What causes brown tear stains under my dog's eyes?

Tears naturally contain a compound that reacts with air and light over time, turning the fur it sits on a rust or reddish brown color, a process that takes days to weeks of consistent moisture rather than happening overnight after one teary episode.

Flat faced breeds and those with prominent, slightly protruding eyes, like Shih Tzus or Pugs, often have tear ducts that drain less efficiently, leading to more overflow onto the face. Light or white coated dogs simply show the resulting staining far more visibly than dogs with darker fur, even at similar tear volumes.

Wiping the area daily with a clean, damp cloth slows new staining from building up, and keeping the fur trimmed short under the eyes reduces how much surface area is available for staining to show. Existing staining fades gradually as new, unstained fur grows in over several weeks.

Some owners report that switching to a higher quality diet or addressing a possible food sensitivity coincides with reduced staining, though the evidence connecting diet directly to tear stain severity is mixed and results vary between individual dogs, so this is worth discussing with your vet rather than assuming a diet change alone will resolve significant staining.

Stress and changes in routine can occasionally cause a temporary uptick in tearing for some dogs, similar to how emotional stress can affect tear production in people, so a stressful period, like a house move, might coincide with slightly more noticeable staining for a few weeks.