09/07/2026
Anhidrosis (sometimes called non-sweating syndrome) is a condition in which a horse produces little or no sweat, making it difficult to regulate body temperature. Because sweating is the horse’s primary cooling mechanism, affected horses are at much greater risk of overheating, particularly during exercise or in hot, humid weather.
Here are the key facts:
What is anhidrosis?
Anhidrosis is the partial or complete inability to sweat normally. It can affect horses of any breed but is most commonly seen in horses living in hot, humid climates.
Why is sweating so important?
A horse generates tremendous amounts of heat during exercise. Sweat cools the body through evaporation. Without adequate sweating, core body temperature rises rapidly.
What causes anhidrosis?
The exact cause is still unknown. Current research suggests the sweat glands become less responsive to stimulation, possibly from prolonged exposure to heat and high levels of circulating stress hormones such as adrenaline. It is likely a multifactorial condition.
Which horses are most at risk?
* Horses living in hot, humid climates
* Horses worked frequently in warm weather
* Performance horses
* Horses that have recently moved from cooler to hotter climates
Common signs include:
* Little or no sweating
* Rapid breathing that persists after exercise
* Elevated body temperature
* Slow recovery after work
* Poor performance
* Lethargy
* Seeking shade constantly
* Reluctance to exercise
* Warm, dry skin despite being overheated
Why is it dangerous?
Without sweating, horses cannot dissipate heat efficiently. Their body temperature may continue rising, increasing the risk of heat exhaustion, heat stroke, organ damage, collapse, and even death if not treated promptly.
How is it diagnosed?
Veterinarians often diagnose anhidrosis based on the horse’s history and clinical signs. Specialized sweat gland stimulation (intradermal terbutaline) tests can help confirm the diagnosis.
Can it be treated?
There is no universally effective cure. Management focuses on reducing heat stress:
* Exercise during the coolest parts of the day.
* Provide shade and excellent ventilation.
* Use fans and frequent cold-water cooling.
* Allow unlimited access to fresh water.
* Replace electrolytes as needed.
* Reduce workload during hot, humid weather.
* Some horses improve after moving to a cooler, drier climate.
Does it ever resolve?
Some horses recover during cooler months or after relocating to a cooler environment. Others may experience recurring or permanent problems.
Prevention
Because the exact cause is unknown, there is no guaranteed prevention. Good heat management, gradual acclimation to hot weather, maintaining hydration and electrolyte balance, and avoiding excessive heat stress may help reduce risk.
Quick Facts
* Sweating is the horse’s primary cooling mechanism.
* Horses with anhidrosis are often called “non-sweaters.”
* It is most common in hot, humid regions.
* Performance horses may be affected more frequently because of increased heat production.
* A horse that is hot, breathing hard, and not sweating should be considered a veterinary emergency until proven otherwise.
Anhidrosis is one of the most important heat-related conditions horse owners should recognize because early intervention can prevent life-threatening heat illness.
https://koperequine.com/24-interesting-facts-about-anhidrosis-in-horses/
