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You also might be observing
Observation
What you see. The starting point for addressing any equine health related issue is your observation.
YOU ARE OBSERVING
Sweating, Anywhere on Body in Local Areas or Patches
Summary
SUMMARY
Equine sweat glands are prevented from producing sweat by a functioning nerve supply to the skin. If that nerve supply is lost or damaged for any reason, a local area of skin may produce sweat even when the horse has not recently exercised and the weather is not particularly hot. Horses that have injured a nerve may constantly sweat in the area of skin that is supplied by that nerve. The wet patch may be the only sign, or it may come with loss of hair, loss of feeling in the skin, or shrinking (atrophy) of the muscles nearby.
The location of the patch is the most useful clue, because it points to which nerve is affected and where along its path the damage is.
• Face, ear, and upper neck on one side, often with a drooping upper eyelid, a smaller pupil, or a sunken-looking eye on the same side: this pattern is called Horner's Syndrome. It results from damage to a nerve that runs from the chest up the neck to the head. Common causes include an injection that missed the jugular vein, trauma to the neck, and disease in the guttural pouch (an air-filled pouch at the back of the throat), which can be serious.
• A strip or patch on the neck, shoulder, or side of the body: usually damage to a spinal nerve from trauma (a kick, a fall, a collision, a halter or rope injury) or from an infectious disease of the nervous system such as EPM.
• A patch over a painful area: sometimes a horse sweats over a spot that hurts, such as a deep bruise, an abscess forming, or a strained muscle. In this case the sweating goes away as the pain resolves.
• Scattered patches in an older horse with a long or curly coat that sheds late: this can be one of the signs of a hormonal disorder of the pituitary gland (PPID, or Cushing's disease).
• A patch that sweats normally while the rest of the horse does not: the horse may have partial anhidrosis (reduced ability to sweat), and the "patch" is the only skin still working. This is a separate observation in this guide.
Sweating in patches is not usually an emergency by itself, but it should always be examined because it is a sign of a nerve problem, and some of the underlying causes are serious and time-sensitive.
Equine sweat glands are prevented from producing sweat by a functioning nerve supply to the skin. If that nerve supply is lost or damaged for any reason, a local area of skin may produce sweat even when the horse has not recently exercised and the weather is not particularly hot. Horses that have injured a nerve may constantly sweat in the area of skin that is supplied by that nerve. The wet patch may be the only sign, or it may come with loss of hair, loss of feeling in the skin, or shrinking (atrophy) of the muscles nearby.
The location of the patch is the most useful clue, because it points to which nerve is affected and where along its path the damage is.
• Face, ear, and upper neck on one side, often with a drooping upper eyelid, a smaller pupil, or a sunken-looking eye on the same side: this pattern is called Horner's Syndrome. It results from damage to a nerve that runs from the chest up the neck to the head. Common causes include an injection that missed the jugular vein, trauma to the neck, and disease in the guttural pouch (an air-filled pouch at the back of the throat), which can be serious.
• A strip or patch on the neck, shoulder, or side of the body: usually damage to a spinal nerve from trauma (a kick, a fall, a collision, a halter or rope injury) or from an infectious disease of the nervous system such as EPM.
• A patch over a painful area: sometimes a horse sweats over a spot that hurts, such as a deep bruise, an abscess forming, or a strained muscle. In this case the sweating goes away as the pain resolves.
• Scattered patches in an older horse with a long or curly coat that sheds late: this can be one of the signs of a hormonal disorder of the pituitary gland (PPID, or Cushing's disease).
• A patch that sweats normally while the rest of the horse does not: the horse may have partial anhidrosis (reduced ability to sweat), and the "patch" is the only skin still working. This is a separate observation in this guide.
Sweating in patches is not usually an emergency by itself, but it should always be examined because it is a sign of a nerve problem, and some of the underlying causes are serious and time-sensitive.
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Code Orange
Call Your Vet at Their First Available Office Hours- If you feel the problem is severe or has come on suddenly.
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Code Yellow
Contact Your Vet at Your Convenience for an Appointment- If the problem seems very mild and limited to a small area.
- If the results of the Whole Horse Exam (WHE) suggest the horse is otherwise normal.
your role
What To Do
• Assess the area for evidence of trauma or other abnormalities: wounds, scars, swelling, heat, hair loss, or a healed injury you had forgotten about. Compare the two sides of the horse.• Look for localized muscle atrophy (one muscle group smaller or flatter than the same muscle on the other side) or muscle trembling in or near the sweaty area. Stand behind and in front of the horse and compare left to right.
• Test skin sensation. Lightly touch or prick the sweaty area and the same area on the opposite side with a ballpoint pen cap and watch for a skin twitch. Reduced or absent response over the sweaty patch supports nerve damage. Note what you find.
• Look for lameness or an abnormal gait. Watch the horse walk and trot in a straight line and turn in tight circles both directions.
