Anhidrosis in Horses: When Your Horse Stops Sweating

By Dr Duncan Houston

A dry horse after exercise is not always a comfortable horse. If it is hot, breathing hard and sweating less than expected, impaired sweating needs to be considered.

Anhidrosis can be partial, so a damp patch beneath the saddle does not necessarily mean normal cooling. The horse’s breathing, temperature and recovery are more informative than coat appearance alone.

Quick Answer

Anhidrosis is reduced or absent sweating, which can limit a horse’s ability to lose heat. Stop exercise, move to shade and actively cool an overheated horse while contacting your vet. Long-term care relies on reducing heat exposure and adjusting workload; supplements and electrolyte products are not established universal cures.

Why does sweating matter?

Evaporation of sweat helps remove heat generated by work and the environment. High humidity reduces evaporation, making cooling harder even for normally sweating horses. A horse with impaired sweating has less capacity to cope.

The University of Florida’s anhidrosis guidance describes reduced sweating, poor performance and difficulty tolerating hot conditions. The cause is incompletely understood; it should not automatically be blamed on one dietary deficiency.

Some horses show patchy sweating or a reduced amount rather than none at all. Chronic cases may also have a dry coat and reduced exercise tolerance. New breathing difficulty must still be investigated for other causes.

How urgent is it?

What else could explain the signs?

Respiratory disease, pain, fever, dehydration and exhaustion can cause fast breathing or poor recovery. A horse may sweat less simply because the day or workload is different. Diagnosis depends on context and examination, not a single dry patch.

Your vet may review exercise and weather records and perform a controlled sweat-response test. Blood tests can assess associated problems, but a normal electrolyte result does not prove normal sweat-gland function.

When is this an emergency?

Overheating with altered behaviour, weakness, incoordination or collapse is an emergency. Call your vet and begin cooling immediately. Remove tack, use shade and airflow, and apply continuous cool or cold water over the body when safe.

Published equine cooling guidance supports continuous water application and cautions against interrupting effective cooling repeatedly to scrape. Do not force an exhausted horse to keep walking or delay cooling while trying to obtain a temperature.

If safe, record rectal temperature and changes in breathing for your vet. Provide drinking water to an alert horse able to swallow, but do not force oral fluids into a weak or uncoordinated horse.

A practical management plan

1. Record when sweating changed and the weather and workload involved.
2. Arrange an examination and review possible respiratory or systemic disease.
3. Provide shade, ventilation and reliable fresh water; assess the actual heat inside the stable.
4. Reduce or suspend work according to the vet’s plan. Cooler hours help only if conditions and the horse’s response are suitable.
5. Agree monitoring and emergency thresholds with everyone handling the horse.

For persistent cases, relocation to a cooler environment may be the most effective option. Improvement does not justify immediately resuming previous workloads. Reassess tolerance cautiously and keep a record of recovery after permitted activity.

Do supplements help?

Many products have been promoted, but convincing evidence of a consistent cure is lacking. Correct genuine dietary deficits and replace losses appropriately, while keeping plain water available. Do not give concentrated electrolyte pastes to a dehydrated horse without veterinary advice.

Ongoing University of Florida research illustrates that important questions about the condition remain unresolved. A testimonial does not establish that a product restores sweating safely.

Common mistakes

• Working harder to try to make the horse sweat.
• Assuming a little sweat means cooling is adequate.
• Relying on a supplement while heat exposure continues.
• Withholding water after exercise.
• Keeping a struggling horse moving instead of cooling it.

Reducing risk

Monitor heat and humidity, allow acclimatisation after moves, and match work to fitness. Provide rest, social contact and suitable low-demand activity when safe. An established anhidrosis diagnosis should be clearly communicated to carers and trainers before hot weather or travel.

Frequently asked questions

Can a horse have partial anhidrosis?

Yes. Sweating may be reduced or uneven.

Will electrolytes cure it?

Not reliably. They support appropriate fluid and mineral management but are not a proven cure.

Can my horse still be ridden?

Only within an individual veterinary plan and suitable environmental conditions.

Can it improve in cooler weather?

Some horses improve, but recurrence and residual limitations need monitoring.

Take abnormal heat recovery seriously. Protecting the horse from overheating is the immediate priority while the longer-term plan is developed.

For help understanding your horse’s care and preparing questions for your veterinarian, visit ASK A VET™. Urgent signs need an equine veterinarian in person.