Nasal Discharge in Horses
Nasal discharge ranges from clear, watery fluid to thick, yellow–green pus or blood. Colour, smell, and whether the discharge is from one nostril (unilateral) or both (bilateral) help narrow likely causes. Fever, foul odour, laboured breathing, or swelling are red-flag features that need prompt veterinary advice.
In the first hour
Start with a temperature and full vitals (heart rate, respiratory rate, mucous membranes and capillary refill time). Note discharge colour/consistency, odour, volume, and laterality (one vs both nostrils). Look for cough, facial/sinus pain, dysphagia, or exercise intolerance. If fever or thick/colored discharge is present, isolate the horse, use dedicated buckets/equipment, and avoid nose-to-nose contact. Do not flush the nose or give medications unless your veterinarian directs you. Call your veterinarian the same day for thick or foul-smelling discharge, facial swelling/pain, dysphagia, or any discharge with fever or breathing effort.
First 12-Hour Owner Plan
Focus on monitoring, isolation if indicated, and clear records for your veterinarian. Avoid starting medications unless directed.
Log vitals every 2–4 hours
Record temperature, heart and respiratory rates, mucous membranes and capillary refill time. Note cough or breathing effort.
Track discharge characteristics
Note colour (clear/white/yellow–green/bloody), thickness, odour, volume, and whether unilateral or bilateral. Photograph changes.
Maintain isolation if fever or thick discharge
Dedicated buckets and tools, avoid nose-to-nose contact, handle this horse last, and wash hands/boots.
Optimize environment
Reduce dust (soaked hay, good ventilation), provide fresh water, and keep the head at a natural height to aid drainage.
Re-check face and mouth
Gently assess for facial/sinus pain or swelling and look for dental issues or feed packing that may suggest sinus or tooth involvement.
Report trends to your veterinarian
Share your vitals log, discharge notes, recent travel/new arrivals, vaccination status, and any photos or short video.
First-hour plan: owner-safe steps
01
Check temperature and vitals
Record rectal temperature, heart and respiratory rates, mucous membranes and capillary refill time. Note any cough or breathing effort.
02
Describe the discharge
Colour (clear, white, yellow–green, bloody), thickness, odour, volume, and whether it’s from one or both nostrils. Photograph if safe.
03
Start simple biosecurity
If fever or thick/colored discharge is present, isolate the horse, dedicate buckets/tools, avoid nose-to-nose contact, and handle this horse last.
04
Water is OK; avoid unnecessary drugs
Offer fresh water. Do not start medications or flush the nose unless your veterinarian instructs you—some drugs mask important signs.
05
Check for facial pain or swelling
Gently compare both sides of the face/sinuses and mandibles. Pain, swelling, malodour, or dysphagia increase urgency.
06
Call your veterinarian
Same day for thick/foul discharge, fever, cough with effort, facial swelling/pain, difficulty swallowing, or discharge after recent travel/new arrivals.
Red Flags: When to Call or Trailer Now
These signs need immediate veterinary guidance. Follow your veterinarian’s transport advice—some cases are safer to keep isolated on site.
Laboured or fast breathing at rest
Nostril flare, obvious abdominal effort, noisy breathing (stridor), or respiratory rate persistently elevated with discharge.
Fever with discharge
Adult temperature >101.5 °F (38.6 °C)—urgent; ≥104.0 °F (≥40.0 °C) is an emergency. Any fever with discharge in a foal is urgent.
Foul odour or bloody/thick unilateral discharge
Malodour, blood, or thick pus from one nostril with facial/sinus pain or swelling suggests sinus or tooth-root disease—call now.
Difficulty swallowing or feed/water from nose
Dysphagia or nasal reflux requires prompt veterinary assessment to prevent aspiration and address underlying causes.
Foal or late-term broodmare
Cough/discharge in foals (especially with fever or poor nursing) and late-term mares warrants urgent evaluation.
Recent travel or known barn cases
New arrivals, shows/transport, or active strangles/respiratory cases raise outbreak risk—strict isolation and immediate veterinary advice.
Likely Causes of Nasal Discharge by Context
These patterns help you and your veterinarian discuss likely differentials. Only a vet can diagnose; use isolation and biosecurity if fever, thick/purulent discharge, or cough is present.
Viral respiratory infection
Common in boarding barns and after travel. Clear to white discharge may precede cough and fever; spreads easily by close contact and shared equipment.
Strangles (Streptococcus equi)
Highly contagious. Fever often comes first, followed by thick yellow discharge and swollen lymph nodes under the jaw. Strict isolation and separate water sources are essential.
Sinusitis / dental tooth-root disease
Usually a foul-smelling, thick or blood-tinged unilateral discharge. Can follow a maxillary cheek-tooth infection or sinus cyst; facial pain or swelling may occur.
Dust/irritant exposure (IAD/RAO context)
Clear discharge with coughing or wheeze in dusty barns or when feeding dry hay. Improves with soaked/steamed hay and better ventilation; fever is uncommon.
Guttural pouch disease (empyema/mycosis)
Nasal discharge with cough or swallowing issues. Mycosis can bleed; empyema can follow strangles. Needs prompt veterinary evaluation.
Recent choke (esophageal obstruction) aftermath
Feed or water may reflux from the nostrils during/after an episode. Risk of aspiration pneumonia—veterinary follow-up is important.
What to Tell Your Veterinarian
Share concise, time-stamped facts. These details help your vet judge urgency, biosecurity risk, and next steps. Avoid medications unless your veterinarian directs you.
Exact rectal temperatures with times. Adult fever is >101.5 °F (38.6 °C); ≥104.0 °F (≥40.0 °C) is an emergency.
Colour (clear/white/yellow–green/bloody), thickness, odour, volume, unilateral vs bilateral. Include photos if safe.
Rate at rest, nostril flare, noise (stridor), abdominal effort, presence and frequency of cough.
Recent shows/transport, new arrivals, shared water sources, or known cases at the barn (e.g., strangles).
Quidding, feed packing, foul odour, facial pain/swelling, recent dental work, or any choke episode.
Recent vaccinations (WNV, EHV/EIV), NSAIDs/antibiotics, supplements or dewormers with dates/doses if known.
Horse Nasal Discharge FAQ: Fast Answers for Owners
When is nasal discharge an emergency?
If breathing is laboured or fast at rest, discharge is bloody or foul-smelling with facial pain, fever ≥104.0 °F (≥40.0 °C), or a foal is affected—seek veterinary care immediately.
Is clear discharge always harmless?
Not always. Dust or mild viral illness can cause clear discharge, but worsening effort, fever, cough, or thick/odorous secretions require veterinary advice.
Do I need to isolate my horse?
Yes if fever, cough, or thick/yellow-green discharge is present, or if there are known barn cases. Use separate buckets and tools and handle this horse last.
Could teeth cause one-sided discharge?
Yes. Tooth-root infections and sinus disease often cause unilateral, foul-smelling discharge and may need imaging and dental/sinus treatment.
What can I do while waiting for the vet?
Log vitals every 2–4 hours, reduce dust (soaked/steamed hay, ventilation), keep the head in a natural position to aid drainage, and maintain isolation if indicated.
Should I start antibiotics?
Do not start medications unless your veterinarian directs you. Some infections are viral or need targeted therapy based on exam and testing.
Useful links
Owner-safe references to use while you log vitals, describe the discharge, and arrange veterinary advice.