✓Reviewed by Ann Pruitt, InfoHorse.com·Updated May 2026
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Anhidrosis Prevention By ONE AC Help prevent the symptoms of Anhidrosis with One AC!
What Is Anhidrosis?
Anhidrosis-the partial or total inability to sweat-has been recognized in horses since the early 1920s. No definite reason has been discovered as to why some horses develop the problem, which can affect all ages and breeds. Anhidrosis is most commonly seen in horses living in America's Gulf Coast states, including Florida and Louisiana, and in South Texas.
What Causes Anhidrosis?
The ability to sweat is an essential physiological response in your horse if it is to perform in hot and humid climates. This ability to sweat allows your animal to maintain their interior core temperature at such a point so as not to interfere with their enzyme driven metabolic processes, which are also of an essential nature. Anhidrosis is a result of excess stress. By adding the additional stress of high temperature and humidity to an already stressful environment of training, some animals just can not produce sufficient dopamine to satisfy its needs. When this imbalance occurs, your horse begins to suffer the debilitating effects Anhidrosis.
What Is One AC And How Can It Help Prevent Anhidrosis?
One AC is a supplement based on the theory of imbalance of dopamine to the nor-adrenaline/adrenaline complex. Dopamine is used first by the brain, then by the cardiovascular system and last by the sweating system. A reduction in dopamine below a certain level allows the well-known vasoconstrictive properties of the nor-adrenaline/adrenaline complex to predominate and reduce the blood carrying capacity of the peripheral vascular system to a minimum, thereby reducing the ability of the sweat glands to function properly.
What Sets One AC Apart From Other Anhdrosis Treatments?
It works! It was field tested at Florida State University in Gainesville in early 1994. All the horses in the test program responded well to the One AC. There were no ill effects on the pregnant mares and healthy foals were delivered. One AC was developed specifically to help the non-sweater thermo regulate. Non-sweating is caused by the shutdown of the peripheral vascular system caused by nor-adrenaline and adrenalin (flight or fight syndrome). Portions of the metabolate are used by the thyroid gland to produce T-4 and T-3. Horses with anhidrosis test hypo-thyroid.
Does One AC Have Any Side Effects And How Do I Use It?
One AC is a natural product and there are no side effects to contend with. It can be used indefinitely during the hot humid weather, which brings on anhidrosis. It is recommended to feed One AC twice a day as it is a food. Depending on the extent to which the horse is involved with the anhidrosis, some folks will feed only once a day or every other day during the cooler months as a way to "keep the pump primed".
What Do Customers Say About One AC?
Thanks again for this wonderful product! It really, really works great!
Dana Hopkins
Thank you so much, the powder is s true lifesaver for my thoroughbred boy!
Carey Sweet
I have used One A C for two years and it works so well. I tried to stop using it one summer and my horse was suffering. He was so hot and puffing that I went back on the product and my horse was like a new horse. Great product! Thank you.
Linda Howell
Order One AC Today!
Don’t let your horse suffer the debilitating effects of Anhidrosis, visit us or find us at SmartPakEquine, ValleyVet, DoverSaddlery, JeffersEquine-- or your local tack store Today!
ONE AC anhidrosis powder supplement for horses by Mpco, stacked product jars
What Makes a Horse Stop Sweating?
When a horse loses the ability to sweat normally, the condition is called anhidrosis, or "dry coat." Because sweating is a horse's primary way to shed heat, an anhidrotic horse can overheat dangerously even during light work, breathing hard, flagging in performance, and struggling to cool down. ONE AC was developed specifically as a nutritional feed supplement to help non-sweating horses restore normal sweating function. According to Mpco, ONE AC has proven effective in controlling the negative effects of non-sweating in a large majority of cases.
Who Makes ONE AC
ONE AC is manufactured by Mpco and sold through its dedicated site at nonsweater.com. The formula was developed by biochemist Raymond LeRoy, who built it around the role of dopamine in regulating the equine sweating system. To order directly or check availability, customers can reach Mpco by, use the secure 24/7 online shopping cart, or consult the distributor list on the company's website to find a local retailer.
The Active Ingredients Inside the Jar
ONE AC is built around L-Tyrosine, niacin, and ascorbic acid (vitamin C), supported by Vitamin B6, Choline, and d-Pantothenic Acid. L-Tyrosine is the amino-acid precursor the body uses to manufacture dopamine and the catecholamine complex. One scoop equals 2.35 grams, and the formula was validated through field tests at the University of Florida.
