TL;DR: Tear staining is typically a cosmetic issue caused by oxidized porphyrins in tears, but you should consult a vet if your dog shows signs of pain, redness, or squinting.
What causes reddish-brown tear stains under my dog's eyes?
Excessive tearing, medically known as epiphora, often leads to the development of reddish-brown or rust-colored stains beneath a dog's eyes. This discoloration is primarily caused by porphyrins, which are iron-containing molecules produced when the body breaks down iron. These molecules are excreted through tears, saliva, and urine. When they remain on the fur and are exposed to oxygen, they oxidize and create that characteristic copper tint.
When is dog tear staining considered a medical emergency?
While simple tear staining is usually a low-urgency cosmetic issue, you should schedule a veterinary appointment within 24 to 48 hours if you notice:
- Squinting or holding the eye shut
- Pawing at the eye
- Changes in the color of the eye, such as cloudiness or deep redness
- Signs of pain or discomfort
- Significant swelling around the eye area
How does a photo of my dog's eyes help with veterinary triage?
Sharing a high-quality photo is incredibly helpful for triage because it allows a professional to evaluate:
- The exact location and extent of the staining
- The texture and consistency of the discharge
- Whether the surrounding skin is inflamed
- If the eye globe itself looks healthy
- The presence of structural abnormalities, such as inward-rolling eyelids
Clinical Context (Merck Veterinary Manual)
In dogs, tear staining (epiphora) can result from several causes, including imperforate lacrimal puncta, particularly in young animals. Obstructions within the tear drainage system may necessitate dacryocystorhinography to identify the site and cause. Treatment focuses on maintaining duct patency using topical antibiotics and temporary catheterization with polyethylene or silicone tubing or monofilament nylon suture. Irreversible damage to the nasolacrimal apparatus may require surgical intervention, such as conjunctivorhinostomy or conjunctivoralostomy, to create a new drainage pathway.
Chapter: Ophthalmology
Source: The Merck Veterinary Manual, 11th Edition (Page 490)