • Pain or distress

Discomfort can cause a horse to sweat, and sweating is a sign of numerous health conditions, including Cushing’s syndrome, laminitis, botulism, and colic.

  • Illness

Equine influenza, Potomac Horse Fever, strangles, and viral infections can all cause a horse’s temperature to increase. As the horse’s body struggles to regain its normal temperature, it stimulates the sweat glands and maximizes blood flow to the skin. Both processes are designed to dissipate heat and reduce fever. 

Horse Sweat Differs From Human Sweat

Human sweat consists almost entirely of water and contains only tiny amounts of salt, sugar, ammonia, and urea. On the other hand, horse sweat has much higher concentrations of proteins and electrolytes, such as calcium, chloride, magnesium, potassium, and sodium.

Horse sweat also contains latherin, which isn’t in human perspiration. Latherin is an ingenious equine adaptation that reduces the surface tension of water, facilitating the movement of moisture away from the skin and improving both evaporation and cooling processes. 

Horses have thick, waterproof coats that inhibit the movement of sweat from the skin to the hair’s surface, so they need latherin to make the process of evaporative cooling more efficient. 

The presence of latherin causes horses to produce that white, lathery sweat we often see on racehorses. Latherin responds to friction. So, it first appears wherever there is rubbing. It can occur between the horses’ back legs, under his tail, and where the reins lie against the sides of his neck.

While latherin is a valuable component of horse sweat, the electrolyte content can be troublesome. Horses need electrolytes to maintain their normal fluid balance and circulatory function. Electrolytes also trigger nerve functions, maintain the body’s acid-base balance, and facilitate muscle contractions. 

Is horse sweat dangerous to a horse? Excessive sweating can be very dangerous to a horse. If a horse loses too many electrolytes through excessive sweating, those deficiencies can cause fatigue, loss of appetite, lethargy, muscle weakness, and reduced water intake.   

In addition to losing vital electrolytes, the more a horse sweats, the more water it loses. This leads to a reduction in the blood’s water or plasma content. This process forces the heart to work harder and faster to maintain the body’s oxygen levels. It can cause the cardiovascular and thermoregulatory systems to compete for fluids. 

A horse that suddenly stops sweating is in grave danger. The horse will sweat less or even stop altogether to conserve the fluids needed to maintain a healthy blood volume and pressure.

This often causes dehydration, hyperthermia, or hypovolemia. Hypovolemia is a condition in which blood plasma or liquid content drops too low. These conditions can be severe and even potentially life-threatening, but dehydration probably presents the most significant risk of all.

Horses aren’t as quick to feel thirsty as humans, so they are more susceptible to dehydration which, in severe cases, can cause serious health problems such as kidney failure and colic.

How To Tell If Your Horse Is Sweating Normally or Excessively

The easiest way to tell if your horse is dehydrated is to pinch a fold of skin on his neck or shoulder and pull it out gently. If your horse is dehydrated, the skin will remain in position once released as water loss has reduced the skin’s elasticity. 

Your horse may also be more lethargic and less responsive than usual.

If you notice any signs of dehydration in your horse, you should stop exercising him immediately and lead him to a shady area with access to plenty of water. Oral electrolytes may help stabilize his condition, but if a horse has been sweating excessively and is unwilling to rehydrate himself by drinking, you’ll need a vet to administer intravenous isotonic fluid therapy.  

example of normal horse sweat (1)
This photograph shows my Arab gelding in his winter coat after doing an hour’s moderate exercise. The temperatures are between 65 – 68° F. This sweat level indicates a horse whose temperature regulation is functioning and who is working at an appropriate intensity for his fitness.

Underlying Issues That Cause Excessive Sweating In Horses

Excessive sweating could merely be a sign that your horse has been working hard or that it’s a hot day and he’s standing in a field with limited shade available. 

In these circumstances, it’s natural and normal for a horse to sweat, but it can indicate an underlying problem or health concern in other situations. Excessive sweating, or diaphoresis, can signify Cushing’s syndrome, although it’s not a common presenting complaint. 

Both botulism and colic can cause diaphoresis, but it will usually be accompanied by other symptoms, such as loss of appetite, pawing the ground, or trying to lie down. Excessive sweating is also associated with severe laminitis. In these instances, horses produce sweat in response to pain and distress.  

How to Treat A Horse That Sweats Excessively

If you’re concerned that your horse is sweating too much or sweating at inappropriate times, you need to gain a clearer idea of what stimulates it. You can then share that information with a vet and find a solution to the problem. 

Does your horse sweat while eating or after he’s finished a meal? Is your horse’s sweatiness associated with hot weather or intensive exercise? Does your horse mainly sweat at night? 

You can also take your horse’s temperature when he’s sweating to see if that’s also elevated. Bear in mind that a horse’s normal temperature will fluctuate but shouldn’t stray too far from the 99 to 101 degrees Fahrenheit range.

If your horse is sweating more under saddle than usual, measure his heart rate after a period of intense exercise and then again 10 minutes later. If his heart rate hasn’t dropped to around 60BPM, he may not be fit enough for that level of activity. Or he could be experiencing some respiratory, metabolic, or heart-related problem. 

Watch your horse’s rib cage. Monitor his breathing, listening out for any signs of respiratory discomfort, such as shallow breathing, ragged breaths, or crackly noises when he breathes.

From this information, your vet will know how to proceed with a diagnosis. 

However, there are other factors to consider depending on what appears to simulate the sweating.

