Horse Not Sweating: Anhidrosis Signs, Risks & What to Do

Anhidrosis means your horse is not producing enough sweat to cool the body normally. It is most often recognized in hot, humid climates and in horses that work or live in those conditions for long periods. Horses rely heavily on sweating for heat control, so even partial loss of sweating can lead to heat intolerance, heavy breathing, and poor performance.

The exact cause is not fully settled, but current evidence suggests the sweat glands become less responsive after ongoing stimulation in hot conditions. Some horses stop sweating completely, while others still sweat a little in limited areas such as under the mane, under tack, or around the perineum. Horses that move from cooler regions into hot, humid areas may be at higher risk.

Not every dry horse has primary anhidrosis. A horse may appear not to sweat because exercise intensity is low, the coat is clipped short and sweat evaporates quickly, or the horse is already dangerously dehydrated or overheated. Your vet may also consider other problems that can mimic or complicate anhidrosis, including respiratory disease, poor fitness, heat stress, and occasionally endocrine or metabolic issues.

Chronic cases may also develop dry or flaky skin, patchy hair loss, reduced thirst, and ongoing exercise intolerance. Because the main danger is failure to cool, the pattern matters as much as the symptom itself: a horse staying dry while breathing hard in summer heat is more concerning than a horse that is dry at rest on a mild day.

See your vet immediately if your horse is not sweating and has rapid or labored breathing, weakness, stumbling, depression, collapse, or a rectal temperature above 103°F. A temperature above 105°F is an emergency. These signs can mean the horse is overheating and needs prompt medical help. If your horse has colic signs, muscle stiffness, or cannot recover after exercise, that also moves this out of the "watch and wait" category.

You can monitor briefly at home if your horse seems bright, is comfortable at rest, and you only noticed reduced sweating during mild work or on a moderately warm day. Even then, stop exercise, move to shade, offer water, and watch breathing and temperature closely. If the pattern repeats, schedule a veterinary visit rather than assuming it will pass.

Hot, humid weather raises the risk. The Merck comfort index notes that when temperature plus relative humidity rises above 150, horses may not be able to cool themselves adequately through sweating. That matters even more for a horse already suspected of anhidrosis.

A good rule for pet parents: if your horse is dry when other horses are sweating, breathing harder than expected, or taking much longer than usual to cool out, call your vet the same day. Early management can help prevent heat injury and may reduce the need for emergency care.

Your vet will start with a physical exam, rectal temperature, heart rate, respiratory rate, hydration check, and a careful history. Expect questions about climate, travel, exercise level, how long the problem has been happening, whether your horse sweats in any body areas, and how quickly your horse recovers after work. This history is often very helpful because many horses with anhidrosis show a clear pattern of heat intolerance.

If your horse is currently overheated, treatment comes first. Your vet may recommend aggressive cooling, fluids, and monitoring until temperature and breathing improve. In more stable cases, the next step is confirming whether this is true anhidrosis or another issue causing poor heat tolerance.

Diagnostic testing may include bloodwork to assess hydration and electrolyte status and to look for other contributing problems. Some vets also use an intradermal sweat test, often with terbutaline, to measure whether the sweat glands respond normally. This test is especially useful when the diagnosis is unclear or when your vet wants to document severity.

After that, your vet will discuss management options. These may include exercise changes, environmental cooling, electrolyte support, and in selected cases a trial of supplements or other therapies. Response is variable, so treatment is usually about reducing heat risk and improving comfort rather than promising a cure.

Home care focuses on preventing overheating. Keep your horse in shade during the hottest part of the day, improve airflow with fans when safe, and schedule exercise for the coolest hours. If your horse starts breathing hard without sweating, stop work immediately and begin active cooling with cool water, scraping, and repeat applications until your horse is more comfortable. Offer fresh water often.

Track patterns. Write down the weather, workload, breathing rate, rectal temperature if you can take it safely, and whether your horse sweated at all. This gives your vet useful information and helps you spot worsening heat intolerance early.

Many horses with anhidrosis do best with reduced summer workloads. Some need turnout overnight instead of midday, lighter tack time, or a break from intense training. If your vet recommends electrolytes or dietary adjustments, follow that plan closely. Do not start supplements, beer, iodine products, or medications on your own, because evidence is mixed and some options are not appropriate for every horse.

If your horse lives in a persistently hot, humid region and continues to struggle despite careful management, ask your vet whether a temporary move to a cooler climate is realistic. For some horses, that is the most effective way to improve comfort and reduce risk.