Sinusitis in Horses: Nasal Discharge, Facial Swelling, and Treatment

Quick Answer
  • Sinusitis in horses is inflammation or infection of the sinus cavities and often causes discharge from one nostril, a bad odor, and sometimes facial swelling.
  • A common underlying cause is infection of an upper cheek tooth root, but sinus cysts, trauma, tumors, and other sinus disease can also be involved.
  • See your vet promptly if discharge lasts more than a few days, smells foul, becomes thick, or is paired with swelling, fever, reduced appetite, or noisy breathing.
  • Diagnosis often needs an oral exam, endoscopy, and skull imaging because treatment works best when the primary cause is found and addressed.
  • Many horses recover well when the source problem is treated, but advanced cases may need sinus lavage, tooth extraction, or standing sinus surgery.
Estimated cost: $350–$4,500

What Is Sinusitis in Horses?

Sinusitis is inflammation or infection inside the air-filled sinus cavities of a horse's skull. Horses have several paired sinuses, and disease in these spaces often shows up as unilateral nasal discharge, meaning drainage from one nostril rather than both. The discharge may be thick, pus-like, blood-tinged, or foul-smelling.

In many horses, sinusitis is secondary to another problem rather than a stand-alone disease. Upper cheek tooth root infection is one of the most common triggers because the roots sit close to the maxillary sinuses. Cysts, trauma, masses, and other sinus disorders can also block drainage and allow infection to build.

Some horses only have mild discharge at first. Others develop facial swelling, noisy breathing, reduced airflow through one nostril, or discomfort when the face is touched. Because the signs can overlap with dental disease, respiratory infection, and more serious sinus conditions, your vet usually needs to look for the underlying cause before recommending treatment.

Symptoms of Sinusitis in Horses

  • Discharge from one nostril
  • Foul-smelling nasal discharge or breath
  • Facial swelling or asymmetry
  • Reduced airflow through one nostril
  • Noisy breathing or snoring-type respiratory noise
  • Pain when the face is touched
  • Poor appetite, dropping feed, or chewing changes
  • Fever, dullness, or reduced performance
  • Bloody discharge

Call your vet sooner rather than later if your horse has nasal discharge that lasts more than a few days, smells bad, or comes with facial swelling. Sinus disease in horses is often easier to manage before thick material, dental damage, or chronic inflammation build up.

See your vet immediately if your horse has trouble breathing, significant facial deformity, fever, marked pain, heavy bleeding from the nose, or suddenly stops eating. Bilateral discharge can also point to a different problem, including contagious respiratory disease, so isolation may be appropriate until your vet advises next steps.

What Causes Sinusitis in Horses?

One of the leading causes of sinusitis in horses is dental disease, especially infection involving the roots of the upper cheek teeth. Because those roots sit close to the sinus cavities, infection can spread upward and create a persistent, often foul-smelling discharge. Horses with dental-related sinusitis may also have trouble chewing, quidding, or swelling over the face or jaw.

Sinusitis can also develop when normal drainage is blocked. This may happen with sinus cysts, trauma, fractures, foreign material, or masses such as tumors. In these cases, fluid and inflammatory debris collect in the sinus and create an environment where infection can persist.

Less commonly, sinus inflammation may follow upper respiratory disease or other nasal problems. Your vet may describe the condition as primary sinusitis when the sinus itself is the main issue, or secondary sinusitis when another disease process caused it. That distinction matters because antibiotics alone may not solve the problem if a diseased tooth, cyst, or obstructive lesion is still present.

How Is Sinusitis in Horses Diagnosed?

Diagnosis starts with a physical exam and a close look at the discharge, facial symmetry, airflow, temperature, and overall comfort. Your vet will usually ask how long the problem has been present, whether it is coming from one nostril or both, and whether there are signs of dental pain, weight loss, or recent trauma.

Because dental disease is such a common cause, many horses need a sedated oral exam. Your vet may also recommend endoscopy to inspect the nasal passages and drainage openings, along with skull radiographs to look for fluid lines, tooth root changes, bone changes, or masses. In referral settings, CT can be especially helpful for complex or chronic cases because it shows the teeth and sinus compartments in much greater detail.

