Feline Asthma: 10 Things You Should Know in 2026

Philip R Judge BVSc MVS PG Cert Vet Stud MACVS (VECC, Medicine of Dogs)

1. Diagnosis requires a multimodal approach

Feline asthma cannot be diagnosed by a single test. 

1. A diagnosis should ideally be based on history, clinical examination, thoracic imaging, and bronchoalveolar lavage fluid (BALF) cytology. 
2. Thoracic radiographs may be unremarkable in 17% to 23% of affected cats, and the severity of radiographic findings does not necessarily correlate with clinical severity. The most commonly described radiographic abnormality is a bronchial pattern caused by bronchial wall thickening and mucus accumulation. Broncho-intestinal patterns, pulmonary hyperinflation, and atelectasis of the right middle lung lobe are also possible but less common. 
3. CT is more sensitive and specific than radiography, and may reveal segmental and subsegmental bronchial wall thickening, bronchiectasis, atelectasis, and increased lung parenchymal density. CT findings can also overlap with other diseases such as lungworm or heartworm infection, so a reliable diagnosis cannot be made with CT alone.

2. Bronchoalveolar lavage cytology is central to diagnosis – but may lack specificity

Eosinophilic airway inflammation is characteristic of feline asthma. 

1. Percentages of eosinophilic granulocytes in BALF greater than 10% to 20% support the diagnosis. However, healthy cats may also have eosinophils in the lower airways, and cut-off values for optimal sensitivity remain controversial
2. The predominant cell type in healthy cats is alveolar macrophages. 
3. BALF should ideally be collected from two to three different lung areas, as differential cell counts may vary between lung lobes and depending on the number of lavage samples. Cytology should be performed promptly due to storage-related alterations. 
4. Additional testing should include bacteriological culture and Mycoplasma species PCR to rule out bacterial bronchitis or secondary bacterial involvement. 
5. PCR for lungworms and fungal organisms can also be performed if indicated.

3. Inhaled corticosteroids are the mainstay of long-term therapy

Inhaled corticosteroids are recommended for long-term management to minimise systemic side effects. 

Prolonged use of systemic corticosteroids carries significant risk, including diabetes mellitus, heart failure, immunosuppression, and increased risk of infections.

Systemic corticosteroid doses:

• Prednisolone: 0.5–1 (up to 2) mg/kg every 12–24 hours orally
• Dexamethasone: 0.1–0.2 (up to 0.4) mg/kg once daily intravenously or subcutaneously
• Methylprednisolone acetate: 2–5 mg/kg once every 4–8 weeks intramuscularly or subcutaneously

Inhaled corticosteroids are delivered using valved holding chambers (spacers) with tight-fitting face masks. While side effects are fewer than with systemic corticosteroids, some systemic absorption still occurs via the oropharynx and lower airways. In one study, 3 out of 15 cats treated with 400 micrograms of inhaled budesonide twice daily showed evidence of hypothalamic-pituitary-adrenal axis suppression on ACTH stimulation testing, despite no clinical signs of hypercortisolism. 

Inhaled corticosteroid doses:

• Fluticasone propionate: 44–250 micrograms every 12 hours by inhalation
• Flunisolide: 250 micrograms every 12 hours by inhalation
• Beclomethasone propionate: 80–166 micrograms every 12 hours by inhalation
• Budesonide: 100–200 (up to 400) micrograms every 12 hours by inhalation

Side effects reported with long-term corticosteroid use include polyphagia, polyuria, polydipsia, diabetes mellitus, and fungal infection or demodicosis of the muzzle.

4. Bronchodilators are for acute relief and adjunctive use only

Bronchodilators reverse bronchoconstriction of bronchial smooth muscle and are important for emergency management of acute respiratory distress. They should not be used as monotherapy long-term because they have no or only weak anti-inflammatory properties, and therefore fail to manage the underlying disorder. However, they are useful as adjunctive therapy alongside corticosteroid use.

Systemic bronchodilator doses:

• Terbutaline: 0.01 mg/kg every 6–8 hours subcutaneously, intramuscularly, or intravenously (emergency treatment, or pre-bronchoscopy/BAL); for long-term treatment: 0.625–1.25 mg per cat every 12 hours orally
• Extended-release theophylline: 20 mg/kg once daily orally (given in the evening) or 10 mg/kg every 12 hours orally
• Propentofylline: 5 mg/kg every 12 hours orally

Inhaled bronchodilator doses:

• Salbutamol (albuterol): 90–200 micrograms every 6–8 to 12 hours by inhalation (emergency treatment)
• Salmeterol: 25–50 micrograms every 12 hours by inhalation

Combination aerosols (corticosteroid + bronchodilator):

• Fluticasone propionate/salmeterol: 125/25 micrograms or 250/50 micrograms every 12 hours by inhalation
• Fluticasone propionate/formoterol: 125/5 micrograms or 250/10 micrograms every 12 hours by inhalation

In severe bronchoconstriction, delivery of inhaled bronchodilators to the site of action may be impaired, so injectable terbutaline is recommended as an alternative emergency drug. Inhaled ipratropium and salbutamol have been shown to have a synergistic spasmolytic effect in research cats.

