Anhydrosis is the inability of a horse to produce normal amounts of sweat. Some horses sweat normally in spring, but develop anhydrosis in the summer as heat, humidity, and workload increase. Horses depend heavily on sweating to regulate body temperature. Many horses raise their body temperature to around 104 degrees during training. Exposure to a temperature of 106 degrees may cause brain damage.
Sweat is critical so that evaporation cools the horse.
Sweat glands of horses with anhydrosis and of normal horses look the same under a microscope. Something is interfering with the physiological, chemical, or neural transmission. One is that it is a metabolic failure and another is that the sweat glands become fatigued-perhaps because the climate horses are worked in requires more sweating than the climate where they were raised. Besides a decreased amount of sweat or a lack of sweat, your horse may show intolerance for exercise. They'll refuse to go forward or they'll pant.