Additional testing may include sinus fluid sampling, culture in selected cases, or direct examination of the sinus with sinoscopy. These steps help your vet decide whether the horse may respond to medical care, needs a diseased tooth removed, or would benefit from sinus lavage or surgery.

Treatment Options for Sinusitis in Horses

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$350–$900
Best for: Mild early cases, horses with stable signs, or pet parents who need to start with the most focused diagnostics and treatment first.
  • Farm call or clinic exam
  • Basic physical exam and temperature check
  • Sedation if needed for a limited oral exam
  • Targeted anti-inflammatory care and supportive management as directed by your vet
  • Empirical antimicrobial therapy when your vet feels bacterial sinus infection is likely
  • Short-term monitoring for response
Expected outcome: Fair to good if the problem is uncomplicated and improves quickly, but recurrence is common if an infected tooth or obstructive sinus problem is still present.
Consider: Lower upfront cost, but it may miss the primary cause. Horses with dental disease, cysts, or chronic thick discharge often need imaging and more definitive treatment.
Most Common

Recommended Standard Treatment

$900–$2,200
Best for: Most horses with persistent unilateral discharge, foul odor, facial swelling, or suspected dental sinusitis.
  • Complete exam plus sedated oral examination
  • Skull radiographs
  • Nasal endoscopy when available
  • More targeted antimicrobial and anti-inflammatory plan based on exam findings
  • Sinus trephination or lavage in selected standing cases
  • Dental treatment or extraction planning if an upper cheek tooth root is involved
Expected outcome: Good in many horses when the underlying cause is identified and treated. Dental-related cases often improve well once the diseased tooth and infected sinus contents are addressed.
Consider: Higher cost and more procedures than conservative care, but it usually gives a clearer diagnosis and a better chance of lasting control.

Advanced / Critical Care

$2,200–$4,500
Best for: Chronic, recurrent, severe, or complicated cases, especially when there is facial deformity, poor response to first-line care, suspected mass, or difficult dental disease.
  • Referral hospital evaluation
  • Advanced imaging such as CT
  • Sinoscopy or standing sinus surgery
  • Sinusotomy or bone flap procedure for drainage and access
  • Complex dental extraction or treatment of cysts, masses, or severe chronic infection
  • Hospitalization, repeated lavage, and intensive follow-up care
Expected outcome: Variable but often good for treatable dental and drainage problems. Prognosis is more guarded when tumors, extensive bone destruction, or severe chronic disease are present.
Consider: Most complete workup and widest range of treatment options, but requires the highest cost range, more handling, and sometimes referral-level equipment or surgery.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Sinusitis in Horses

Bring these questions to your vet appointment to get the most out of your visit.

  1. You can ask your vet whether the discharge pattern suggests sinusitis, dental disease, or a contagious respiratory problem.
  2. You can ask your vet if a sedated oral exam is needed to look for an upper cheek tooth root infection.
  3. You can ask your vet which imaging option makes the most sense first: radiographs, endoscopy, or referral for CT.
  4. You can ask your vet whether antibiotics alone are likely to help or whether the sinus needs drainage or lavage.
  5. You can ask your vet if facial swelling changes the urgency or points toward a cyst, fracture, or mass.
  6. You can ask your vet what signs would mean the condition is worsening and needs immediate recheck.
  7. You can ask your vet what the realistic cost range is for conservative, standard, and advanced care in your area.
  8. You can ask your vet how likely recurrence is if the underlying cause is dental or structural.

How to Prevent Sinusitis in Horses

Not every case can be prevented, but routine dental care is one of the most practical ways to lower risk. Regular oral exams help your vet catch sharp points, abnormal wear, fractured teeth, and early dental infection before a tooth root problem spreads into the sinus.

Prompt attention to nasal discharge, facial swelling, bad odor, or chewing changes also matters. Waiting to see if it clears on its own can allow infection and trapped debris to become more established. Early treatment is often less invasive than managing a chronic case.

Good barn management supports respiratory health too. Reduce dust exposure when possible, keep feed and bedding clean, and address facial trauma quickly. If your horse develops bilateral discharge, fever, or signs of infectious respiratory disease, isolate as advised and involve your vet so contagious causes are not missed.

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