How ONE AC Restores Normal Sweating
Developer Raymond LeRoy explains that the body spends its available dopamine first on the brain, second on the cardiovascular system, and last on the sweating system, so when dopamine runs low, sweating is the first function sacrificed. ONE AC supplies the raw nutritional materials the horse needs to rebuild dopamine production, allowing the β2-adrenergic sweat-gland receptors to resensitize and function again. Most horses begin sweating again within 10 to 14 days. For best results, strenuous training should be reduced or paused for roughly three weeks at the start of treatment, since premature hard work re-depletes dopamine and can reverse progress.
Which Horses Benefit Most
Anhidrosis can affect horses of all ages and breeds and is seen most often in hot, humid climates, so ONE AC suits performance, pleasure, and pasture horses living in those conditions. It works best in moderately affected horses and when supplementation begins before the onset of the hot season rather than after a horse has fully shut down. ONE AC has no known side effects, making it a practical daily addition to a feeding program.
Dosing and How to Order
For an average horse of 950 to 1,100 lbs, the recommended dose is one scoop twice daily, morning and evening. Horses 600 to 900 lbs take 1½ scoops daily, 300 to 600 lbs take 1 scoop per day, and miniature horses take ½ scoop per day; for horses over 1,100 lbs, add ½ scoop daily for each additional 100 lbs. Order through Mpco at nonsweater.com or by, and always consult your veterinarian before adding any supplement to your horse's program.
What is anhidrosis, and which horses are most at risk?
Anhidrosis is the partial or total inability to sweat. It's been recognized in horses since the early 1920s and can affect all ages and breeds. Horses living in America's Gulf Coast states — including Florida, Louisiana, and South Texas — are most commonly affected, because the combination of high heat and humidity puts the highest demand on a horse's sweating system.
What causes anhidrosis in the first place?
Sweating is how a horse maintains its core body temperature so the heat-sensitive enzymes that drive its metabolism can keep working. Anhidrosis is described as a result of excess stress: when a horse already in a stressful training environment is asked to work in high temperature and humidity on top, some animals can't produce enough dopamine to keep the sweat-gland system supplied. When that imbalance occurs, the horse begins to show the debilitating effects of anhidrosis.
What is One AC, and how is it designed to help?
One AC is a supplement built around the theory that anhidrosis comes from a dopamine imbalance against the nor-adrenaline / adrenaline complex. Dopamine gets used first by the brain, then by the cardiovascular system, and last by the sweating system. When dopamine drops below a certain level, the vasoconstrictive properties of the nor-adrenaline / adrenaline complex take over and reduce blood flow through the peripheral vascular system — which is what cuts off the sweat glands' ability to function. One AC is formulated to address that imbalance.
When would I consider One AC for my horse?
Consider One AC if you keep a horse in a hot, humid climate — especially in Gulf Coast states or South Texas — and you're seeing signs your horse isn't sweating normally during work or turnout. Anhidrosis affects all ages and breeds, so a horse that handled the heat fine in prior seasons can develop the problem too. The product is designed for prevention as well as response, so it's worth considering as part of a hot-weather management plan, not only after the symptoms get severe.
Has One AC been tested in the field?
One AC was field-tested at Florida State University in Gainesville in early 1994. Per the manufacturer's account of that program, all the horses in the test responded well to One AC.
How do I get One AC, or learn more before deciding?
Reach out to Anhidrosis Prevention By ONE AC directly to talk through whether your horse is a fit and to order. The company's website is nonsweater.com, and the contact phone is on the listing. As with any supplement decision, it's worth a conversation with the company about your horse's specific situation before starting.
What is ONE AC?
ONE AC is a nutritional feed supplement made by MPCO and developed specifically for horses suffering from anhidrosis, the partial or total inability to sweat. It is fed daily as a powder mixed into the horse's feed to help restore normal sweating function. MPCO reports it has been effective in controlling the effects of non-sweating in a large majority of cases.
What is anhidrosis in horses?
Anhidrosis is the partial or total inability to sweat, sometimes called dry coat. It has been recognized in horses since the early 1920s and can affect all ages and breeds. Because sweating is how a horse sheds excess body heat, an anhidrotic horse can overheat quickly and struggle to perform or even stay comfortable in hot weather.
What causes a horse to stop sweating?
