SmartPakEquine, ValleyVet, DoverSaddlery, JeffersEquine

Anhidrosis-the partial or total inability to sweat-has been recognized in horses since the early

Got a horse who's stopped sweating in the Gulf-state heat?

InfoHorseTV Facebook 📰 Articles 🧰 Tools

Reviewed by Ann Pruitt, InfoHorse.com · Updated May 2026

One AC Powder 200 gm jar anhidrosis supplement for non-sweating horses by MPCO

SmartPakEquine, ValleyVet, DoverSaddlery, JeffersEquine

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?

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 Customers Say

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 AC 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!

What exactly is anhidrosis, and why does it sideline a horse?
Anhidrosis is the partial or total inability to sweat, sometimes called "dry coat" or simply "non-sweating." Because a horse relies almost entirely on sweat to shed body heat, an anhidrotic horse loses its primary cooling system, so it overheats, breathes hard to dump heat through the lungs, tires quickly, and can become genuinely heat-distressed in hot, humid weather. The condition has been recognized in horses since the early 1920s and can affect any age or breed, with no single confirmed cause. One AC was developed to address the underlying nutritional depletion rather than just the symptoms.

One AC anhidrosis powder supplement label showing ingredients and feeding directions

Who makes One AC, and what is the company behind it?
One AC is made by Mpco (the Magic Powder Company), and it is the only product the company makes. The formula was developed by chemist Raymond LeRoy of Phoenix, Arizona, who funded the work himself out of conviction that anhidrosis was a solvable nutritional problem. The company operates from 500 N. Estrella Pkwy, B2-474, and can be reached at (602) 866-7701 or, with ordering and a distributor list available at nonsweater.com.

What is in One AC, and what does each ingredient do?
One AC is a vitamin and amino-acid blend whose three primary working ingredients are L-tyrosine, niacin, and vitamin C (ascorbic acid), supported by vitamin B6, d-pantothenic acid, and choline. The guaranteed analysis lists L-Tyrosine at a minimum of 36%, niacin at 36,288 mg/lb, Vitamin B6 at 35,380 mg/lb, d-Pantothenic Acid at 66,225 mg/lb, and Choline at 145,152 mg/lb. L-tyrosine is the amino-acid precursor the body uses to build dopamine, which is the linchpin of how the product is designed to work.

How does One AC restore a horse's ability to sweat?

One AC is built on Raymond LeRoy's theory of an imbalance between dopamine and the noradrenaline/adrenaline complex. As the maker explains it, "the available dopamine is used first by the brain, second by the cardiovascular system, and third by the sweating system" — so when dopamine runs short, sweating is the first function the body sacrifices. By supplying the raw nutrients the horse needs to rebuild that depleted dopamine pathway, One AC aims to bring the sweating system back online. Horses generally start sweating again within ten to 14 days of starting the supplement.

How is One AC fed, and what should owners expect?
One AC is an easy-to-feed powder dosed by body weight using the enclosed scoop (one scoop equals 2.35 g). An average 950–1,100 lb horse gets one scoop twice daily (AM and PM); 600–900 lb horses get 1 1/2 scoops daily (3/4 AM, 3/4 PM); 300–600 lb horses get one scoop per day; minis get 1/2 scoop per day; and horses over 1,100 lbs add a half scoop for every 100 lbs above that. For best results, the maker advises reducing strenuous training and work to a minimum for about three weeks when first starting the supplement.

Is One AC proven and safe, and where can you buy it?
One AC has proven results from field tests at the University of Florida, and practitioners report real-world success across a meaningful share of treated horses. The maker reports no side effects, states that no animal has tested positive on drug testing during use, and notes the supplement is safe for pregnant and lactating mares — though you should always consult your veterinarian before adding any supplement. One AC is sold direct at nonsweater.com and through national equine retailers including SmartPak Equine, Valley Vet, Dover Saddlery, Jeffers, Chewy, PBS Animal Health, and Santa Cruz Animal Health.

Share This Solution

Facebook X LinkedIn Email

The Solution Section (FAQ)

What Sets One AC Apart From Other Anhdrosis Treatments?

Does One AC Have Any Side Effects And How Do I Use It?

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 is One AC used for?

One AC is a nutritional feed supplement developed specifically to help prevent the symptoms of anhidrosis, the partial or total inability to sweat in horses. By supplying the raw nutrients the horse needs to rebuild a depleted dopamine pathway, it is designed to help non-sweating horses begin sweating normally again so they can cool themselves properly in hot, humid weather.

What is anhidrosis in horses?

Anhidrosis is the partial or total inability to sweat, also called 'dry coat' or 'non-sweating.' It has been recognized in horses since the early 1920s and can affect all ages and breeds. Because horses depend on sweating as their main way to release body heat, an anhidrotic horse overheats easily, breathes rapidly to shed heat through the lungs, and tires quickly during exercise or hot weather.

