Alexia Austen Wishart answers:
Nosebleeds can be caused by many different and unrelated disease processes. For example, in the upper airways, they may involve structures of the nostrils, nasal passage, ethmoid turbinates (scroll-shaped bones at the back of the nasal passage) or sinuses. In the lower respiratory system, the most common cause is exerciseinduced pulmonary haemorrhage – also known as lower-airway bleeding when exercised. More rarely, nosebleeds may indicate issues with blood clotting.
To identify the source, your vet will check if the blood can be seen from one nostril or both. If bleeding is only from one nostril, then it’s more likely to be an upper respiratory issue, whereas if in both nostrils, it’s more likely to be of lower respiratory origin.