• If the patch is on the head or neck, look closely at the eyes. Compare the two upper eyelids, pupil sizes, and how deep-set each eye looks. Look for any nasal discharge or blood at the nostrils, and watch the horse eat and swallow.
• Consider the horse's history. Do you remember a traumatic injury near the wet spot? A kick, a fall, getting cast in the stall, getting caught in a fence or trailer? Has the horse had an injection in the neck recently, or been sedated by someone else? Has the horse traveled or been in contact with new horses?
• Note when the sweating started, whether it is constant or comes and goes, whether it is getting larger or smaller, and whether anything else has changed in the horse. Take dated photos with something for scale.
• Do a Whole Horse Exam (WHE) to look for other signs of illness.
• Share your findings and concerns with your vet.
What Not To Do
• Do not dismiss a patch of sweating as "just a quirk." It is a sign of a nerve problem until proven otherwise.• Do not ignore a sweaty patch on the head or neck that comes with a droopy eyelid, nasal discharge, or nosebleed. Guttural pouch disease can be life-threatening.
• Do not assume it is from a recent injection just because there was one. Tell your vet about the injection, but let them rule out other causes.
• Do not treat the skin with topical products expecting to stop the sweating. The problem is in the nerve, not the skin.
• Do not give bute or Banamine for days on end without your vet's involvement. It may hide a lameness or other sign your vet needs to see.
• Do not wait to see whether it resolves if there are any other neurologic signs (wobbliness, weakness, muscle shrinking, head tilt, difficulty swallowing).
Skills you may need
Procedures that you may need to perform on your horse.
your vet's role
• Your vet assesses general health, looking for an explanation for the sign. They particularly try to rule out neurologic causes for the sign.
• They map the sweaty area precisely and assess the skin carefully for loss of sensation, then use that map to work out which nerve is involved and where it is likely damaged.
• They perform a neurologic examination to determine whether the problem is limited to one nerve or involves the spinal cord or brain.
• Nerve damage can also occur from infectious diseases like EPM. In areas in which EPM is prevalent, your vet may consider EPM testing (blood and sometimes spinal fluid).
• For areas around the head that sweat, your vet considers ruling out Horner's Syndrome. This involves examining the eye and eyelid, reviewing recent injections and neck trauma, and often examining the guttural pouches with an endoscope, because guttural pouch disease can damage the nerve and may need urgent treatment.
• Depending on findings, your vet may recommend ultrasound of the neck or chest, radiographs of the neck, or other imaging to look for masses, injury, or infection along the path of the nerve.
• If PPID is suspected, your vet runs a hormone test (ACTH).
• If the cause is a simple nerve bruise from trauma, treatment is usually time and anti-inflammatories, and your vet will help you track whether the patch is shrinking over weeks to months. If the cause is infection, disease of the guttural pouch, or a mass, treatment is directed at that condition.
• They map the sweaty area precisely and assess the skin carefully for loss of sensation, then use that map to work out which nerve is involved and where it is likely damaged.
• They perform a neurologic examination to determine whether the problem is limited to one nerve or involves the spinal cord or brain.
• Nerve damage can also occur from infectious diseases like EPM. In areas in which EPM is prevalent, your vet may consider EPM testing (blood and sometimes spinal fluid).
• For areas around the head that sweat, your vet considers ruling out Horner's Syndrome. This involves examining the eye and eyelid, reviewing recent injections and neck trauma, and often examining the guttural pouches with an endoscope, because guttural pouch disease can damage the nerve and may need urgent treatment.
• Depending on findings, your vet may recommend ultrasound of the neck or chest, radiographs of the neck, or other imaging to look for masses, injury, or infection along the path of the nerve.
• If PPID is suspected, your vet runs a hormone test (ACTH).
• If the cause is a simple nerve bruise from trauma, treatment is usually time and anti-inflammatories, and your vet will help you track whether the patch is shrinking over weeks to months. If the cause is infection, disease of the guttural pouch, or a mass, treatment is directed at that condition.
Questions Your Vet Might Ask:
- Where exactly on the body is the sweating? Can you describe the borders or send a photo?
- Has the horse had an injection in the neck, or been sedated, in the last few weeks? Who gave it and where?
- Where has the horse lived?
- Do you recall an accident or injury in the horse's history?
- When did the horse last look normal?
- When did you first notice this?
- Do you notice an injury to the area?
- Do you notice areas of muscle loss anywhere else?
- Do you notice areas of muscle loss or atrophy anywhere near this area?
- Does the horse's appetite and attitude seem normal?
- What are the results of the Whole Horse Exam (WHE)?
Diagnostics Your Vet May Perform
Figuring out the cause of the problem. These are tests or procedures used by your vet to determine what’s wrong.
Very Common
Less Common
Diagnoses Your Vet May Consider
The cause of the problem. These are conditions or ailments that are the cause of the observations you make.
Very Common
Less Common
Rare
Treatments Your Vet May Recommend
A way to resolve the condition or diagnosis. Resolving the underlying cause or treating the signs of disease (symptomatic treatment)
Very Common
