Horse Anhidrosis Welfare and Management

Anhidrosis — the inability to sweat — is a serious welfare condition in horses in hot, humid climates that causes dangerous heat retention during exercise.

Key Facts

Anhidrosis affects an estimated 6-20 percent of horses in subtropical and tropical climates
Affected horses cannot thermoregulate through sweating, causing dangerous core temperature elevation during exercise
The condition may be partial — with reduced sweating — or complete with no visible sweat production at all
Hot, humid environments with little seasonal variation appear to predispose to anhidrosis over multiple seasons
Clinical signs include elevated respiratory rate, elevated body temperature after minimal exercise, and dry skin
Moving affected horses to cooler climates sometimes resolves the condition over weeks to months
Supplementation with electrolytes and one AC (acetylcholine supplement) shows inconsistent evidence but is widely used
Exercise restriction and access to cooling systems including fans and cool water are welfare management priorities

Welfare Considerations

Anhidrosis creates a genuine welfare emergency in affected horses: the inability to dissipate heat through sweating means that even modest exercise creates dangerous core temperature elevation that causes distress and risks heat stroke. Horses in hot climates with anhidrosis cannot be safely exercised during warm months without cooling support, and asking anhidrotic horses to work in heat causes welfare harm through heat stress and associated physiological distress. Management priorities include exercise restriction during the hottest periods, access to shade and active cooling systems, and regular temperature monitoring. In some cases, relocation to cooler climates is the most welfare-positive option, particularly for horses in severely affected states.

What You Can Do

Recognize anhidrosis signs early — monitor respiratory rate and skin sweating pattern after minimal exercise in hot weather
Restrict exercise during hot and humid conditions for horses with confirmed or suspected anhidrosis
Provide shade, fans, and cool water access as welfare priorities for anhidrotic horses
Monitor rectal temperature after any exercise to detect dangerous heat retention before it becomes life-threatening
Consult a veterinarian about supplementation and management strategies for confirmed anhidrosis
Consider relocating severely affected horses to cooler climates if welfare cannot be maintained in the current environment