Cartilagines nasi (Cartilago nasi lateralis dorsalis, Cartilago alaris)
The equine nasal cartilages are critical structural supports for the nasal passages. Horses are obligate nasal breathers; they cannot breathe through their mouths due to the long soft palate overlapping the epiglottis. The major cartilages include: the dorsal lateral nasal cartilage (cartilago nasi lateralis dorsalis), which supports the dorsal part of the nasal passage; the alar cartilage (cartilago alaris) with its lamina and cornu, which forms the framework of the nostril (naris) and allows active dilation during exercise; and the ventral lateral nasal cartilage. The alar cartilage is the most clinically important; its active dilation increases the nostril aperture by 70% during maximal exercise, reducing airway resistance. The false nostril (diverticulum nasi) is a blind-ended pouch located in the dorsolateral aspect of the nostril, formed between the nasal cartilages. At rest, the equine nostril is comma-shaped; during exercise, it becomes circular through active muscular dilation.
As obligate nasal breathers, any condition reducing nasal airflow directly impacts performance and can be life-threatening. The nasal passages should be evaluated endoscopically in any horse with abnormal respiratory noise, nasal discharge, or poor performance. Both nostrils should be examined as most structures are bilateral. Epistaxis (nosebleed) in an exercising horse is EIPH until proven otherwise, but unilateral resting epistaxis suggests local nasal pathology or guttural pouch disease.
Hemorrhage from the nostril(s) with multiple potential sources. EIPH (Exercise-Induced Pulmonary Hemorrhage) is the most common cause in performance horses; occurs in up to 75% of racehorses and resul
The character, laterality, timing, and volume of nasal discharge provide important diagnostic information. Serous (clear): normal, allergic, viral. Mucopurulent (thick, yellow-green): bacterial infect
The false nostril (nasal diverticulum) or alar fold can become entrapped or collapse during inspiration, creating a characteristic fluttering noise and increasing airway resistance. Most common in rac
Nasal polyps are benign pedunculated masses arising from the nasal mucosa that can obstruct airflow. Progressive ethmoid hematoma (PEH) is an expanding, encapsulated mass of hemorrhagic granulation ti
Collapse or inadequate dilation of the nasal passages during the high airflow demands of exercise. The alar cartilage may lack sufficient rigidity, or the dilator muscles may fatigue. This is a form o
NORMAL VS CONCERNING DISCHARGE: A small amount of clear, serous nasal discharge is normal, especially after exercise or in dusty conditions. CALL YOUR VET if you see: thick yellow/green discharge (especially unilateral), blood from the nostrils at rest, food material at the nostrils, foul-smelling discharge, or any discharge accompanied by fever, cough, or swollen lymph nodes. BREATHING SOUNDS: Horses should breathe quietly at rest. Normal exercise breathing increases in volume but should not include wheezing, roaring, whistling, or gurgling. Abnormal respiratory noise during exercise warrants evaluation with dynamic (exercising) endoscopy. NOSTRIL OBSERVATION: Learn what your horse's nostrils look like at rest and during exercise. Both nostrils should dilate equally. Asymmetric dilation or flaring at rest may indicate respiratory distress. EPISTAXIS (NOSEBLEED): A small amount of blood from one nostril after a bump or sneeze is usually minor. Significant or recurrent epistaxis; especially bilateral bleeding after exercise or spontaneous bleeding at rest; requires veterinary evaluation. Guttural pouch mycosis can cause fatal hemorrhage without warning. FLAIR STRIPS: Adhesive nasal dilator strips (FLAIR strips) are evidence-based aids that reduce nasal resistance during exercise, reduce EIPH severity, and help maintain oxygen levels during intense work. They are legal in most disciplines. DUST MANAGEMENT: Soak or steam hay, use low-dust bedding, ensure good barn ventilation; all help reduce nasal irritation and lower airway inflammation (equine asthma).
