Bit & Bridle

Equine Epistaxis (Nosebleeds)

Other Names

  • Epistaxis
  • Nosebleed
  • Exercise-induced pulmonary haemorrhage (EIPH) — when occurring after exercise

What is Equine Epistaxis?

Epistaxis — the medical term for a nosebleed — refers to bleeding from the nostrils in horses. It is not a disease in itself, but rather a clinical sign that can originate from a wide range of underlying causes affecting various regions of the respiratory tract, from the nasal passages and sinuses to the lungs. Identifying the origin and cause of the bleeding is essential for appropriate treatment and management.

Nosebleeds in horses can range from a few drops of blood-tinged nasal discharge to torrential haemorrhage that is immediately life-threatening. The character, timing, quantity, and sidedness (one nostril versus both) of the bleeding all provide important diagnostic clues. Blood from one nostril suggests a problem in the ipsilateral (same-side) nasal cavity, sinuses, or guttural pouch, while bleeding from both nostrils simultaneously suggests a pulmonary (lung) source.

Epistaxis following intense exercise — known as exercise-induced pulmonary haemorrhage (EIPH) — is the most commonly recognised form in performance horses, particularly racehorses. However, all equine nosebleeds warrant veterinary assessment to determine the cause.

Causes

The most clinically significant causes of equine epistaxis include:

  • Exercise-induced pulmonary haemorrhage (EIPH): Bleeding from pulmonary blood vessels during or after intense exercise, caused by the extremely high pulmonary blood pressures generated during galloping and racing. The blood originates in the lung and drains via the trachea to the nostrils. Studies using endoscopy suggest that EIPH affects a majority of intensely exercised horses to some degree, though only around 5% have blood visible at the nostrils. Risk factors include cold weather racing, a high number of lifetime race starts, and certain conformational traits.
  • Guttural pouch mycosis: Fungal infection of the guttural pouches (large air-filled cavities in the horse’s skull) can erode the walls of major blood vessels including the internal carotid artery. This can cause catastrophic, life-threatening haemorrhage — often recurring and potentially fatal. Guttural pouch mycosis must be excluded urgently in any horse with unexplained, recurrent, or severe unilateral epistaxis.
  • Progressive ethmoid haematoma (PEH): A non-cancerous, progressively enlarging mass that develops from the ethmoid region of the nasal cavity or sinuses. It causes intermittent, typically one-sided epistaxis — often a small amount of blood-tinged discharge rather than active bleeding. PEH can be treated with injection of formalin under endoscopic guidance.
  • Sinusitis: Inflammation or infection of the paranasal sinuses (often secondary to dental disease — see our entry on equine tooth abscesses) can cause blood-tinged nasal discharge, particularly if chronic and severe.
  • Trauma: Fractures of the facial bones or skull base caused by kicks, falls, or trailer accidents can produce significant epistaxis, particularly in young non-athletic horses.
  • Nasal polyps or tumours: Masses within the nasal cavity or sinuses can cause unilateral, intermittent blood-tinged discharge.
  • Clotting disorders: Rare conditions affecting the blood’s ability to clot — including thrombocytopaenia and certain toxicoses (e.g. sweet clover poisoning causing warfarin-like haemorrhage) — can cause epistaxis.
  • Idiopathic: In some cases, a definitive cause cannot be identified despite thorough investigation.

Symptoms and Signs

  • Blood from one nostril: Suggests a unilateral source in the nasal cavity, sinus, or guttural pouch on that side.
  • Blood from both nostrils: Suggests a pulmonary source (EIPH) or bilateral disease.
  • Timing: Blood appearing immediately after intense exercise strongly suggests EIPH. Blood at rest, or triggered by eating, raising the head, or palpating the sinuses, points to local nasal or sinus disease.
  • Character of discharge: Bright red blood indicates active haemorrhage. Old blood or dark, clotted material suggests a chronic process. Blood mixed with nasal secretions is common in sinusitis and PEH.
  • Recurrence: Repeated episodes of one-sided epistaxis are particularly concerning for guttural pouch mycosis or PEH.
  • Volume: Small, intermittent bleeding is less immediately dangerous than massive haemorrhage. A horse bleeding heavily from the nostrils at rest may have guttural pouch arterial haemorrhage — this is an emergency.

Diagnosis

  • Endoscopy: Upper airway endoscopy is the most valuable diagnostic tool. It allows direct visualisation of the nasal passages, nasopharynx, guttural pouches, and larynx and trachea. It can identify the site and source of bleeding, guttural pouch lesions, PEH, sinusitis, and pulmonary haemorrhage draining from the trachea following exercise.
  • Radiography: Skull radiographs can identify sinus disease, dental pathology, bone fractures, and masses.
  • Ultrasonography: Can assess soft tissue structures and fluid accumulation within sinuses.
  • CT scanning: Provides the most detailed imaging of the nasal cavity, sinuses, and guttural pouches at referral centres.
  • Haematology and clotting profile: Blood tests assess platelet count and clotting function in horses where a systemic clotting disorder is suspected.
  • Exercise endoscopy: Dynamic endoscopy performed on a treadmill or ridden on a track immediately post-exercise allows direct assessment of the airways during and after exertion, and is gold standard for EIPH diagnosis.

Treatment

Treatment is directed at the underlying cause:

  • EIPH: Furosemide (Lasix/Salix), a diuretic, is widely used in countries where its competition use is permitted (notably the USA) to reduce the severity of EIPH. It is banned on race days in many jurisdictions including the UK. Nasal strips that reduce upper airway resistance have some supporting evidence. Rest following an EIPH episode, and graduated return to exercise, are important management strategies.
  • Guttural pouch mycosis: Requires urgent referral to a specialist centre. Treatment involves endoscopic placement of occlusion coils or balloons within the affected blood vessels to prevent further haemorrhage, combined with antifungal therapy (e.g. itraconazole or voriconazole administered directly into the pouch). This is a serious condition requiring specialist intervention.
  • Progressive ethmoid haematoma: Repeated endoscopic injection of 10% formalin directly into the mass is the most common treatment. Surgical excision is an option for larger or poorly located masses. Recurrence is common regardless of treatment method.
  • Sinusitis: Treat the underlying cause (dental extraction if dental disease is present), combined with sinus flushing and systemic antibiotics.
  • Acute haemorrhage: Ice packs to the nasal region, keeping the horse calm and still, and urgent veterinary attention. Do not attempt to pack the nostrils of a horse — unlike in humans, this does not apply effective pressure to the source of equine nasal bleeding.

Prevention

  • Manage EIPH risk by avoiding overtraining young horses, building fitness gradually, and monitoring horses closely for post-exercise blood.
  • Schedule regular dental checks to prevent tooth root infections that progress to sinusitis.
  • Maintain annual respiratory endoscopy monitoring for horses that have previously bled post-exercise or shown unexplained respiratory discharge.
  • Inspect horses carefully after any head trauma — don’t assume that post-trauma blood will resolve without assessment.

Prognosis

Prognosis varies widely by cause. EIPH is generally manageable, and most affected racehorses continue to compete with appropriate management. PEH can be controlled with repeated treatment but rarely eliminated entirely. Guttural pouch mycosis carries a serious prognosis — the risk of fatal haemorrhage is significant — but outcomes have improved dramatically with modern endoscopic occlusion techniques, and survival rates of 60–90% are reported at specialist centres when treatment is performed before catastrophic haemorrhage occurs. Sinusitis and traumatic epistaxis generally carry a good prognosis with appropriate treatment.

When to Call the Vet

Any horse bleeding from the nose warrants veterinary assessment. Treat the following as emergencies requiring immediate contact: heavy, pulsatile, or uncontrolled bleeding from one nostril at rest; a horse that has had multiple separate bleeding episodes from one side; blood following head trauma. Do not wait to see if the bleeding stops — guttural pouch haemorrhage can be rapidly fatal. For related reading, see our guide on Equine Pulmonary Fibrosis and equine respiratory health. The British Equine Veterinary Association can help locate a specialist in equine respiratory medicine.

Frequently Asked Questions

Is it normal for racehorses to bleed from the nose?

Visible epistaxis after racing — so-called “bleeders” — is relatively common in racehorses worldwide. Research using endoscopy has shown that the majority of racehorses have some degree of EIPH, though visible blood at the nostrils occurs in only around 1–5% of race starts. It is managed rather than cured in most affected horses. However, any racehorse found to be bleeding at the nostrils after racing should be stood down and assessed by a veterinarian before returning to competition.

What is guttural pouch mycosis and why is it so dangerous?

The guttural pouches are large paired air-filled extensions of the Eustachian tubes located at the base of the horse’s skull, in close proximity to several major arteries including the internal carotid artery. Fungal infection (typically Aspergillus spp.) can erode the walls of these vessels, resulting in sudden massive haemorrhage. Because the blood vessels involved carry a large volume of blood at high pressure, affected horses can lose fatal volumes of blood very rapidly. Multiple haemorrhagic episodes are common — the first may appear to resolve, giving a false sense of security, but subsequent events can be fatal within minutes.

My horse had blood from one nostril after exercise — should I be worried?

A small amount of blood-tinged nasal discharge after intense exercise is relatively common in performance horses and most likely represents mild EIPH. However, a single episode does not allow you to rule out more serious causes such as PEH or guttural pouch disease. Your veterinarian should perform an endoscopic examination to determine the source. If the bleeding recurs, or if it occurred at rest rather than post-exercise, seek veterinary attention promptly.

Can young horses get nosebleeds?

Yes. Nosebleeds in young horses not in athletic training are more likely to be due to trauma (kicks, fence injuries, falls), structural abnormalities, or local nasal disease rather than EIPH, which develops with repeated high-intensity exercise. Any nosebleed in a non-athletic young horse should be investigated to identify the cause.