No single definitive cause has been established, but anhidrosis is most commonly seen in horses living in hot, humid climates. ONE AC's developer, biochemist Raymond LeRoy, attributes the breakdown to dopamine depletion: when a horse's available dopamine runs low, the sweating system is the first function the body sacrifices. The sweat glands' β2-adrenergic receptors become desensitized after chronic overstimulation, and sweating shuts down.
What are the active ingredients in ONE AC?
ONE AC's key active ingredients are L-Tyrosine, niacin, and ascorbic acid (vitamin C), supported by Vitamin B6, Choline, and d-Pantothenic Acid. L-Tyrosine is the amino acid the body uses as a precursor to build dopamine and the catecholamine complex. These nutrients supply the raw materials the horse needs to restore dopamine production.
How does ONE AC work?
According to developer Raymond LeRoy, the body uses its available dopamine first for the brain, second for the cardiovascular system, and third for the sweating system. When dopamine becomes depleted, sweating is sacrificed first. ONE AC provides the nutritional building blocks to rebuild dopamine production, which allows the sweat glands' β2-adrenergic receptors to resensitize and resume normal function.
How is ONE AC dosed?
For an average horse of 950 to 1,100 lbs, the recommended dose is one scoop twice daily, in the morning and evening. Horses 600 to 900 lbs take 1½ scoops daily, horses 300 to 600 lbs take one scoop per day, and miniature horses take ½ scoop per day. For horses over 1,100 lbs, add ½ scoop daily for each additional 100 lbs of body weight.
How big is one scoop of ONE AC?
One scoop of ONE AC equals 2.35 grams. The included scoop makes daily measuring straightforward, and dosing is adjusted up or down based on the horse's body weight as described on the product label and the nonsweater.com product page.
How long does ONE AC take to work?
Most horses begin sweating again within 10 to 14 days of starting ONE AC. Results tend to be best in moderately affected horses and when supplementation is started before the onset of the hot season rather than after the horse has completely stopped sweating.
Does ONE AC have any side effects?
MPCO states that ONE AC has no known side effects, which makes it suitable as a daily addition to a horse's feeding program. As with any supplement, you should always consult your veterinarian before adding ONE AC to your horse's regimen.
Do I need to change my horse's workload when starting ONE AC?
Yes. The developer recommends reducing or pausing strenuous training for roughly three weeks when you begin treatment. Pushing an anhidrotic horse back into hard work too soon re-depletes dopamine and can reverse the progress ONE AC is helping to make, so a gradual return to work is important.
Is ONE AC backed by research?
ONE AC's formula has proven results from field tests conducted at the University of Florida. The product was developed by biochemist Raymond LeRoy around the dopamine-depletion mechanism of equine anhidrosis, and the science behind it is detailed on the company's website at nonsweater.com/thescience.
Which horses are most likely to benefit from ONE AC?
Anhidrosis affects horses of all ages and breeds, but it is most common in hot, humid climates, so horses living and working in those conditions are prime candidates. ONE AC works best in moderately affected horses and is most effective when started before the hot season begins, rather than after a horse has fully shut down its sweating.
Who makes ONE AC?
ONE AC is made by MPCO and sold through its website at nonsweater.com. The formula was developed by biochemist Raymond LeRoy. You can reach MPCO directly by phone at 602-866-7701.
How do I buy ONE AC?
ONE AC can be ordered directly from MPCO through the secure online shopping cart at nonsweater.com, which is available 24/7, or by calling 602-866-7701. The company also maintains a distributor list on its website so customers can find a local retailer that carries the product.
Can ONE AC be used on performance and show horses?
Yes. ONE AC is a nutritional feed supplement with no known side effects, making it appropriate for performance and pleasure horses alike. Because anhidrosis directly robs horses of the cooling they need to perform, restoring normal sweating helps competition horses work and recover in the heat. Always confirm compliance with your specific show or association rules and consult your veterinarian.
What is the difference between the product and the science behind it?
The nonsweater.com product page covers practical details like dosing by body weight and how to order, while the dedicated Science page explains the dopamine-depletion mechanism, the role of L-Tyrosine as a dopamine precursor, and how the β2-adrenergic sweat-gland receptors resensitize. Together they show both how to use ONE AC and why it works on the underlying cause of anhidrosis.
Should I talk to my veterinarian before using ONE AC?
Yes. MPCO advises that you should always consult with your veterinarian before administering any supplement to your horse, including ONE AC. Your vet can confirm that anhidrosis is the issue, rule out other causes of poor sweating or heat intolerance, and help you fit ONE AC into an overall heat-management and feeding plan.
