Exercise-Induced Pulmonary Haemorrhage in Horses

Exercise-induced pulmonary haemorrhage (EIPH) affects a large proportion of racehorses and other performance horses, causing bleeding in the lungs during intense exercise.

Key Facts

EIPH occurs when intense exercise causes blood to leak from capillaries into the airways of the lung.
Up to 75% of thoroughbred racehorses show evidence of EIPH when examined by endoscopy after racing.
Epistaxis (bleeding from the nose) is the visible symptom of severe EIPH, affecting approximately 1% of racing starts.
The diuretic furosemide (Lasix) is widely used in the US to reduce EIPH but is banned in many other countries on welfare and integrity grounds.
EIPH is associated with reduced exercise performance, coughing, and long-term lung damage in severely affected horses.
Resting, reduced training intensity, and nasal strips are non-pharmacological management strategies with variable evidence.
The condition worsens with repeated episodes, suggesting cumulative lung damage.
There is ongoing debate about whether horses with severe recurrent EIPH should be withdrawn from competition.

Welfare Considerations

EIPH raises difficult welfare questions at the intersection of equine health, athletic performance, and commercial pressure. A horse experiencing severe EIPH during a race is suffering significant physiological distress, yet the high prevalence of mild EIPH means that withdrawal from racing of all affected horses is impractical. The use of furosemide as a preventive treatment is controversial: while it reduces EIPH severity, it also masks the natural limitation that severe EIPH might impose, potentially allowing horses to compete at intensities their lungs cannot safely sustain. Welfare-centred racing governance should include clear thresholds for EIPH severity that trigger mandatory rest periods, and should evaluate horses individually rather than permitting blanket pharmacological management.

What You Can Do

Support racing regulatory bodies that take a welfare-based approach to EIPH management.
Advocate for clear rules on when horses with EIPH must be rested or retired from competition.
Encourage transparency in EIPH endoscopy data across racing industries.
Support research into the long-term respiratory effects of EIPH on horses.
Consider the welfare implications of the racing industry when engaging with equestrian sport.
Support organisations that provide retirement care for horses with chronic EIPH.