Woman with stethoscope next to a horse

Anhidrosis in Horses: What To Do If Your Horse Is Not Sweating

Reviewed by Dr. David J. V. Drum DVM MS

With summer comes competitions and traveling, but the temperature increase can be hard on horses. You’re probably aware that horses sweat more in the summer, just like us. But did you know that a horse can get so hot that it stops sweating?

As the weather warms up and the humidity increases, it’s important to monitor your horse’s health and educate yourself so you know when something’s wrong. In this guide, we’ll cover what you should do if your horse stops sweating.

What is anhidrosis in horses?

Anhidrosis is the decreased ability or inability to sweat when the body’s temperature increases. This condition is also known as non-sweating disease or dry coat syndrome. It tends to occur in horses that live in hot and humid climates where sweat does not evaporate as easily. While some horses regain the ability to sweat when the weather cools down, others experience a chronic form of anhidrosis where their sweat glands degenerate to the point that they can no longer produce enough sweat.

Do horses have sweat glands?

Horses do have sweat glands densely packed within their skin. Sweat glands are rich in blood supply and nerves so that they can communicate with the brain when a horse needs to sweat. A horse’s sweat consists of water, electrolytes, and proteins that protect the skin and saturate the horse’s hairs to help sweat evaporate.

Horses maintain their body temperature in two primary ways: sweating and respiration. When a horse’s body temperature rises, the brain activates sweat production. The sweat absorbs heat from the horse’s body, then evaporates to remove the heat, cooling the horse. Horses also regulate body temperature by increasing their breathing rate. This allows heat to be released from their airways. However, less than a quarter of a horse’s body heat is dissipated through respiration.

Why is sweat important?

Sweat is a horse’s primary method of thermoregulation, or maintenance of the core body temperature. Horses need to sweat to keep cool in the heat and when they exercise. If a horse has anhidrosis and cannot sweat, it’s unable to effectively cool its body, posing a risk for heatstroke.

How prevalent is equine anhidrosis?

The prevalence of anhidrosis in horses varies by region, with horses living in areas with hot and humid climates at greater risk. This includes Gulf Coast states like Florida, where 2% of horses studied had anhidrosis. Previously, people believed that anhidrosis resulted from the stresses of a horse adjusting to a new climate, but now we know that horses born and raised in hot, humid climates are just as, if not more, susceptible.

Several other factors affect the prevalence of equine anhidrosis. Performance horses that consistently work hard in hot climates are most likely to suffer from anhidrosis, but any horse can be affected. While horses of any breed, age, sex, or color can develop anhidrosis, it’s most common in Thoroughbreds and Warmbloods. Horses with a family history of anhidrosis also have a greater risk.

What causes anhidrosis in horses?

Experts do not know for sure what causes anhidrosis in horses, but they suspect hormonal and neurological factors are involved. Basically, experts suggest that sweat glands stop responding when they become overly stimulated by the overproduction of the neurotransmitters that prompt sweating. These excess signals are, of course, triggered by exposure to hot and humid environments.

One theory suggests that once the sweat glands adapt to the increased level of epinephrine (also known as adrenaline, the hormone that stimulates sweating) in the blood, they stop responding to it. 

Others attribute anhidrosis to hypothyroidism or low chloride concentrations, which also affect sweat gland activity. For instance, an antibiotic used to treat an infection in foals has been known to cause overheating and anhidrosis. This is likely due to blocked chloride secretion which inhibits the transportation of water and salt to sweat glands. Another potential cause is blocked water flow to sweat glands due to the absence of a water channel protein called “aquaporin-5.”

Although many theories about what causes anhidrosis in horses exist, they have yet to be confirmed. Experts continue to research the causes of equine anhidrosis, hoping to find a way to prevent it from affecting horses in the future.

