SYMPTOM
Coughing up blood or foam
The animal coughs and either blood or a pink, frothy fluid is seen in the mouth or on nearby surfaces, distinct in appearance from a routine dry or productive cough.
Congestive Heart Failure
When the heart is no longer pumping efficiently, fluid can back up into the lung tissue and airways, producing the pink, frothy character described here; this is more common in small-breed older dogs with degenerative mitral valve disease and in cats with an underlying heart muscle condition.
Lungworm (Angiostrongylus Vasorum)
This parasite, present across much of the UK and spread via slugs and snails, lives within the pulmonary blood vessels and can disrupt normal clotting as well as directly irritate lung tissue, making haemoptysis a recognised presenting sign in affected dogs.
Airway Irritation Or Mechanical Trauma
A single, forceful coughing fit, a grass seed or other small foreign material scratching the airway lining, or a bout of infectious tracheobronchitis can produce streaks of blood-tinged sputum from local capillary irritation alone, without reflecting deeper lung or heart disease.
Pneumonia
Infection and inflammation within the lung tissue can affect small blood vessels enough that coughing dislodges blood-tinged material alongside the more typical signs of a chesty, productive cough.
Anticoagulant Rodenticide Exposure
Impaired clotting following exposure to rat and mouse poison can allow spontaneous bleeding into the airways, sometimes as one of several sites of bleeding around the body.
Lung Tumour
A mass within the lung tissue, more often seen in older animals, can bleed as it grows or as the surrounding tissue is disrupted by coughing, and tends to be considered when episodes are recurrent rather than a single isolated event.
Blunt Chest Trauma
A blunt injury to the chest, such as from a road traffic incident, a fall, or a kick, can bruise the lung tissue itself, a process called pulmonary contusion, and this is thought to be among the more frequently identified causes of this sign overall. Bleeding into the airways can appear as coughing up blood or frothy, blood-tinged fluid even when there is no visible wound on the outside of the chest, and the cough sometimes only becomes noticeable some hours after the injury as bruising within the lung develops.
Why timing matters
Early observation
A single streak of blood-tinged material after one particularly hard coughing fit often reflects local irritation of the airway lining from the mechanical act of coughing itself.
Later presentation
Coughing that recurs, especially where the material has a pink, frothy character rather than simple streaking, points more toward a process affecting the lung tissue or heart rather than the airway surface alone.
Several of the underlying processes here, including heart failure and lungworm, tend to build gradually over days to weeks, so the trend in frequency and character of episodes over that window generally carries more information than any single occurrence.
Conditions commonly associated
Congestive Heart Failure in Dogs
Fluid backing up into the lungs from reduced cardiac function produces the pink, frothy character described in this presentation.
Mitral Valve Disease in Dogs
This degenerative valve condition is a common underlying driver of the heart failure that can lead to pink frothy coughing in older small-breed dogs.
Hypertrophic Cardiomyopathy in Cats
This heart muscle condition can progress to fluid build-up in the lungs with a similar presentation in cats.
Angiostrongylus (Lungworm)
This parasite affects pulmonary blood vessels and clotting, making haemoptysis a recognised sign of infection.
Pneumonia
Inflammation within lung tissue can affect small vessels enough to produce blood-tinged material when coughing.
Anticoagulant Rodenticide Toxicity
Impaired clotting from rodenticide exposure can allow spontaneous bleeding into the airways.
When to explore further
A faster resting breathing rate or visibly increased effort alongside the coughing may add useful information beyond the cough itself.
Reduced enthusiasm for exercise, unusual tiredness, or pale gum colour occurring around the same time as the coughing broadens the picture beyond the airway alone.
Known or possible access to rodenticide bait, or unsupervised time in areas where it may have been placed, is relevant context worth noting.
Bruising, nosebleeds, or blood in the urine occurring alongside the cough points toward a clotting-related mechanism rather than a purely local one.
Episodes that recur on more than one occasion, rather than a single isolated event, generally carry more weight than a one-off finding.
Any known or witnessed knock, fall, road traffic incident, or fight occurring in the hours before the coughing began is relevant background, even where no external injury is visible.
Filming an episode, together with a count of resting breaths per minute while the animal is settled and not panting, gives a useful baseline to track. Noting the colour and texture each time (a streak versus a frothy pink versus frank blood) and keeping a simple log of frequency and exercise tolerance builds a picture over successive days. Any known or possible access to rodenticide is worth recording as background context.
Last reviewed: 13 September 2026 · Dr Alastair Greenway MRCVS