Hemorrhage from the nostril(s) with multiple potential sources. EIPH (Exercise-Induced Pulmonary Hemorrhage) is the most common cause in performance horses; occurs in up to 75% of racehorses and results from extreme pulmonary capillary pressure during intense exercise. Guttural pouch mycosis (Aspergillus fumigatus fungal infection eroding the internal carotid artery) causes potentially fatal hemorrhage. Ethmoid hematoma is a progressive, encapsulated mass of hemorrhagic tissue in the ethmoid labyrinth. Other causes: trauma, sinus disease, coagulopathy, and exercise-induced nasal congestion. Signs include: EIPH: bilateral epistaxis during or after intense exercise; blood may only be seen on endoscopy; poor performance. Guttural pouch mycosis: spontaneous unilateral epistaxis at rest (may be fatal); dysphagia; cranial nerve deficits (VII, IX, X, XI, XII). Ethmoid hematoma: progressive, intermittent, unilateral epistaxis; may see serosanguinous discharge; obstruction of nasal passage visible on endoscopy. Trauma: acute onset after injury, usually resolves
The character, laterality, timing, and volume of nasal discharge provide important diagnostic information. Serous (clear): normal, allergic, viral. Mucopurulent (thick, yellow-green): bacterial infection (sinusitis, strangles, pneumonia). Unilateral purulent: dental sinusitis (tooth root abscess draining into the maxillary sinus), sinus cyst, or nasal foreign body. Bilateral purulent: lower respiratory infection. Hemorrhagic: see epistaxis causes. Food material: dysphagia (choke, guttural pouch disease, cleft palate in foals). Signs include: Clear/serous: may be normal or early viral infection; bilateral suggests systemic cause. Yellow-green unilateral: think sinusitis or dental disease. Foul-smelling unilateral: strongly suggests tooth root abscess or necrotic mass. Bilateral purulent with fever and cough: lower airway disease. Food at nostrils: choke (esophageal obstruction) or dysphagia. Blood: see epistaxis. Frothy bilateral: pulmonary edema (emergency)
The false nostril (nasal diverticulum) or alar fold can become entrapped or collapse during inspiration, creating a characteristic fluttering noise and increasing airway resistance. Most common in racehorses and high-performance horses. Similar in concept to epiglottic entrapment but affecting the external nares. Can be corrected surgically by resection of the alar fold or false nostril tissue. Signs include: Abnormal respiratory noise (fluttering, snoring) during exercise, especially at high speeds; noise is typically inspiratory; may vary with head position; reduced performance; noise is loudest at the nostril level (can be confirmed by holding the nostril open during exercise to eliminate the noise); diagnosis confirmed with dynamic endoscopy during exercise
Nasal polyps are benign pedunculated masses arising from the nasal mucosa that can obstruct airflow. Progressive ethmoid hematoma (PEH) is an expanding, encapsulated mass of hemorrhagic granulation tissue originating from the ethmoid labyrinth that progressively fills the nasal cavity and/or paranasal sinuses. PEH is not a true neoplasm. Cause is unknown. Tends to recur after treatment. Most common in horses >6 years old. Signs include: Nasal polyp: unilateral nasal obstruction; stertor (snoring); serous to mucopurulent discharge; visible on endoscopy as smooth, pedunculated mass. PEH: intermittent unilateral epistaxis (hallmark); progressive unilateral nasal obstruction; may see bulging of facial bones in advanced cases; greenish to hemorrhagic, encapsulated mass on endoscopy; facial deformity in severe cases
Collapse or inadequate dilation of the nasal passages during the high airflow demands of exercise. The alar cartilage may lack sufficient rigidity, or the dilator muscles may fatigue. This is a form of dynamic upper airway obstruction. More recently recognized with the advent of exercising endoscopy (overground endoscope). May coexist with other dynamic airway obstructions. Signs include: Fluttering noise from nostrils at gallop; exercise intolerance; nostril collapse during inhalation; improved with nasal strips.; Inspiratory noise during intense exercise; noise originates at the nostril level; variable performance limitation; may be positional (worse with certain head/neck positions); more common in horses that work at high speeds; diagnosis requires exercising endoscopy showing dynamic collapse of nasal structures; external nasal dilator strips (FLAIR strips) may provide temporary relief
As obligate nasal breathers, any condition reducing nasal airflow directly impacts performance and can be life-threatening. The nasal passages should be evaluated endoscopically in any horse with abnormal respiratory noise, nasal discharge, or poor performance. Both nostrils should be examined as most structures are bilateral. Epistaxis (nosebleed) in an exercising horse is EIPH until proven otherwise, but unilateral resting epistaxis suggests local nasal pathology or guttural pouch disease.
NORMAL VS CONCERNING DISCHARGE: A small amount of clear, serous nasal discharge is normal, especially after exercise or in dusty conditions. CALL YOUR VET if you see: thick yellow/green discharge (especially unilateral), blood from the nostrils at rest, food material at the nostrils, foul-smelling discharge, or any discharge accompanied by fever, cough, or swollen lymph nodes. BREATHING SOUNDS: Horses should breathe quietly at rest. Normal exercise breathing increases in volume but should not include wheezing, roaring, whistling, or gurgling. Abnormal respiratory noise during exercise warrants evaluation with dynamic (exercising) endoscopy. NOSTRIL OBSERVATION: Learn what your horse's nostrils look like at rest and during exercise. Both nostrils should dilate equally. Asymmetric dilation or flaring at rest may indicate respiratory distress. EPISTAXIS (NOSEBLEED): A small amount of blood from one nostril after a bump or sneeze is usually minor. Significant or recurrent epistaxis; especially bilateral bleeding after exercise or spontaneous bleeding at rest; requires veterinary evaluation. Guttural pouch mycosis can cause fatal hemorrhage without warning. FLAIR STRIPS: Adhesive nasal dilator strips (FLAIR strips) are evidence-based aids that reduce nasal resistance during exercise, reduce EIPH severity, and help maintain oxygen levels during intense work. They are legal in most disciplines. DUST MANAGEMENT: Soak or steam hay, use low-dust bedding, ensure good barn ventilation; all help reduce nasal irritation and lower airway inflammation (equine asthma).
See the Nasal Cartilages on our interactive 3D horse model. Open 3D Model