The horse may play around more with the water pail, choose to stand in shade while other horses are grazing, or roll in water and mud to cool down. There is no specific treatment for horses with anhydrosis. The first step is management. Ride your horse in the coolest part of the day and keep him out of the sun. In extreme cases, horses may have to be stalled in air conditioning.
Some owners decide to relocate their horse to a part of the country with less heat and humidity.
Endurance horses and race horses might need to find a different job rather than being highly competitive athletes. Changes in diet can reduce heat production as well. Digestion of proteins and forages generate a fair amount of heat. Go to a high-fat diet. From a caloric standpoint, it is more easily assimilated with less heat generated by digestion.