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Why Does My Dog Have Tear Stains?

Posted March 08, 2015 in Dog Diseases & Conditions A-Z

Poodle with tear stains

Have you ever noticed how many dogs have reddish brown staining of their fur? It occurs most commonly where tears moisten the fur around the dog’s eyes or around their mouth where saliva wets their fur as well as where they lick their feet and forelegs.

What is causing the stains in dogs?
This discoloration is caused by a chemical called porphyrin. Porphyrins are excreted primarily through bile and the intestinal tract, but in dogs a significant amount of porphyrin is excreted through tears, saliva and also urine. Saliva and tears contain substances called porphyrins, which stain light fur pink, red or brown. Porphyrins are a group of organic compounds of which many occur in nature. One of the best-known porphyrins is heme, the pigment in red blood cells. If you have ever noticed a white dog that has been licking or chewing on his leg, the hair in that area will turn iron-brown in color. The actual cause of stains is the porphyrin in the tears and saliva.

Why do stains occur in dogs?
Some dogs produce excessive tears – primarily because when humans turned wolves into today's best friend selective breeding created short noses and protruding eyes that contribute to abnormally narrow and often crooked tear ducts. Some medical conditions that result in excess tearing and licking are associated with the excess staining but are not the cause of the stain. In addition to allergies and irritants that may cause excess licking, anatomical problems such as ingrown eyelashes, entropion, abnormally small tear duct openings and irritants such as cigarette smoke may be causes1.

When porphyrins remain in contact with hair, particularly in white coats, for any time, the chemical stain develops. It is virtually impossible to remove once it develops.

Is porphyrin staining serious in dogs?
Fortunately, porphyrin staining is in itself a cosmetic problem and causes the dog no harm. However, the underlying or causative problem can be significant. Eyelid abnormalities may cause significant discomfort. Excess salivation may be caused by oral discomfort such as gum disease or dental problems. And dogs that lick and scratch their faces, feet, armpits and genitals frequently are affected by allergies that can cause distress.

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Mike has more than 35 years of experience in companion animal veterinary practice and is a valued member of IDEXX’s Pet Health Network team since 2013.