Anhidrosis in Horses

to be linked to overstimulation of the horses sweat glands by stress hormones often in the heat of the summer. Anhidrosis can be brought on by a plethora of triggers including electrolyte imbalance and overtraining2.
Antihistamines and macrolide antibiotic broadspectrum antibiotics used against many grampositive bacteria use can lead to temporary anhidrosis but the condition typically abates once the drug ceases to be administered.
The form of anhidrosis most horses experience is called chronic idiopathic anhidrosis CIA. CIA is frustrating for horse owners as it is the most difficult form to control. A treatment for complete resolution is not yet available but steps can be taken to make the horse more comfortable.
Researchers at the University of Florida Institute of Food and Agricultural Sciences UFIFAS have identified a genomic marker that contributes to CIA. The scientists discovered a genetic marker pointing to a defective potassium transporter channel3. The research team hypothesizes that sweat glands trying to use these damaged channels eventually lose their ability to sweat.
Diagnosis and Management of Anhidrosis
A horse is often diagnosed with anhidrosis by clinical observation and examination including a medical history. However a sweat test can be done to quantitatively assess how well the horse can sweat.
A sweat test involves a series of intradermal terbutaline injections which should increasingly stimulate the horses sweat glands as medication concentration rises. The vet will likely also run a blood panel that includes an electrolyte analysis this may assist in the formation of a treatment plan. A skin biopsy can also be performed but its rarely necessary to look at the skin microscopically to make a definitive diagnosis.
Once a horse is diagnosed with anhidrosis he must be given supportive care to assist with thermoregulation. Management changes are often necessary to ensure the horses safety as well. This doesnt often mean moving your horse

to a cooler climate although in extreme cases relocation may be considered.
Simple management modifications can include limiting sun exposure and minimizing turnout during the hottest time of day. Reducing training and showing schedules is often necessary but making sure the horse isnt ridden during the hottest part of the day may suffice and allow the horse to remain in work.
Supplements and Acupuncture
Many owners find themselves eager to try anything that could help their anhidrotic horse. You may have heard about adding a daily dark beer to his grain ration there is no harm in this though it hasnt been shown