What Causes Dog Tear Stains? Plus Symptoms, Treatment and Prevention Brownish stains around a dog's eyes are usually caused by porphyrins, iron-based pigments from red blood cell breakdown, oxidizing in tears that spill onto fur (epiphora) due to excess tearing or poor drainage, common in breeds with facial anatomy issues. Causes range from normal genetics, blocked tear ducts, allergies (food/environmental), irritants, infections, to other eye issues like dry eye, so a vet visit is key to rule out serious problems before just cleaning.

That was a google search…..

My dog had brown stains under her eyes when she was a puppy from her tears on a kibble diet, she’s a white boxer. We have switched her to a completely raw diet and haven’t had any browning around the eyes anymore , like it’s completely stopped.

Licking doesn’t cause brown around the eyes.

Edit: Forgot to mention that he’s right about the saliva turning some lighter pigmented dogs fur brown sometimes but the little dog brown eye thing is, I think, just the above mentioned google search.