Symptoms of equine anhidrosis

A number of symptoms can identify a horse’s inability to produce enough sweat. These symptoms may vary depending on the horse and the severity of the condition. For example, a horse may continue sweating in some areas but lose sweat production where sweat glands are most active. Some horses’ sweat production increases before the onset of anhidrosis, while others experience a gradual decrease in sweating. Because signs of anhidrosis are expressed differently from horse to horse, it’s important to watch for any potential symptoms.

As you monitor your horse’s health in the summer months, look out for the symptoms of acute and chronic anhidrosis listed below.

Acute anhidrosis symptoms

Some horses suffer from acute anhidrosis in the warmer months and return to normal sweating when the weather cools down. Your horse may be suffering from acute anhidrosis if it shows these signs:

  • Minimal to no sweat production in situations that would usually cause sweating
  • Increased respiratory and heart rates
  • Inability to cool down to a normal temperature (99.5 to 101°F) within 30 minutes after exercise
  • Dry, hot coat after exercise
  • Hyperthermia (overheating)
  • Decreased water consumption
  • Lower performance in high temperatures

Chronic anhidrosis symptoms

In chronic anhidrosis cases, horses begin to experience irreversible changes in their sweat glands. If your horse is developing chronic anhidrosis, they may show these signs:

  • Loss of sweat production
  • Dry, flaky skin
  • Hair loss
  • Increased water consumption
  • Weight loss
  • Fatigue, lethargy, and poor performance

Learn more: Horse Hydration 101: How Much Water Should Your Horse Drink in a Day

What to do if your horse stops sweating

If you notice your horse stops sweating or develops other signs of anhidrosis, you should consult your veterinarian. He or she will examine your horse’s behavior and look for physical symptoms of anhidrosis. Your veterinarian might also test your horse’s ability to sweat by injecting terbutaline to stimulate the sweat glands.

As soon as your horse begins showing symptoms of anhidrosis, move your horse to a stall or shaded paddock, and provide plenty of water. Anhidrotic horses are at risk for overheating, so it is important to keep them as cool as possible to help them regulate their body temperature.

Treatment options for equine anhidrosis

Move to a cooler climate

The only remedy for anhidrosis with proven success is moving the horse to a cooler climate. While this is the most promising approach, it is often not feasible for the owner. If your horse is suffering from anhidrosis and cannot be moved to a more temperate climate, you will need to closely monitor his health and help him regulate his body temperature.


Horses that don’t sweat need help regulating their body temperature. You can use the following methods to help prevent your horse from overheating:

  • Always provide cool and clean water to drink
  • Offer a pond or large water trough they can use to cool off
  • Minimize heat exposure during the day
  • Install air conditioning or misting fans in their stall and paddock
  • Exercise your horse during the coolest hours of the day
  • Hose your horse down before and after exercise


Supplement your horse’s diet with electrolytes to help your horse maintain the right balance and encourage hydration. You can do this by adding electrolytes or salt to their feed.


There is no proof that supplements are actually effective at relieving anhidrotic symptoms. However, some owners find that supplements containing iodine, B vitamins, Vitamin E, or L-tyrosine (an amino acid involved in the production of epinephrine) help their horses sweat more normally.

Acupuncture and herbal medication

A study from the University of Florida concluded that acupuncture combined with herbal medication can effectively improve sweating in some acutely anhidrotic horses. However, the benefits lasted for less than four weeks after the treatment ended.

Should you give your horse beer to treat anhidrosis?

Giving your horse beer to treat anhidrosis is a strictly anecdotal practice. While it will not necessarily harm your horse, it will also not help your horse resume sweating.

During the hottest time of the year, our equine companions need more care and attention than ever. It’s important to understand the first signs of anhidrosis, the risks involved, and how to care for horses that can’t sweat. Anhidrosis can be challenging to navigate, but every effort counts in eliminating the risks it brings. With diligence and care, we can ensure that our horses stay comfortable, healthy, and ready to take on summer adventures.

The Farm House Tack has everything you need to look after your horse’s well-being. Shop our grooming and stable supplies to find the essentials for keeping your horse happy and healthy. 

Learn more about horse care with our other guides:

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