How To Deal With a Horse That Sweats At Night

When horses are sweating at night or during the winter, it could be something as simple as a poorly ventilated stable or something more complex like diet. Without proper cleaning, a stall can be a breeding ground for humidity and could easily cause your horse to sweat at night, especially if he’s lying down. 

To help a horse that sweats at night:

Improve ventilation in the stable

If your horse is sweating in his stall, look around to see if there are any windows or vents you can open to allow for the flow of cool air through the stable. If not, you might want to think about moving your horse to a stable with better ventilation or renovating his existing stall to rectify the situation. 

Change your horse’s bedding.

Clean your horse stall daily, taking care to remove any wet or soiled bedding. A deep litter bedding system is ideal for winter. That’s because it keeps your horse warmer. And, in the hot summer months, a bed of deep wood shavings will help insulate him against the ground heat.

Adjust your feeding regime

Feeding your horse a meal with a high starch or sugar content late in the day might contribute to sweating during the night. Thus, a simple change of diet or feeding regime can quickly solve the problem.  

How To Cool A Horse Down Quickly After Exercise

It’s normal for a horse to sweat when exercising or on a hot day, but that doesn’t mean you can’t offer him some assistance. For example, endurance horses need to cool down quickly, so their heart rates drop to the required 60 BPM within 20 minutes after completing each leg of the ride. As a result, endurance riders and their grooms use various methods to cool their horses quickly. 

According to the International Federation for Equestrian Sports (FEI), applying large quantities of cold water to all parts of your horse’s body is one of the best methods for bringing his temperature down quickly. 

You don’t need to focus on the large blood vessels as cooling by evaporation works by cooling the blood in the small blood vessels in the skin, not the large ones in the neck or between the legs.

At the end of each leg of a ride, you’ll often see grooms frantically dousing horses with water and scraping it off again. They do this because they believe that water left on the horse heats up and insulates the horse, increasing his body temperature and countering the cooling effect. 

Dr. David Marlin has disproved this theory by conducting a thermal imaging exercise. According to him, scraping is a waste of time and energy. He states that you can cool down your horse more quickly by applying more cold water than by scraping.

In addition to cooling your horse with cold water, you should encourage him to walk. This promotes the flow of blood to the skin. It helps the body cool via convection. As the horse moves, the air movement around him also facilitates evaporation, helping his body temperature drop more quickly.

Research into different cooling techniques established that showering your horse continuously with tap water (average 78°F) is more effective than intermittently applying cold water (50°F) and scraping between applications. 

A hot horse will cool more quickly if he has access to plenty of drinking water, while you can counter the effects of excessive sweating with the administration of electrolytes.  

More worrying than a horse that’s sweating too much is one that’s unable to sweat at all.

horse lathering after extreme sweating (1)
Lather builds up in the creases and areas where it’s harder for sweat to run off.

How To Manage A Horse That Can’t Sweat: Coping With Anhidrosis

Anhidrosis is a relatively common condition in horses, affecting between 6-11% of the world’s horse population. 

Unable to cool themselves through sweat production, horses with anhidrosis will pant to reduce their body temperatures. While the movement of cool air across his respiratory tract helps to some degree, it’s not an efficient method of thermoregulation. As a result, the horse’s body temperature can increase to 102°F even when he’s resting. 

Any attempt to exercise such a horse will cause his body temperature to rise even further. This puts the horse in danger of developing heat cramps, heatstroke, or even brain damage. (Check out Is Summer or Winter More Dangerous For My Horse?)

Anhidrosis is a dangerous and potentially fatal disease for which there is no known cure. Over time, a horse suffering from chronic idiopathic anhidrosis will sustain damage to his sweat glands. This makes the disease difficult to reverse and even more challenging to treat. 

Over the years, owners of horses with anhidrosis have tried everything, from cans of Guinness to feed supplements and electrolytes, but with little success. There is some evidence suggesting that the vitamins and yeast strains in dark beers support the metabolic pathways, encouraging them to function correctly. But, when evaluated critically, they appear to do little to improve anhidrosis.

Both acupressure and acupuncture can similarly stimulate the sweat glands and reduce symptoms of anhidrosis, but the effects are generally short-lived. 

A supplement called One AC is proving a more effective in the treatment of anhidrosis. Some vets have reported a 30 to 70% success rate. The supplement, which researchers at the University of Florida have extensively tested, contains cobalt, L-tyrosine, niacin, and vitamin C. 

Biochemist Raymond LeRoy designed One AC. He believes that the depletion of dopamine in the brain is responsible for anhidrosis. The supplement provides horses with the materials needed to compensate for that depletion. 

Conclusion

While sweating is a natural response to intensive exercise and hot weather, excessive sweating can cause problems as the horse loses essential fluids and electrolytes during the process. A horse that can’t sweat at all is in even greater danger, and, as yet, there is no known cure for anhidrosis.

By checking your horse’s temperature and heart rate regularly, keeping an eye on his breathing, and cooling him off with cold water after exercising on a hot day, you can ensure he’s sweating normally and not in danger of developing heat stroke or dehydration.  

You may also find this article helpful How Hot Can Horses Tolerate- Safety In Extreme Heat.

Nicky Hoseck

I’ve been around horses since the age of six and, 15 years ago, leapt at the chance to leave behind my London-based career in journalism and start life on a small-holding in South Africa. Sharing my experiences with horses, goats, and other farm animals allows me to flex my writing skills and help others find their way to a happy, healthy herd.

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