Nasal Discharge in Horses by a Vet – 2025 Guide to Blood, Pus, Fungal Infection & Sinus Disease 🐴👃

By Dr Duncan Houston, BVSc

Introduction

Nasal discharge in horses is a common concern among owners and trainers—but it can range from completely harmless to urgently life-threatening. In 2025, we know that understanding the type, volume, and color of discharge is key to identifying whether your horse has a simple cold, a sinus infection, or a serious condition like guttural pouch disease or a fungal bleed.

Types of Nasal Discharge and Their Meaning 🔍

1. Clear or Serous Discharge

• Often due to dust, allergens, or mild irritation
• Usually resolves on its own without treatment

2. Bloody Discharge (Epistaxis)

Not all nosebleeds are equal. Some are mild and self-limiting. Others are emergencies.

Common Causes:

• Exercise-Induced Pulmonary Hemorrhage (EIPH):
  • Seen in performance horses post-event
  • Small drops of blood at the nostrils
  • Rarely serious, unless repeated frequently
• Trauma:
  • Blunt trauma to the face or head can cause bleeding
  • Usually mild and resolves without intervention
• Progressive Ethmoidal Hematoma:
  • Causes intermittent bleeding from one nostril
  • Can be removed surgically or with injections
• Fungal Infection of Nasal Cavity:
  • Extremely serious
  • Can erode into major blood vessels and cause fatal hemorrhage
  • Large volume blood loss = Emergency surgery needed

3. Purulent Discharge (Pus – Yellow or Green)

Pus usually indicates a bacterial infection. The location of the infection determines treatment.

Common Causes:

• Upper Respiratory Infection:
  • Mild to moderate discharge, may respond to antibiotics
• Guttural Pouch Infection:
  • Thick pus with foul odor
  • Common in horses with strangles
  • Requires flushing through a catheter; antibiotics alone often fail
• Sinus Infection:
  • May be from primary bacterial infection or dental disease
  • Discharge may drain unilaterally from one nostril
  • Requires sinus flush through a bone flap or drilled hole

Diagnostic Tools 🩺

1. Endoscopy (Nasal Scope)

• Allows visual inspection of:
  • Guttural pouches
  • Sinus openings
  • Ethmoid region
• Essential for pinpointing bleeds or chronic infection

2. Skull Radiographs or CT Scan

• Used to locate sinus masses, fluid, or dental root infections

3. Dental Examination

• Especially important if unilateral pus or chronic odor is present
• Dental abscesses can drain into the sinus cavity

Treatment Based on Cause 💊

• Bacterial Infections: Often require local flushing and systemic antibiotics
• Fungal Infections: Require surgical or endoscopic removal + antifungal treatment
• Ethmoid Hematomas: Treated with laser or formalin injections
• Dental/Sinus Disease: May need sinus surgery + dental extraction

Case Example: Mare with Chronic One-Sided Pus

1. 7-year-old mare had green pus from right nostril for 3 weeks
2. No response to antibiotics
3. Endoscopy revealed pus in maxillary sinus
4. Skull x-ray showed dental root abscess
5. Surgery performed to extract molar and flush sinus
6. Complete resolution after 2 weeks

FAQs About Nasal Discharge in Horses

Q: When should I worry about nosebleeds?

A: Always call your vet for nosebleeds. Minor EIPH is common, but large or chronic bleeding could be life-threatening.

Q: Can strangles cause nasal discharge?

A: Yes. Strangles frequently infects the guttural pouch and can lead to thick, purulent drainage.

Q: Why does only one nostril have pus?

A: Unilateral discharge typically means the infection is localized to one sinus or nasal passage.

Conclusion

Nasal discharge in horses can be a simple annoyance—or a sign of a deeper health issue. In 2025, veterinarians know how to differentiate harmless mucus from serious infections, tumors, or bleeding events. If your horse has blood, pus, chronic drainage, or foul odor from one or both nostrils, it’s time to investigate with scoping and diagnostics.

Concerned about nasal discharge or facial swelling in your horse? Visit AskAVet.com or download our app 📱 to consult Dr Duncan Houston for personalized respiratory and sinus evaluations. 🩺🐴