Who makes One AC?

One AC is made by MPCO, the Magic Powder Company, and it is the only product the company makes. The formula was developed by Raymond LeRoy, a chemist from Phoenix, Arizona, who funded the development himself. The company can be reached at (602) 866-7701 or [email protected], and sells online at nonsweater.com.

How does One AC work?

One AC is based on Raymond LeRoy's theory of an imbalance between dopamine and the noradrenaline/adrenaline complex. The available dopamine is used first by the brain, second by the cardiovascular system, and third by the sweating system, so when dopamine runs short the body sacrifices sweating first. One AC supplies the raw materials the horse needs to compensate for that depletion so the sweating function can return.

What are the ingredients in One AC?

The three primary working ingredients are L-tyrosine, niacin, and vitamin C (ascorbic acid), supported by vitamin B6, d-pantothenic acid, and choline. L-tyrosine is the amino acid the body uses to build dopamine, which is central to how the supplement is designed to function. The guaranteed analysis lists L-Tyrosine at a minimum of 36%, plus measured amounts of niacin, Vitamin B6, d-Pantothenic Acid, and Choline per pound.

How long does One AC take to work?

According to the maker, horses generally start sweating again within ten to 14 days of starting on One AC. Results can vary by horse, and for the best outcome the company recommends keeping strenuous training and work to a minimum for about three weeks when the supplement is first introduced.

How do you feed One AC to a horse?

One AC is an easy-to-feed powder dosed by body weight with the enclosed scoop, where one scoop equals 2.35 grams. An average 950 to 1,100 lb horse receives one scoop twice daily, morning and evening. Smaller horses and ponies receive less, and horses over 1,100 lbs add a half scoop for every 100 lbs above that weight.

What is the correct One AC dose by horse weight?

Miniature horses get 1/2 scoop per day; 300 to 600 lb horses get one scoop per day; 600 to 900 lb horses get 1 1/2 scoops daily split 3/4 AM and 3/4 PM; and average 950 to 1,100 lb horses get one scoop twice daily. For horses over 1,100 lbs, add a half scoop daily for each 100 lbs above the maximum weight.

Is One AC safe for pregnant or lactating mares?

The maker states that One AC is safe for pregnant and lactating mares and that no side effects have been reported. As with any supplement, you should always consult your veterinarian before adding One AC to your horse's program, especially for breeding stock or horses with existing health conditions.

Will One AC cause a positive drug test?

According to MPCO, no animal has tested positive during use of One AC. The supplement is a vitamin and amino-acid blend rather than a drug, which is consistent with that record. Owners competing under specific governing-body rules should still verify the product against their organization's current guidelines.

Has One AC been tested scientifically?

Yes. One AC has proven results from field tests conducted at the University of Florida. In addition, equine practitioners have reported real-world success in a meaningful share of the anhidrotic horses they have treated with the supplement.

Should I reduce my horse's work while starting One AC?

Yes. For best results, the maker advises reducing strenuous training and work to a minimum for about three weeks when first starting the supplement. This gives the horse's system time to rebalance and restore the sweating response before returning to a full workload.

What sizes does One AC come in?

One AC is sold in jar sizes such as a 200 gm container and a 7 oz jar, commonly described in day-supply terms based on the weight-based feeding chart. Larger and smaller supplies may be available depending on the retailer, so check the specific listing for the size and day count that fits your horse's dose.

Where can I buy One AC?

One AC is available direct from the maker at nonsweater.com, where there is also a distributor list for local availability. It is also carried by major equine retailers including SmartPak Equine, Valley Vet, Dover Saddlery, Jeffers, Chewy, PBS Animal Health, and Santa Cruz Animal Health.

How is One AC rated by horse owners?

On major retail platforms One AC has earned strong ratings, including a 4.5 out of 5 average from over 220 reviewers on SmartPak Equine. Reviews note that results can vary by horse, with many owners reporting that a non-sweating horse began sweating again within roughly ten days, while a minority report little change.

Why do horses stop sweating in the first place?

No single definitive cause of anhidrosis has been identified, which is part of what makes it so frustrating for owners. It can develop in any age or breed and is most common in hot, humid climates, and One AC's underlying theory is that the sweating system shuts down when the horse's dopamine supply is depleted and prioritized for the brain and cardiovascular system instead.

How do I contact One AC or the Magic Powder Company?

You can reach MPCO, the Magic Powder Company, by phone at (602) 866-7701 or by email at [email protected]. The company is located at 500 N. Estrella Pkwy, B2-474, and ordering plus a full distributor list are available online at nonsweater.com.