Nostril Flare Cat: Causes, Warning Signs and Emergency Care

Nostril flare in cats — visible widening of the nostrils with each breath — is a significant respiratory sign that warrants careful attention. While a brief nostril flare in a cat that has been running or playing is normal, persistent or resting nostril flare in a cat signals increased respiratory effort and potential respiratory compromise. This article explains what nostril flare in cats means, what causes it, and when it requires urgent veterinary care. The nostril flare cat sign should always be assessed in context of the cat’s full respiratory pattern.

What Is Nostril Flare Cat? Signs and Definition

Nostril flare in cats (nasal alar flare) occurs when the muscles around the nostrils contract during inhalation, widening the nasal openings to increase airflow. In healthy cats at rest, breathing should be virtually imperceptible — quiet, effortless, and without visible nasal movement. When a cat nostril flare becomes visible at rest, it indicates the cat is working harder than normal to move air into its respiratory system. The nostril flare cat sign should always be assessed in context of the cat’s full respiratory pattern.

Nostril flare in cats is part of a constellation of increased respiratory effort signs that also includes abdominal breathing, extended neck posture, elbows held away from the body, and open-mouth breathing. Any of these signs at rest in a cat is a red flag. The nostril flare cat sign should always be assessed in context of the cat’s full respiratory pattern.

Normal vs Abnormal Nostril Flare Cat

Normal: Brief, mild nostril flare immediately after vigorous exercise or play that resolves within 1–2 minutes as the cat rests. A single nostril flare accompanying a deep breath or yawn is not concerning. The nostril flare cat sign should always be assessed in context of the cat’s full respiratory pattern.

Abnormal: Nostril flare in cats that occurs at rest, persists for more than a few minutes, worsens over time, or is accompanied by any of the following warning signs requires same-day or emergency veterinary evaluation: The nostril flare cat sign should always be assessed in context of the cat’s full respiratory pattern.

• Visible abdominal effort with each breath (belly moving exaggeratedly)
• Labored, noisy, or rapid breathing
• Open-mouth breathing (always abnormal in a resting cat)
• Blue, gray, or white gums (cyanosis — emergency)
• Extended neck with elbows away from the body (orthopnea position)
• Reluctance to lie down, preferring to remain upright
• Lethargy or reduced responsiveness alongside nostril flare in cats

8 Causes of Nostril Flare Cat

1. Nostril Flare Cat from Pleural Effusion

Pleural effusion is one of the most common causes of significant nostril flare in cats. Fluid accumulation in the pleural space compresses the lungs, dramatically reducing their ability to expand. Affected cats show progressive nostril flare, labored breathing, muffled heart sounds, and dull lung sounds on the ventral chest. Common causes in cats include chylothorax, pyothorax (infected fluid), feline infectious peritonitis (FIP), cardiac disease, and neoplasia. Thoracocentesis (draining the fluid) provides both diagnosis and immediate relief. The nostril flare cat sign should always be assessed in context of the cat’s full respiratory pattern.

2. Nostril Flare Cat from Feline Asthma

Feline asthma (allergic bronchitis) is a very common cause of episodic nostril flare in cats. Airway inflammation and bronchospasm cause sudden onset breathing difficulty — cats may crouch low with neck extended, showing visible nostril flare and abdominal effort. Acute asthma attacks in cats can be life-threatening and require immediate bronchodilator treatment (terbutaline or salbutamol). Long-term management involves inhaled corticosteroids via feline spacer devices. The nostril flare cat sign should always be assessed in context of the cat’s full respiratory pattern.

3. Nostril Flare Cat from Upper Respiratory Infection

Viral upper respiratory infections — most commonly feline herpesvirus (FHV-1) and calicivirus — cause nasal congestion, discharge, and sneezing that can contribute to nostril flare in cats as they work to breathe through congested nasal passages. Unlike lower respiratory causes, URI-related nostril flare is usually mild and accompanied by obvious nasal discharge, sneezing, and conjunctivitis rather than significant respiratory distress. The nostril flare cat sign should always be assessed in context of the cat’s full respiratory pattern.

4. Nostril Flare Cat from Pneumonia

Bacterial, viral, or aspiration pneumonia causes consolidation of lung tissue, reducing functional gas exchange and driving compensatory nostril flare in cats. Aspiration pneumonia — following anesthesia, forced feeding, or vomiting with inhalation — typically develops 12–36 hours after the inciting event. Chest radiographs showing an alveolar pattern in the cranioventral lung fields confirm the diagnosis. Aggressive antibiotic therapy and oxygen supplementation are required. The nostril flare cat sign should always be assessed in context of the cat’s full respiratory pattern.

5. Nostril Flare Cat from Cardiac Disease

Hypertrophic cardiomyopathy (HCM) — the most common cardiac disease in cats — can lead to congestive heart failure with pulmonary edema or pleural effusion, causing nostril flare in cats as a presenting sign. Affected cats may have had a previously detected heart murmur or gallop rhythm. Cardiac biomarkers (proBNP), echocardiography, and chest radiographs establish the diagnosis. Emergency diuretic therapy and oxygen support are required for acute decompensation.

