SYMPTOM
Wheezing
An audible whistling or rasping sound during breathing, indicating narrowing or obstruction of the airways.
Feline asthma and bronchial disease
Wheezing in cats is frequently associated with feline asthma, a condition involving chronic inflammation and intermittent constriction of the lower airways. During an episode, the smooth muscle surrounding the bronchi contracts, narrowing the airway lumen and creating the characteristic whistling or wheezing sound as air is forced through the restricted passages. The inflammation may be triggered or worsened by environmental irritants such as dust, aerosol sprays, cigarette smoke, or certain types of cat litter. Episodes can range from mild, barely audible wheezing to severe respiratory distress with open-mouth breathing, which can be life-threatening, and the frequency and severity may vary considerably between individuals and over time within the same cat.
Allergic airway inflammation
Inhaled allergens (including pollens, mould spores and dust mites) and airborne irritants such as household chemicals can trigger inflammatory responses in the airways of susceptible animals, leading to mucosal swelling, increased mucus production, and bronchospasm. The resulting airway narrowing produces wheezing that may be seasonal or persistent depending on the nature of the exposure. In some animals, the allergic component is part of a broader pattern of atopy that may also involve skin signs, ear inflammation, or ocular discharge. The relationship between allergen exposure and wheezing may not always be obvious at first, as the inflammatory response can persist for hours or days after the initial trigger.
Upper airway obstruction
Structural or functional narrowing of the upper airways (including the nasal passages, pharynx, larynx, or trachea) can produce wheezing or stridor as air flows turbulently through the constricted area. In brachycephalic breeds, the combination of an elongated soft palate, narrowed nostrils, and a relatively small tracheal diameter can create chronic airflow resistance that manifests as wheezing, snoring, and noisy breathing. Tracheal collapse, most commonly seen in small-breed dogs, causes the tracheal rings to flatten during breathing, creating a dynamic obstruction that can produce wheezing particularly during excitement or exertion. Laryngeal paralysis, more common in older large-breed dogs, impairs the ability of the laryngeal cartilages to open fully during inspiration, creating turbulent airflow and audible respiratory noise.
Lower respiratory tract infection and chronic bronchitis
Bacterial, viral, or fungal infections involving the bronchi and lower airways can cause inflammation, mucus accumulation, and airway narrowing that produces wheezing. Infectious bronchitis may develop as a primary condition or as a secondary complication following viral respiratory infections that damage the airway epithelium. Chronic bronchitis in dogs, defined as a cough on most days for at least two months with no specific cause identified, often involves a component of airway inflammation and mucus hypersecretion that can produce wheezing alongside the characteristic cough. Fungal infections of the respiratory tract, while less common, can cause localised or diffuse airway inflammation, sometimes with wheezing.
Parasitic lung and airway disease
Certain parasites have life cycles that involve migration through or residence within the respiratory tract, causing inflammation and mechanical irritation that can produce wheezing. Lungworms, including Aelurostrongylus abstrusus in cats and Angiostrongylus vasorum or Oslerus osleri in dogs, can cause significant inflammation and damage in the airways and lungs. Adult Angiostrongylus vasorum live in the pulmonary arteries and the right side of the heart rather than in the airways, and infection can also cause bleeding disorders and sudden death. The parasitic burden may cause bronchial inflammation, mucus production, and airway constriction that creates wheezing sounds during breathing. Geographic location and lifestyle factors, particularly access to intermediate hosts such as slugs and snails, influence the likelihood of parasitic respiratory disease.
Cardiac-related respiratory compromise
Heart disease can secondarily affect the respiratory system through pulmonary oedema, possible pressure from enlarged cardiac chambers on the bronchi, or pulmonary hypertension altering blood flow through the lungs. Left-sided heart failure can cause fluid accumulation in the lung tissue, which may produce wheezing alongside coughing and increased respiratory effort. In dogs with an enlarged left atrium, coughing and wheezing have traditionally been attributed to pressure on the left mainstem bronchus, although a bronchoscopy study of 16 coughing dogs found airway collapse whether or not the left atrium was enlarged. The relationship between cardiac and respiratory signs can be complex, as the two systems are intimately interconnected, and primary disease in one frequently affects the other.
Why timing matters
Early observation
When wheezing is first observed, it may represent an acute episode triggered by a specific irritant, an early manifestation of a developing respiratory condition, or the first noticeable sign of a process that has been building subclinically. Initial episodes of wheezing are often intermittent and may resolve spontaneously, making it tempting to dismiss them as isolated events. However, the first occurrence often provides an opportunity to observe the circumstances surrounding the episode: what the animal was doing, what environmental factors were present, and how quickly the wheezing resolved. In some cases, early wheezing may be the only sign of airway inflammation before more overt respiratory difficulty develops. The animal's species, breed, age, and exposure history all influence the interpretation of a first episode of wheezing.
Later presentation
If wheezing persists or recurs with increasing frequency, the underlying airway process may be becoming chronic or progressive. Repeated episodes of bronchospasm and inflammation can lead to structural changes in the airways, a process sometimes called airway remodelling, in which the bronchial walls thicken, smooth muscle hypertrophies, and the airways become increasingly reactive to triggers. Chronic wheezing may be accompanied by exercise intolerance, persistent cough, increased respiratory rate at rest, and reduced overall activity. In cats with chronic asthma, the frequency and severity of episodes may increase over time, with the intervals between episodes shortening. The progression from intermittent to persistent wheezing often indicates that the inflammatory process has become established and may be more challenging to manage.
