Ethmoid Hematoma in Horses: Recurrent Nosebleeds and Nasal Discharge
- Ethmoid hematoma, often called progressive ethmoid hematoma, is a benign but locally destructive mass in the nasal passages or sinuses of horses.
- The most common sign is intermittent one-sided nosebleeding, though some horses also develop nasal discharge, noisy breathing, reduced airflow, or facial swelling.
- Diagnosis usually involves upper airway endoscopy and skull imaging. CT can help define how far the mass extends before treatment.
- Treatment depends on size and location. Options may include repeat endoscopic formalin injections, laser ablation, or sinus surgery, and recurrence is fairly common even after treatment.
- See your vet promptly if your horse has repeated nosebleeds, worsening discharge, trouble breathing, or signs of significant blood loss.
What Is Ethmoid Hematoma in Horses?
Ethmoid hematoma in horses, more precisely called progressive ethmoid hematoma (PEH), is a non-cancerous mass that develops in the ethmoid region at the back of the nasal passages and sometimes extends into the paranasal sinuses. Even though it is benign, it can still cause important problems because it slowly expands, bleeds, and takes up space inside the airway.
These masses are usually dark red, green, yellow, or purple on endoscopy because they contain blood products and fibrous tissue. Over time, they can irritate nearby tissue, obstruct airflow, and lead to repeated episodes of one-sided nosebleeds. Middle-aged horses are reported more often, but PEH can occur in a range of adult horses.
For many pet parents, the first clue is a horse that seems normal between episodes and then suddenly has blood from one nostril again. That pattern matters. Recurrent, intermittent bleeding is more concerning for an internal nasal problem like PEH than for a minor scrape or brief irritation.
Because PEH can recur after treatment and may extend farther than it first appears, your vet may recommend both endoscopy and imaging before choosing a care plan. That helps match treatment intensity to the lesion's size, location, and your horse's needs.
Symptoms of Ethmoid Hematoma in Horses
- Intermittent bleeding from one nostril
- Persistent or recurrent nasal discharge, sometimes blood-tinged
- Reduced airflow through one nostril
- Noisy breathing or abnormal respiratory sounds
- Foul-smelling breath or nasal odor
- Facial swelling or deformity
- Exercise intolerance or decreased performance
- Pale gums, weakness, or larger-volume bleeding episodes
Repeated nosebleeds are the symptom that most often brings horses with ethmoid hematoma to your vet. A single small nosebleed can happen for many reasons, but recurrent one-sided bleeding deserves a workup. Some horses also have discharge, reduced airflow, or noisy breathing before the diagnosis is made.
See your vet immediately if bleeding is heavy, your horse seems weak, breathing is harder than normal, or the face looks swollen. Those signs can mean the lesion is larger, bleeding more actively, or affecting the airway.
What Causes Ethmoid Hematoma in Horses?
The exact cause of progressive ethmoid hematoma is still not fully understood. Veterinary references describe it as a locally destructive, encapsulated mass of the nasal passages or paranasal sinuses with uncertain etiology. In other words, experts know what it looks like and how it behaves, but not exactly why one horse develops it and another does not.
What is known is that the lesion forms from tissue in the ethmoid area and contains repeated bleeding and organization of blood within fibrous tissue. It is not considered a cancer, but it can still enlarge over time and damage nearby structures. Some cases stay mainly within the nasal passage, while others extend into the sinus compartments.
Because the cause is unclear, this is not something most pet parents could have prevented through routine management. It is also not the same as a simple nose injury. If your horse has repeated unilateral nosebleeds, your vet will also consider other causes such as sinus cysts, infection, trauma, guttural pouch disease, or tumors, which is why a full diagnostic workup matters.
How Is Ethmoid Hematoma in Horses Diagnosed?
Diagnosis usually starts with a physical exam and a detailed history, especially how often the bleeding happens, whether it is from one nostril, and whether there are changes in breathing or performance. Your vet will often recommend upper airway endoscopy, which can allow direct visualization of a smooth, discolored mass in the ethmoid region or blood coming from that area.
Imaging is the next step in many horses. Skull radiographs can help identify sinus involvement, fluid, or a soft tissue mass, while CT is often the most useful advanced imaging test when available because it shows the lesion's full extent and helps with treatment planning. This is especially important before formalin injection or surgery, since some lesions extend farther than expected.
Additional testing may include bloodwork to assess blood loss or overall health before sedation or surgery. In selected cases, your vet may discuss biopsy or sampling, but the approach depends on the lesion's location and bleeding risk. The main goal is to confirm the diagnosis, rule out other causes of epistaxis, and choose the least invasive option that still fits the case well.
Treatment Options for Ethmoid Hematoma in Horses
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm call or clinic exam
- Sedation and upper airway endoscopy
- Baseline bloodwork if bleeding has been recurrent
- Repeat monitoring exams
- In some appropriate small, accessible lesions: endoscopically guided intralesional 4% formalin injection, often requiring multiple treatments
Recommended Standard Treatment
- Referral-level endoscopy
- Skull radiographs and/or CT when available
- Treatment planning based on lesion size and location
- Endoscopic laser ablation for reachable lesions or formalin injection when appropriate
- Post-procedure medications such as NSAIDs and, in some cases, antimicrobials
- Scheduled recheck endoscopy to monitor for recurrence
Advanced / Critical Care
- Hospital-based care and advanced imaging such as CT
- Standing or general anesthesia procedures depending on approach
- Sinus surgery or sinusotomy for large, obstructive, or sinus-extending lesions
- Radical debridement of the lesion's origin when feasible
- Management of surgical bleeding, nasal or sinus packing, and possible transfusion planning
- Postoperative hospitalization, medications, and follow-up endoscopy/imaging
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Ethmoid Hematoma in Horses
Bring these questions to your vet appointment to get the most out of your visit.
- Does my horse's bleeding pattern fit progressive ethmoid hematoma, or are other causes still high on the list?
- What did you see on endoscopy, and do you suspect the lesion is limited to the nasal passage or extending into the sinuses?
- Would radiographs be enough for this case, or would CT meaningfully change treatment planning?
- Is my horse a candidate for endoscopic formalin injection, laser treatment, surgery, or more than one option?
- What recurrence risk should I expect with each treatment option in my horse's specific case?
- What signs at home would mean the bleeding or breathing has become urgent?
- How often should we schedule recheck endoscopy after treatment?
- What total cost range should I plan for, including repeat procedures or follow-up visits?
How to Prevent Ethmoid Hematoma in Horses
There is no proven way to fully prevent progressive ethmoid hematoma because the underlying cause is not well defined. Good routine care still matters, but this is not a condition with a known vaccine, supplement, or management change that reliably stops it from developing.
The most practical form of prevention is early detection of recurrence or progression. If your horse has had unexplained one-sided nosebleeds before, do not assume a new episode is minor. Prompt re-evaluation gives your vet the best chance to identify a lesion while it is still smaller and potentially easier to manage.
After treatment, follow-up is especially important because recurrence is common. Keep notes on any bleeding episodes, discharge, breathing noise, or exercise changes, and share those details with your vet. That history can help guide whether monitoring, repeat endoscopy, or another treatment step makes sense.
Routine barn management still supports overall respiratory health. Reducing dust exposure, keeping stalls well ventilated, and addressing other nasal or sinus problems early may help your horse stay more comfortable, even though these steps do not specifically prevent PEH.