6. Nostril Flare Cat from Nasopharyngeal Polyps

Nasopharyngeal polyps — benign inflammatory masses originating from the middle ear or Eustachian tube — can cause partial obstruction of the nasopharynx, resulting in chronic nostril flare in cats, stertor (snoring-like breathing), and nasal discharge. This is particularly common in young cats. CT imaging is the gold standard for assessment before surgical removal.

7. Nostril Flare Cat from Nasal Tumors

Nasal lymphoma and carcinoma are the most common nasal tumors in cats and can cause progressive nostril flare in cats through obstruction of nasal airflow. Other signs include unilateral or bilateral nasal discharge (often blood-tinged), facial deformity, sneezing, and nosebleeds (epistaxis). CT imaging and nasal biopsy are required for diagnosis and staging.

8. Nostril Flare Cat from Diaphragmatic Hernia

Traumatic diaphragmatic hernia — where abdominal organs herniate into the chest cavity — causes nostril flare in cats by limiting lung expansion. This is common following road traffic accidents or falls. Cats may present with acute respiratory distress or with chronic, gradually worsening nostril flare if the hernia is partial. Thoracic radiographs reveal abdominal organs in the chest. Surgical repair is required.

Emergency: Nostril Flare Cat Warning Signs

Go to an emergency veterinary clinic immediately — do not wait for a scheduled appointment — if your cat shows:

• Blue, white, or gray gums (oxygen deprivation)
• Open-mouth breathing at rest (always an emergency in cats)
• Nostril flare in cats combined with complete stillness and refusal to move
• Collapse or extreme weakness
• Rapid, shallow, or gasping breathing
• Progressive worsening of nostril flare over minutes to hours

How Vets Diagnose Nostril Flare Cat

• Observation and respiratory rate assessment — counting breaths per minute at rest; normal is 20–30 breaths/minute in cats
• Thoracic auscultation — identifies muffled sounds (effusion), crackles (pneumonia/edema), wheeze (asthma), or murmurs (cardiac)
• Chest radiographs — first-line imaging for pleural effusion, pneumonia, cardiac enlargement, masses
• Thoracic ultrasound (FAST scan) — rapid bedside assessment for pleural or pericardial fluid in unstable patients
• Echocardiography — cardiac structure and function; detects HCM, pericardial effusion
• Nasal endoscopy and CT — for suspected polyps, tumors, or chronic rhinitis
• Blood work and proBNP — distinguishes cardiac from non-cardiac causes of respiratory distress

Treatment Options for Nostril Flare Cat

• Oxygen therapy — immediate oxygen supplementation for any cat with significant nostril flare and respiratory distress; reduces the work of breathing while diagnostics proceed
• Thoracocentesis — needle drainage of pleural fluid provides rapid relief in cats with effusion-related nostril flare
• Bronchodilators — terbutaline (subcutaneous) or salbutamol inhaler for feline asthma
• Diuretics — furosemide for congestive heart failure-related pulmonary edema
• Antibiotics — for bacterial pneumonia or pyothorax
• Surgical intervention — polyp removal, diaphragmatic hernia repair, or nasal tumor debulking as indicated
• Inhaled corticosteroids — fluticasone via AeroKat spacer for long-term asthma control

For further guidance on feline respiratory conditions, the American Veterinary Medical Association (AVMA) and the Canadian Veterinary Medical Association (CVMA) publish owner resources on respiratory health in companion animals. See also our article on post-surgery breathing issues in cats and cat gulping and swallowing which can accompany respiratory distress.

Nostril Flare Cat: Frequently Asked Questions

Is nostril flare in cats always serious?
Brief nostril flare immediately after exercise is normal. Nostril flare in cats that occurs at rest, is persistent, or worsens is always worth veterinary evaluation. In cats, signs of respiratory effort should never be dismissed — feline respiratory reserve is limited and conditions can deteriorate rapidly.

My cat has a stuffy nose and nostril flare — could it just be a cold?
Yes — upper respiratory infections can cause mild nostril flare in cats from nasal congestion. However, if breathing is labored or the cat seems distressed, veterinary evaluation is needed even for apparent URIs, as secondary bacterial pneumonia can develop rapidly in cats.

What is a safe respiratory rate for a cat at rest?
Normal respiratory rate in cats at rest is 20–30 breaths per minute. Many veterinarians recommend that owners of cats with known heart disease count resting respiratory rate daily — a rate consistently above 30 breaths/minute warrants contact with the vet. Nostril flare in cats consistently accompanies rates above 40 breaths/minute.

Summary: Nostril Flare Cat

Nostril flare in cats at rest is a significant sign of increased respiratory effort that warrants prompt veterinary evaluation. The most common serious causes are pleural effusion, feline asthma, pneumonia, and cardiac disease — all of which require specific treatment. Any cat showing nostril flare combined with blue gums, open-mouth breathing, or extreme reluctance to move requires emergency care immediately. Early diagnosis and treatment give the best outcomes in feline respiratory disease.

Reviewed by the Vetpedia Veterinary Editorial Board. This article provides general clinical information and does not replace individualized veterinary advice. Always consult a licensed veterinarian for diagnosis and treatment of your pet.