The trajectory of wheezing depends substantially on the underlying cause and the nature of trigger exposure. Allergic and asthmatic wheezing may follow a seasonal pattern, worsening during periods of high allergen load and improving when exposure decreases. Infectious causes may produce a relatively acute course with a defined period of wheezing that resolves as the infection clears, though some infections can transition to chronic bronchitis. Structural causes such as tracheal collapse or brachycephalic airway syndrome tend to follow a slowly progressive course, often worsening with age, weight gain, or in hot and humid conditions. Parasitic causes may fluctuate with the parasite's life cycle and the degree of reinfestation. Understanding whether wheezing is episodic, seasonal, progressive, or triggered by specific circumstances can help build a picture of the underlying process.
Conditions commonly associated
Feline Asthma
Feline asthma produces wheezing because airway inflammation narrows the passages the air must travel through, and air forced through this constricted space generates the whistling or rasping sound heard during breathing.
Tracheal Collapse in Dogs
Wheezing can accompany tracheal collapse, particularly when the collapse extends into the lower airways or when concurrent bronchomalacia narrows the bronchial passages.
Chronic Bronchitis in Dogs
Wheezing in chronic bronchitis results from turbulent airflow through narrowed bronchial airways, produced by bronchial wall thickening, mucus accumulation and collapse of weakened airways on breathing out.
Eosinophilic Bronchopneumopathy
Eosinophil infiltration inflames and thickens the lining of the bronchi. Cough is the main sign. A wheeze is one of several sounds sometimes heard through a stethoscope, and the chest can also sound normal.
Heartworm Disease in Cats
Wheezing reflects airway narrowing and bronchial inflammation triggered by the parasite's presence in the lung vessels, closely resembling feline asthma. Heartworm is not endemic in the UK, so this applies to cats that have travelled to, or been imported from, areas where it occurs.
Idiopathic Pulmonary Fibrosis in West Highland White Terriers
Idiopathic pulmonary fibrosis scars the lung tissue rather than the airways, and crackles heard through a stethoscope are the typical lung sound rather than a wheeze. Affected dogs also have airway changes, so a wheeze can be heard alongside.
When to explore further
When wheezing occurs repeatedly over days to weeks rather than as a single isolated episode, the recurrent pattern suggests an ongoing inflammatory or structural process in the airways. The triggering factor is either persistent or repeatedly encountered, and the pattern of recurrence (whether it occurs daily, weekly, or in clusters) can provide useful information about the nature and severity of the underlying process.
When wheezing is accompanied by increased respiratory effort (visible abdominal breathing, extended neck posture, flared nostrils, or a noticeable increase in breathing rate at rest), the airway compromise is affecting the animal's ability to ventilate efficiently. In a home study of healthy cats, the average sleeping breathing rate was consistently below 30 breaths a minute. The combination of wheezing with laboured breathing indicates a more significant degree of airway obstruction than wheezing alone. Open-mouth breathing in a cat, a tongue or gums turning blue, purple or pale, and weakness or collapse are signs of respiratory distress. Asthma attacks in cats can be life-threatening, and an obstructed upper airway in a dog can end in suffocation. How much oxygen is reaching the blood cannot be judged at home.
When wheezing develops in a cat that has not previously shown respiratory signs, particularly an indoor cat, the new onset may suggest the development of feline asthma or an allergic airway response. Indoor cats are exposed to a range of potential aeroallergens and airborne irritants including dust, mould, cleaning products, and litter dust, and the onset of wheezing in this context may point to an airway condition, an environmental trigger, or both.
When wheezing is accompanied by coughing, nasal discharge, reduced appetite, or lethargy, this cluster of respiratory and systemic signs may suggest an infectious process or a condition with broader health implications beyond the airways alone. The combination of airway signs with general malaise can help distinguish between localised airway irritation and a more systemic illness.
When wheezing worsens in specific environmental conditions (such as hot weather, high humidity, dusty environments, or following exposure to aerosol products), this pattern of environmental sensitivity can help identify trigger factors. Heat is a separate matter in dogs with a narrowed upper airway, such as flat-faced breeds and dogs with laryngeal paralysis or tracheal collapse. Dogs cool themselves by panting, so these dogs overheat more easily than others, and breathing that becomes noisier or more laboured in warm weather can become life-threatening. Animals whose wheezing has a clear environmental association may benefit from modifications to their living environment, and recognising these patterns can be a valuable part of understanding the overall picture.
Careful observation of when wheezing occurs, what appears to trigger or worsen it, and how quickly it resolves can build a detailed picture that is valuable for understanding the individual animal's respiratory pattern. Many owners find it helpful to note the timing of episodes, environmental conditions, the animal's activity level at onset, and any other signs that accompany the wheezing. For animals living indoors, considering potential airborne irritants (such as cleaning products, air fresheners, scented candles, or dusty litter) and observing whether changes to these factors influence the wheezing can also be informative. Each animal's respiratory health is shaped by individual factors including anatomy, immune sensitivity, environment, and overall condition, making observation and pattern recognition a meaningful foundation for understanding a mild, intermittent wheeze in an animal that is otherwise breathing comfortably. Laboured or open-mouth breathing is a different situation, and one that observation at home cannot assess.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS