Exercise-Induced Pulmonary Haemorrhage
Learn what the condition is, how it may be detected early, how it is treated or managed, and which breeds or species are linked to it.
Condition snapshot
A concise guide to the condition’s pattern, detection, management and urgency.
This snapshot is a general guide, not a diagnosis or treatment plan. New, severe or worsening signs require veterinary assessment.
About the condition
Exercise-induced pulmonary haemorrhage, or EIPH, is bleeding into the lungs and airways during strenuous exercise. It is common in racehorses and also occurs in polo, eventing, barrel racing and other high-intensity disciplines. Extreme pulmonary vascular pressures during maximal work are thought to rupture fragile capillaries, particularly in the caudodorsal lung. Repeated episodes can produce inflammation, iron deposition, vascular remodelling and fibrosis.
Only a small minority of affected horses bleed visibly from the nostrils. Most have no obvious external sign; some show reduced performance, coughing, prolonged recovery or swallowing immediately after exercise. Because poor performance is nonspecific and visible epistaxis is uncommon, neither observation alone establishes severity. Profuse bleeding at rest is not typical and demands investigation for guttural-pouch mycosis, ethmoid haematoma, trauma or another source.
The probability and grade of EIPH tend to increase with age and cumulative high-speed starts. Exercise intensity, cold conditions and individual susceptibility can contribute. Mild blood detected after very strenuous work does not necessarily explain every performance problem, while recurrent high-grade haemorrhage can impair welfare and respiratory function.
EIPH is not contagious and does not require isolation. It also is not a clotting disorder in most horses, so unproven procoagulants or vitamin supplementation are inappropriate. The condition often recurs because available measures reduce severity rather than removing the exercise-related vascular forces. Management must balance diagnostic evidence, athletic goals, medication rules and the horse’s long-term respiratory health.
High pulmonary vascular pressures during maximal work allow capillaries to fail, most often in the caudodorsal lung. Blood may never reach the nostrils, so absence of visible epistaxis does not exclude EIPH. Repeated episodes can leave haemosiderin, inflammation and fibrosis, but poor performance has many causes and endoscopic blood must be interpreted in context.
Screening & Early Detection
Tracheobronchoscopy performed about 30 to 120 minutes after the relevant exercise is the standard direct assessment. Blood within the trachea is graded, and the upper airway is examined for an alternative source. Evidence may remain visible for one to three days, but timing and repeated examinations influence detection because bleeding severity varies between bouts.
Bronchoalveolar lavage cytology is useful when immediate post-exercise endoscopy was not possible. Red cells and haemosiderin-laden macrophages support recent or repeated pulmonary bleeding; iron-specific staining can improve identification. These cells can persist for weeks, so results do not precisely date one episode. Thoracic radiographs may show chronic caudodorsal change, but routine imaging is not sensitive for grading EIPH.
Poor performance evaluation should also assess asthma, upper-airway obstruction, cardiac disease, pain and training factors. A single low endoscopic grade does not exclude more severe bleeding on another day. Conversely, cytological evidence of old haemorrhage should not be assumed to explain current performance without correlation to exercise history and other findings.
Treatment & Management
There is no curative treatment for EIPH. Furosemide administered before strenuous exercise reduces the frequency and severity of bleeding in many racehorses, but does not eliminate it. Its use is tightly controlled or prohibited in many racing and sport jurisdictions, including rules that may differ by location and competition. Medication must therefore be prescribed by a veterinarian and checked against current governing-body requirements.
Evidence for nasal dilator strips is limited, and evidence supporting vitamin K, oestrogens, aminocaproic acid, bronchodilators, pentoxifylline or common supplements is weak. Treating documented concurrent asthma or upper-airway obstruction is appropriate for those disorders but should not be presented as a proven cure for EIPH. Rest allows recovery from an acute high-grade bleed, although prolonged rest alone has not been shown to prevent recurrence once intense work resumes.
Management includes reviewing training load, recovery, track surface, respiratory health and the horse’s cumulative bleeding pattern. Repeated high-grade haemorrhage or epistaxis warrants welfare-based reconsideration of competition intensity and further evaluation for another bleeding source. Horses with respiratory distress, collapse or heavy nasal bleeding after work need urgent care. Prognosis for continued exercise is variable: many horses compete with low-grade EIPH, while recurrent severe episodes may cause lasting pulmonary change and unacceptable risk.
Breeds or species affected
Anglo-Arabian
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Arabian
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Thoroughbred
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American Quarter Horse
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American Paint Horse
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Appaloosa
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Australian Stock Horse
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Standardbred
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Orlov Trotter
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