Anhidrosis – when your horse doesn’t sweat!


  • Well, let’s start with what it is. Anhidrosis in horses is a failure to sweat. There is also hypohidrosis, which is the failure to sweat enough. I have also heard this be called partial anhidrosis.



  • Many a horse has collapsed and even died as a result of anhidrosis.


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We are all stumped as to the cause of anhidrosis in horses, but we do know what can help it – in some cases.


  • For the most part, experts, veterinarians, and researchers can agree on one thing – no one knows the reason for anhidrosis or the cure for it.


  • Generally speaking, it’s agreed that anhidrosis is some defect in the sweat glands. It’s widely assumed that the sweat gland becomes desensitized to the chemical trigger of epinephrine.


  • In this case, increased concentrations of epinephrine which normally signal the sweat gland to start working are ignored.

Any horse can develop anhidrosis at any time.


  • Age, gender, color, breed, and location don’t seem to be factors, although it’s reported that horses in hot and humid climates are likely to develop anhidrosis more often than more temperate climates.


  • It’s also known that horses can develop this overnight, or over time.


  • Anhidrosis can also resolve itself, without explanation or logical reason. Nice to have such concrete info, right? In a nutshell, we can’t yet predict it or cure it.


horse thermometer with attached string

You will need to monitor your horse’s temperature regularly.


How to manage anhidrosis in horses.


  • First, we need to discuss how to spot it – or even the beginnings of it. This is also where knowing your horse’s TPR comes into play – because, with diminished sweating, the internal temperature of your horse can reach over 104 degrees and cause heat stress and stroke.


  • Obviously, you will notice a horse with different or changing sweat patterns. For example, the hind legs and neck may sweat, while under the saddle does not. Or vice versa.


  • Or, you will notice no sweating at all. You will also notice lethargy, increased TPR values even at rest, dry itchy skin, hair loss (especially on the face) and increased recovery time after exercise.


It can resolve itself, sometimes.


  • Some horses are fine the next season, or they become adjusted to the climate.


  • Others are normal for years and years and then develop anhidrosis, even without climate change.


  • Some horses start to sweat again after a barn change in the same town.


Things to try


  • There are a ton of ideas out there for management, and if you do the research, you will find a lot of contradictory information.


  • As much as anhidrosis has no rhyme or reason, the treatments don’t have any rhyme or reason, either. What works for one horse doesn’t make a dent in others.


  • Most importantly, if you suspect anhidrosis, talk to your veterinarian and start monitoring that TPR right away.


  • There are a few tests your veterinarian can perform to confirm anhidrosis, one of them is a simple injection into the skin with epinephrine, which stimulates sweating. If your horse doesn’t sweat as a response to this, you are on the way to a diagnosis.


  • Many horse owners have had success with the supplement One A/C. Others can manage with electrolytes, beer, methyl dopa, thyroid supplements, and even acupuncture.


three beers for a flight at a brewery

Maybe your horse will share with you?


You will also need to monitor your horse’s environment and lifestyle.


  • Exercise in cooler parts of the day, which is often the morning. Early morning. Avoid turn out without ample shade and fresh water. Set up a fan if you can, although a misting system is better as the gentle mist utilizes evaporative cooling and takes the place of sweat.


  • You may also have some success with a diet change, reducing the protein and carbs and increasing fat as the energy source. This, and all management options, should be discussed with your Veterinarian.


  • During exercise, be sure to monitor respiration and take lots of walk breaks. Have a bucket with cold water and a sponge on the rail, or a spray bottle with water and rubbing alcohol close by.


  • Frequent dousing with the sponge, followed by the sweat scraper will help. If you use the spray with alcohol, you may not need to scrape as the alcohol evaporates so quickly. Hit under the neck and the major arteries of inside hind legs.


  • After the workout, implement major cooling-off techniques. Monitor your horse’s TPR closely, and check on him about 30 minutes later. By then, his vitals should be back to normal, and if not, call your Veterinarian and keep cooling off.


  • You can also consider some creative clipping to make some air conditioning for your horse. There is no reason not to clip the horse with anhidrosis in the summer. Help him any way you can!


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