TL;DR: Green discharge from only one nostril suggests a localized issue like an infection or foreign object and requires a veterinary exam within 24 to 48 hours.
What does it mean if my dog has green discharge from one nostril?
Green mucus coming from only one nostril (unilateral discharge) is a sign that your dog is dealing with an active inflammatory or infectious process. While clear discharge is often just allergies, thick green or yellow discharge indicates the presence of white blood cells and potentially bacteria. Because it is only on one side, it suggests the problem is localized—common causes include a foreign object stuck in the nasal passage (like a grass seed), a fungal infection, a tooth root abscess affecting the sinus, or a nasal polyp.
Is unilateral green nasal discharge an emergency for my dog?
- The urgency level for this symptom is Medium; while not a life-threatening emergency, it will not resolve on its own.
- You should schedule a veterinary appointment within 24 to 48 hours.
- Seek care as soon as possible if you notice facial swelling, constant sneezing, or if your dog stops eating.
How can taking a photo of my dog's nose help the veterinarian?
- A photo allows the medical team to see the exact color, thickness, and volume of the mucus before your dog sneezes it away or licks it off.
- A photo of your dog's face from the front can help the vet identify subtle facial asymmetry or swelling.
- Visual evidence helps the vet differentiate between dental issues, foreign bodies, or growths inside the nasal cavity.
Clinical Context (Merck Veterinary Manual)
An acute unilateral nasal discharge, especially if accompanied by pawing at the face, suggests a nasal foreign body. A chronic nasal discharge that was initially unilateral but becomes bilateral, or changes in character from mucopurulent to serosanguineous or hemorrhagic, may suggest neoplastic or mycotic disease. Head shyness or facial pain is more commonly associated with fungal rhinitis in dogs. Diagnostics should include a thorough history, physical examination, and imaging of the nasal chambers via radiographs or CT. Rhinoscopy, retroflex nasopharyngoscopy, nasal flushing, and nasal biopsy may be necessary but should be delayed until after imaging to avoid iatrogenic changes. Consider CBC, serum chemistry profile, and urinalysis to exclude concurrent systemic disease. If epistaxis is present, consider one-stage prothrombin time, partial thromboplastin time, and buccal mucosal bleeding time in addition to a platelet count.
Chapter: Respiratory, Infectious Diseases, Neoplasia, Fungal
Source: The Merck Veterinary Manual, 11th Edition (Page 1489)