SYMPTOM
Blood from the nose
Owners notice blood coming from one or both nostrils, which may appear as occasional spots, a persistent trickle, or blood mixed into sneezed discharge.
Local Trauma or Minor Vessel Injury
A bump to the nose, or vigorous scratching or pawing at the face, can rupture a small superficial blood vessel in the nasal lining. This produces a brief, usually one-sided bleed without other illness signs.
Foreign Material Lodged in the Nasal Passage
Grass seeds and other plant material can be drawn up into the nostril, especially in outdoor and field-active dogs during warmer months. They can become lodged and cause localised irritation, sneezing fits and intermittent one-sided bleeding until removed.
Nasal or Sinus Infection and Inflammation
Fungal rhinitis (in dogs usually Aspergillus fumigatus, most often in long-nosed breeds; in cats with aspergillosis, flat-faced breeds such as Persians are over-represented), along with bacterial secondary infection or chronic inflammatory rhinitis, can erode the nasal lining over time. This tends to produce recurring, often one-sided bleeding with nasal discharge and sneezing.
Dental Root Disease Extending into the Nasal Cavity
The roots of the upper canine and premolar teeth sit close to the nasal cavity floor. Longstanding periodontal infection can erode through this thin bone, particularly in small-breed dogs and older animals with dental disease, presenting as nasal bleeding.
Growth Within the Nasal Passage
Nasal tumours become more common with age in both species, though the typical type differs: in dogs these are most often carcinomas, including adenocarcinoma, while lymphoma is the more usual nasal tumour type in cats. Whatever the type, they tend to cause progressive, usually one-sided, recurrent bleeding, often together with reduced airflow through the affected nostril and facial changes as they enlarge over time.
Whole-Body Causes
Conditions that impair normal clotting, such as anticoagulant rodenticide exposure, lungworm (Angiostrongylus vasorum) infection in dogs, immune-mediated platelet destruction, or tick-borne infection, can present with nasal bleeding alongside bruising elsewhere. Uncommonly, high blood pressure in older cats can also rupture small nasal vessels directly.
Why timing matters
Early observation
A first, brief bleed straight after a witnessed knock to the nose fits a local, mechanical cause. With a minor injury of this kind there is typically no accompanying illness, and the bleeding usually stops within a few minutes. Without a witnessed injury, a brief bleed that stops by itself cannot be told apart at home from the first bleed of a nasal or whole-body disease.
Later presentation
Bleeding that recurs over days to weeks, especially if it becomes more frequent or is joined by nasal discharge, snoring-type noises, or visible facial swelling, points towards an underlying process within the nasal passage rather than a one-off injury. Bleeding accompanied by bruising elsewhere on the body shifts the pattern towards a whole-body explanation; bleeding from both nostrils leans the same way, though advanced nasal disease can also reach both sides. Equally, a clotting problem can bleed from one nostril only, so one-sided bleeding does not rule out a whole-body cause.
A scratch tends to resolve, and a lodged grass seed tends to cause intermittent episodes until it is removed. Erosive or growth-related causes tend to recur, often more frequently over time, usually starting from one nostril and sometimes spreading to both as they advance. Among local causes, the interval between episodes therefore helps separate a one-off injury from an erosive or growth-related process. How brief or light a bleed is does not separate local from whole-body causes: in a study of 176 dogs with nosebleeds, severity, and whether the bleeding was recent or longstanding, were similar in both groups. A clotting or platelet problem is identified by blood tests, not by the look of the bleed.
Conditions commonly associated
Aspergillosis (Nasal)
Fungal infection of the nasal passages can erode the nasal lining over time, producing recurring, often one-sided nasal bleeding together with sneezing and nasal discharge.
Anticoagulant Rodenticide Toxicity
Ingestion of anticoagulant rodenticide impairs the body's normal clotting mechanisms, and nosebleeds can be one of the first visible signs of a clotting failure that is often also causing hidden bleeding into the chest, lungs or abdomen, which can be life-threatening.
Periodontal Disease
Longstanding infection around the tooth roots, particularly the upper canines and premolars, can erode through the thin bone separating the mouth from the nasal cavity and present as nasal bleeding.
Systemic Hypertension in Cats
Elevated blood pressure, often linked to underlying kidney disease or an overactive thyroid in older cats, can occasionally cause small vessels within the nose to rupture spontaneously.
Chronic Upper Respiratory Disease in Cats
Ongoing viral or bacterial inflammation of the nasal passages in cats can damage the nasal lining over time, contributing to intermittent bleeding alongside sneezing and discharge.
Lymphoma in Dogs
Nasal lymphoma is one of the growths that can arise within the nasal cavity of older dogs, typically producing progressive, one-sided bleeding together with reduced airflow through the affected nostril.
Immune-Mediated Haemolytic Anaemia (IMHA)
This condition can occur alongside immune-mediated destruction of platelets, and the resulting drop in platelet numbers can contribute to spontaneous bleeding from mucosal surfaces including the nose.
The page on this condition is being checked again and is offline for now.
Nasopharyngeal Polyps
In cats, the growth can irritate and obstruct the nasopharynx, the airway behind the nose, and can occasionally cause inflammation and surface bleeding, which may appear as spots of blood or blood-tinged discharge from the nose. Sneezing and difficulty breathing through the nose often accompany the bleeding.
Vasculitis
Inflammation of small blood vessels in the nasal lining can cause those vessels to leak or rupture, producing bleeding that may appear as spots, crusting, or frank blood from the nostrils. The bleeding reflects the broader pattern of vessel damage that can affect multiple sites in the body.
Angiostrongylus (Lungworm)
Dogs pick up this parasite from infected slugs or snails, often by accident while eating grass or picking up toys left outside, and it can cause a clotting failure with spontaneous bleeding, including nosebleeds, sometimes alongside coughing, breathing difficulty or lethargy.
When to explore further
Whether the bleeding is from one nostril only or both, and whether it's a single episode versus something recurring over days, is useful descriptive detail.
Repeated sneezing episodes that bring up fresh blood over days, or bleeding paired with facial swelling or a change in the shape of the nose, point towards a process within the nasal passage, such as a growth or fungal infection.
At any age, bleeding alongside lethargy, appetite change or bruising elsewhere on the body points towards a whole-body process rather than a purely local one.
A nosebleed after known or possible access to rat or mouse poison fits a clotting failure. Bleeding usually starts 3 to 7 days after the poison is eaten, is often also happening out of sight in the chest, lungs or abdomen, and can become life-threatening within hours. Vets treat this pattern as a same-day assessment. In a dog, lungworm (Angiostrongylus vasorum) can also cause a clotting failure with nosebleeds. Dogs pick it up from slugs and snails, often by accident while eating grass or picking up toys left outside, so infection is possible even when no slug eating has been seen, and the clotting failure it causes can be life-threatening.
A nosebleed that is heavy, keeps going beyond a few minutes, or comes with pale gums, weakness, collapse or laboured breathing reflects significant blood loss or a clotting failure, which can become life-threatening within hours.
Noting the date, which nostril, and roughly how much blood was seen for each episode builds a timeline of how often bleeding recurs, though it does not show whether clotting is normal. A photo of any facial swelling or nasal discharge, and a note of any exposure to long grass or a recent tick attachment, adds useful context.
Last reviewed: 10 October 2026 · Dr Alastair Greenway MRCVS