5. Environmental modification is an essential component of management

Owners should be advised to reduce potential triggers and irritants in the cat’s environment. Avoid cigarette or e-cigarette smoke, open fireplaces, strong cleaning detergents, dusty cat litter, and perfumed candles or air fresheners. A study in Taiwan showed a significant correlation between airway disease and indoor air pollution. Reactions to common indoor allergens such as house dust mite antigen were common in studies assessing allergen responses in asthmatic cats. Dietary modification to a hypoallergenic diet may be helpful, particularly if other signs of atopy are present, such as atopic skin or food-responsive gastrointestinal disease.

6. Allergy testing has limited clinical utility at present

While sensitisation to aeroallergens has been identified in many cats with asthma, results of serum allergen-specific immunoglobulin E testing and intradermal skin testing do not correlate well in naturally affected cats. Both tests can yield positive reactions in healthy cats, and healthy cats may show positive immunoglobulin E responses following sensitisation to allergens. Interpretation should always be undertaken in the context of clinical signs, environmental factors, and allergen exposure. 

Identification of relevant allergens may enable allergen avoidance or allergen-specific immunotherapy, with both tests potentially serving as tools for selecting allergens for immunotherapy, but evidence for this approach in naturally occurring disease is scarce.

7. Newer and alternative therapies show promise but lack strong evidence

Several treatments have been evaluated, mostly in experimental models:

• Cyclosporine: 5–10 mg/kg orally every 12 hours. One case report described successful treatment of a cat with asthma, heart failure, and diabetes mellitus. However, studies in experimental models have shown conflicting results, with one showing decreased airway hyperresponsiveness and eosinophilia and another showing no effect. Therapeutic drug monitoring is recommended due to extreme variability in absorption and metabolism.
• Masitinib: 50 mg per cat once daily orally. A tyrosine kinase receptor blocker, it significantly reduced BALF eosinophils and improved respiratory compliance in experimentally induced asthma. However, significant proteinuria was a major side effect.
• Nebulised lidocaine: 2 mg/kg of a 2% solution every 8 hours by inhalation. It decreased airway hyperresponsiveness but not BALF eosinophils. It is well tolerated, and may potentially be considered as an adjunctive therapy.
• Mesenchymal stem cells: Adipose-derived mesenchymal stem cells administered intravenously in experimental models showed decreased airway eosinophilia, hyperresponsiveness, and bronchial wall thickening on CT in one study, but another study over one year showed no difference in eosinophilia or hyperresponsiveness compared with placebo, though CT illness scores were improved.
• Allergen-specific immunotherapy: Reports in naturally occurring disease are scarce. One abstract described 8 out of 12 cats with suspected asthma becoming subclinical after several months of immunotherapy. If utilised, concomitant systemic glucocorticoids should be avoided as they diminish efficacy; inhaled corticosteroids are preferred.

8. Monitoring response to therapy can be aided by barometric whole-body plethysmography

Barometric whole-body plethysmography is a non-invasive method that assesses airway hyperreactivity, a characteristic feature of feline asthma. Parameters such as Penh and PEF/EF50 can be elevated in asthmatic cats. Bronchial provocation using Carbachol or adenosine 5′-monophosphate can increase the sensitivity of measurements. The technique is well tolerated by cats. However, its use in clinical practice is currently limited by the need for specialised equipment and expertise, and the significance of results requires clarification.

9. Cats with asthma are typically younger than those with chronic bronchitis

Signalment may provide a clue to diagnosis. Cats with feline asthma are usually younger compared with cats with chronic bronchitis, which is characterised by predominantly neutrophilic airway inflammation on BALF cytology (as opposed to eosinophilic inflammation in asthma). 

A breed predisposition has been suggested in Siamese cats. 

10. Emergency management focuses on stabilisation with oxygen, corticosteroids, and bronchodilators

In cats presenting with acute respiratory distress, stabilisation should include:

• Oxygen supplementation
• A short-acting corticosteroid (e.g. dexamethasone 0.1–0.2 mg/kg intravenously or subcutaneously)
• A bronchodilator (e.g. terbutaline 0.01 mg/kg subcutaneously, intramuscularly, or intravenously; or inhaled salbutamol 90–200 micrograms)

Injectable terbutaline may be preferred over inhaled salbutamol in severe bronchoconstriction, as delivery of inhaled drugs to the site of action may be impaired due to severe bronchoconstriction. Inhaled salbutamol combined with ipratropium has been shown to reduce bronchoscopy and BAL-induced bronchoconstriction in allergen-sensitised cats, and this combination has been suggested for pre-treatment before these procedures.

Long-term management then shifts to anti-inflammatory treatment to prevent tissue remodelling. Initial treatment with oral prednisolone followed by management with inhaled fluticasone has been shown to significantly reduce clinical signs and airway eosinophilia in pet cats.

Reference:

Gareis H, Schulz B. Feline Asthma—Update on Diagnosis and Treatment Recommendations. Veterinary Clinics: Small Animal Practice. 2026 Jul 1;56(4):971-93.