Horses, like humans, sweat to cool themselves in warm weather and during periods of exertion. In hot climates, especially humid ones, failure to sweat often means that they are prone to over-heating and cannot be worked. This condition is called anhidrosis.
It is unknown what causes anhidrosis and treatment is difficult. There may be a genetic component to which horses develop anhidrosis, but horses with no history of the condition in their families can also be affected. It can be complicated to diagnose because some horses experience only a reduction in sweating but not a total absence of perspiration.
Left untreated, anhidrosis can sometimes be fatal. However, the condition is usually much less dramatic. Horses with anhidrosis tend to exhibit poor performance because sweating is the normal method of cooling the body. When the body temperature reaches a certain point, it triggers the horse to stop moving so that it can cool down. This can lead to poor performance issues in sport horses.
Because anhidrosis is not a dramatic disease, there has been limited support for research on how to treat it. Grant money has typically gone to research on equine issues that were considered more urgent. However, universities are doing studies to investigate whether acupuncture could help horses with anhidrosis start sweating again.
Forty-four horses were enrolled in the trial, with approximately half receiving a placebo or "sham" treatment. Neither the owners nor the veterinarians administering the treatments knew which group their horses were in. As well as acupuncture, treated horses received Chinese herbal medicine. The placebo group received false acupuncture and hay powder.
The treated horses improved measurably after a month of acupuncture and herbal medicine. However, a significant portion of the placebo group also began sweating again during the trial. The trial horses had all recently become non-sweaters, and anhidrosis is known to spontaneously improve in some cases. The study's authors concluded that more research was required to understand the role of acupuncture in treating equine anhidrosis.
If you have questions about anhidrosis or acupuncture treatments, talk to you veterinarian.
Sources:
Machtinger, Erika T.; Leppla, Norman C.; and Saunders, Cindy. “Pest Management Perceptions and Practices for Equine Farms in North and Central Florida.” University of Florida College of Veterinary Medicine
University of California, Davis, School of Veterinary Medicine
Sykes, Melissa. “No Sweat.” The Horsemen's Journal